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the end of the world y2k . the rapture . 2012 . for over a decade , speculation about the end of the world has run rampant—all in conjunction with the arrival of the new millennium . the same was true for our religious european counterparts who , prior to the year 1000 , believed the second coming of christ was imminent , and the end was nigh . when the apocalypse failed to materialize in 1000 , it was decided that the correct year must be 1033 , a thousand years from the death of jesus christ , but then that year also passed without any cataclysmic event . just how extreme the millennial panic was , remains debated . it is certain that from the year 950 onwards , there was a significant increase in building activity , particularly of religious structures . there were many reasons for this construction boom beside millennial panic , and the building of monumental religious structures continued even as fears of the immediate end of time faded . not surprisingly , this period also witnessed a surge in the popularity of the religious pilgrimage . a pilgrimage is a journey to a sacred place . these are acts of piety and may have been undertaken in gratitude for the fact that doomsday had not arrived , and to ensure salvation , whenever the end did come . the pilgrimage to santiago de compostela for the average european in the 12th century , a pilgrimage to the holy land of jerusalem was out of the question—travel to the middle east was too far , too dangerous and too expensive . santiago de compostela in spain offered a much more convenient option . to this day , hundreds of thousands of faithful travel the “ way of saint james ” to the spanish city of santiago de compostela . they go on foot across europe to a holy shrine where bones , believed to belong to saint james , were unearthed . the cathedral of santiago de compostela now stands on this site . the pious of the middle ages wanted to pay homage to holy relics , and pilgrimage churches sprang up along the route to spain . pilgrims commonly walked barefoot and wore a scalloped shell , the symbol of saint james ( the shell 's grooves symbolize the many roads of the pilgrimage ) . in france alone there were four main routes toward spain . le puy , arles , paris and vézelay are the cities on these roads and each contains a church that was an important prilgrimage site in its own right . why make a pilgrimage ? a pilgrimage to santiago de compostela was an expression of christian devotion and it was believed that it could purify the soul and perhaps even produce miraculous healing benefits . a criminal could travel the `` way of saint james '' as an act penance . for the everyday person , a pilgrimage was also one of the only opportunities to travel and see some of the world . it was a chance to meet people , perhaps even those outside one 's own class . the purpose of pilgrimage may not have been entirely devotional . the cult of the relic pilgrimage churches can be seen in part as popular desinations , a spiritual tourism of sorts for medieval travelers . guidebooks , badges and various souvenirs were sold . pilgrims , though traveling light , would spend money in the towns that possessed important sacred relics . the cult of relic was at its peak during the romanesque period ( c. 1000 - 1200 ) . relics are religious objects generally connected to a saint , or some other venerated person . a relic might be a body part , a saint 's finger , a cloth worn by the virgin mary , or a piece of the true cross . relics are often housed in a protective container called a reliquary . reliquarys are often quite opulent and can be encrusted with precious metals and gemstones given by the faithful . an example is the reliquary of saint foy , located at conques abbey on the pilgrimage route . it is said to hold a piece of the child martyr ’ s skull . a large pilgrimage church might be home to one major relic , and dozens of lesser-known relics . because of their sacred and economic value , every church wanted an important relic and a black market boomed with fake and stolen goods . accomodating crowds pilgrimage churches were constructed with some special features to make them particularly accessible to visitors . the goal was to get large numbers of people to the relics and out again without disturbing the mass in the center of the church . a large portal that could accommodate the pious throngs was a prerequisite . generally , these portals would also have an elaborate sculptural program , often portraying the second coming—a good way to remind the weary pilgrim why they made the trip ! a pilgrimage church generally consisted of a double aisle on either side of the nave ( the wide hall that runs down the center of a church ) . in this way , the visitor could move easily around the outer edges of the church until reaching the smaller apsidioles or radiating chapels . these are small rooms generally located off the back of the church behind the altar where relics were often displayed . the faithful would move from chapel to chapel venerating each relic in turn . thick walls , small windows romanesque churches were dark . this was in large part because of the use of stone barrel-vault construction . this system provided excellent acoustics and reduced fire danger . however , a barrel vault exerts continuous lateral ( outward pressure ) all along the walls that support the vault . this meant the outer walls of the church had to be extra thick . it also meant that windows had to be small and few . when builders dared to pierce walls with additional or larger windows they risked structural failure . churches did collapse . later , the masons of the gothic period replaced the barrel vault with the groin vault which carries weight down to its four corners , concentrating the pressure of the vaulting , and allowing for much larger windows . essay by christine m. bolli
|
a pilgrimage to santiago de compostela was an expression of christian devotion and it was believed that it could purify the soul and perhaps even produce miraculous healing benefits . a criminal could travel the `` way of saint james '' as an act penance . for the everyday person , a pilgrimage was also one of the only opportunities to travel and see some of the world .
|
are they just remnants of cultures long ago ( the way that current religious holidays correlate strongly with past pagan holidays ) , or perhaps just propagated by individuals who perceive a degradation of morals in their societies and desire divine judgement ?
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the end of the world y2k . the rapture . 2012 . for over a decade , speculation about the end of the world has run rampant—all in conjunction with the arrival of the new millennium . the same was true for our religious european counterparts who , prior to the year 1000 , believed the second coming of christ was imminent , and the end was nigh . when the apocalypse failed to materialize in 1000 , it was decided that the correct year must be 1033 , a thousand years from the death of jesus christ , but then that year also passed without any cataclysmic event . just how extreme the millennial panic was , remains debated . it is certain that from the year 950 onwards , there was a significant increase in building activity , particularly of religious structures . there were many reasons for this construction boom beside millennial panic , and the building of monumental religious structures continued even as fears of the immediate end of time faded . not surprisingly , this period also witnessed a surge in the popularity of the religious pilgrimage . a pilgrimage is a journey to a sacred place . these are acts of piety and may have been undertaken in gratitude for the fact that doomsday had not arrived , and to ensure salvation , whenever the end did come . the pilgrimage to santiago de compostela for the average european in the 12th century , a pilgrimage to the holy land of jerusalem was out of the question—travel to the middle east was too far , too dangerous and too expensive . santiago de compostela in spain offered a much more convenient option . to this day , hundreds of thousands of faithful travel the “ way of saint james ” to the spanish city of santiago de compostela . they go on foot across europe to a holy shrine where bones , believed to belong to saint james , were unearthed . the cathedral of santiago de compostela now stands on this site . the pious of the middle ages wanted to pay homage to holy relics , and pilgrimage churches sprang up along the route to spain . pilgrims commonly walked barefoot and wore a scalloped shell , the symbol of saint james ( the shell 's grooves symbolize the many roads of the pilgrimage ) . in france alone there were four main routes toward spain . le puy , arles , paris and vézelay are the cities on these roads and each contains a church that was an important prilgrimage site in its own right . why make a pilgrimage ? a pilgrimage to santiago de compostela was an expression of christian devotion and it was believed that it could purify the soul and perhaps even produce miraculous healing benefits . a criminal could travel the `` way of saint james '' as an act penance . for the everyday person , a pilgrimage was also one of the only opportunities to travel and see some of the world . it was a chance to meet people , perhaps even those outside one 's own class . the purpose of pilgrimage may not have been entirely devotional . the cult of the relic pilgrimage churches can be seen in part as popular desinations , a spiritual tourism of sorts for medieval travelers . guidebooks , badges and various souvenirs were sold . pilgrims , though traveling light , would spend money in the towns that possessed important sacred relics . the cult of relic was at its peak during the romanesque period ( c. 1000 - 1200 ) . relics are religious objects generally connected to a saint , or some other venerated person . a relic might be a body part , a saint 's finger , a cloth worn by the virgin mary , or a piece of the true cross . relics are often housed in a protective container called a reliquary . reliquarys are often quite opulent and can be encrusted with precious metals and gemstones given by the faithful . an example is the reliquary of saint foy , located at conques abbey on the pilgrimage route . it is said to hold a piece of the child martyr ’ s skull . a large pilgrimage church might be home to one major relic , and dozens of lesser-known relics . because of their sacred and economic value , every church wanted an important relic and a black market boomed with fake and stolen goods . accomodating crowds pilgrimage churches were constructed with some special features to make them particularly accessible to visitors . the goal was to get large numbers of people to the relics and out again without disturbing the mass in the center of the church . a large portal that could accommodate the pious throngs was a prerequisite . generally , these portals would also have an elaborate sculptural program , often portraying the second coming—a good way to remind the weary pilgrim why they made the trip ! a pilgrimage church generally consisted of a double aisle on either side of the nave ( the wide hall that runs down the center of a church ) . in this way , the visitor could move easily around the outer edges of the church until reaching the smaller apsidioles or radiating chapels . these are small rooms generally located off the back of the church behind the altar where relics were often displayed . the faithful would move from chapel to chapel venerating each relic in turn . thick walls , small windows romanesque churches were dark . this was in large part because of the use of stone barrel-vault construction . this system provided excellent acoustics and reduced fire danger . however , a barrel vault exerts continuous lateral ( outward pressure ) all along the walls that support the vault . this meant the outer walls of the church had to be extra thick . it also meant that windows had to be small and few . when builders dared to pierce walls with additional or larger windows they risked structural failure . churches did collapse . later , the masons of the gothic period replaced the barrel vault with the groin vault which carries weight down to its four corners , concentrating the pressure of the vaulting , and allowing for much larger windows . essay by christine m. bolli
|
a large pilgrimage church might be home to one major relic , and dozens of lesser-known relics . because of their sacred and economic value , every church wanted an important relic and a black market boomed with fake and stolen goods . accomodating crowds pilgrimage churches were constructed with some special features to make them particularly accessible to visitors .
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or maybe its something more systemic with the age of the society ( or just cyclic , every generation needs their own judgement day ) ?
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the end of the world y2k . the rapture . 2012 . for over a decade , speculation about the end of the world has run rampant—all in conjunction with the arrival of the new millennium . the same was true for our religious european counterparts who , prior to the year 1000 , believed the second coming of christ was imminent , and the end was nigh . when the apocalypse failed to materialize in 1000 , it was decided that the correct year must be 1033 , a thousand years from the death of jesus christ , but then that year also passed without any cataclysmic event . just how extreme the millennial panic was , remains debated . it is certain that from the year 950 onwards , there was a significant increase in building activity , particularly of religious structures . there were many reasons for this construction boom beside millennial panic , and the building of monumental religious structures continued even as fears of the immediate end of time faded . not surprisingly , this period also witnessed a surge in the popularity of the religious pilgrimage . a pilgrimage is a journey to a sacred place . these are acts of piety and may have been undertaken in gratitude for the fact that doomsday had not arrived , and to ensure salvation , whenever the end did come . the pilgrimage to santiago de compostela for the average european in the 12th century , a pilgrimage to the holy land of jerusalem was out of the question—travel to the middle east was too far , too dangerous and too expensive . santiago de compostela in spain offered a much more convenient option . to this day , hundreds of thousands of faithful travel the “ way of saint james ” to the spanish city of santiago de compostela . they go on foot across europe to a holy shrine where bones , believed to belong to saint james , were unearthed . the cathedral of santiago de compostela now stands on this site . the pious of the middle ages wanted to pay homage to holy relics , and pilgrimage churches sprang up along the route to spain . pilgrims commonly walked barefoot and wore a scalloped shell , the symbol of saint james ( the shell 's grooves symbolize the many roads of the pilgrimage ) . in france alone there were four main routes toward spain . le puy , arles , paris and vézelay are the cities on these roads and each contains a church that was an important prilgrimage site in its own right . why make a pilgrimage ? a pilgrimage to santiago de compostela was an expression of christian devotion and it was believed that it could purify the soul and perhaps even produce miraculous healing benefits . a criminal could travel the `` way of saint james '' as an act penance . for the everyday person , a pilgrimage was also one of the only opportunities to travel and see some of the world . it was a chance to meet people , perhaps even those outside one 's own class . the purpose of pilgrimage may not have been entirely devotional . the cult of the relic pilgrimage churches can be seen in part as popular desinations , a spiritual tourism of sorts for medieval travelers . guidebooks , badges and various souvenirs were sold . pilgrims , though traveling light , would spend money in the towns that possessed important sacred relics . the cult of relic was at its peak during the romanesque period ( c. 1000 - 1200 ) . relics are religious objects generally connected to a saint , or some other venerated person . a relic might be a body part , a saint 's finger , a cloth worn by the virgin mary , or a piece of the true cross . relics are often housed in a protective container called a reliquary . reliquarys are often quite opulent and can be encrusted with precious metals and gemstones given by the faithful . an example is the reliquary of saint foy , located at conques abbey on the pilgrimage route . it is said to hold a piece of the child martyr ’ s skull . a large pilgrimage church might be home to one major relic , and dozens of lesser-known relics . because of their sacred and economic value , every church wanted an important relic and a black market boomed with fake and stolen goods . accomodating crowds pilgrimage churches were constructed with some special features to make them particularly accessible to visitors . the goal was to get large numbers of people to the relics and out again without disturbing the mass in the center of the church . a large portal that could accommodate the pious throngs was a prerequisite . generally , these portals would also have an elaborate sculptural program , often portraying the second coming—a good way to remind the weary pilgrim why they made the trip ! a pilgrimage church generally consisted of a double aisle on either side of the nave ( the wide hall that runs down the center of a church ) . in this way , the visitor could move easily around the outer edges of the church until reaching the smaller apsidioles or radiating chapels . these are small rooms generally located off the back of the church behind the altar where relics were often displayed . the faithful would move from chapel to chapel venerating each relic in turn . thick walls , small windows romanesque churches were dark . this was in large part because of the use of stone barrel-vault construction . this system provided excellent acoustics and reduced fire danger . however , a barrel vault exerts continuous lateral ( outward pressure ) all along the walls that support the vault . this meant the outer walls of the church had to be extra thick . it also meant that windows had to be small and few . when builders dared to pierce walls with additional or larger windows they risked structural failure . churches did collapse . later , the masons of the gothic period replaced the barrel vault with the groin vault which carries weight down to its four corners , concentrating the pressure of the vaulting , and allowing for much larger windows . essay by christine m. bolli
|
the end of the world y2k . the rapture .
|
only god can predict the end of the world , the question is when ?
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the end of the world y2k . the rapture . 2012 . for over a decade , speculation about the end of the world has run rampant—all in conjunction with the arrival of the new millennium . the same was true for our religious european counterparts who , prior to the year 1000 , believed the second coming of christ was imminent , and the end was nigh . when the apocalypse failed to materialize in 1000 , it was decided that the correct year must be 1033 , a thousand years from the death of jesus christ , but then that year also passed without any cataclysmic event . just how extreme the millennial panic was , remains debated . it is certain that from the year 950 onwards , there was a significant increase in building activity , particularly of religious structures . there were many reasons for this construction boom beside millennial panic , and the building of monumental religious structures continued even as fears of the immediate end of time faded . not surprisingly , this period also witnessed a surge in the popularity of the religious pilgrimage . a pilgrimage is a journey to a sacred place . these are acts of piety and may have been undertaken in gratitude for the fact that doomsday had not arrived , and to ensure salvation , whenever the end did come . the pilgrimage to santiago de compostela for the average european in the 12th century , a pilgrimage to the holy land of jerusalem was out of the question—travel to the middle east was too far , too dangerous and too expensive . santiago de compostela in spain offered a much more convenient option . to this day , hundreds of thousands of faithful travel the “ way of saint james ” to the spanish city of santiago de compostela . they go on foot across europe to a holy shrine where bones , believed to belong to saint james , were unearthed . the cathedral of santiago de compostela now stands on this site . the pious of the middle ages wanted to pay homage to holy relics , and pilgrimage churches sprang up along the route to spain . pilgrims commonly walked barefoot and wore a scalloped shell , the symbol of saint james ( the shell 's grooves symbolize the many roads of the pilgrimage ) . in france alone there were four main routes toward spain . le puy , arles , paris and vézelay are the cities on these roads and each contains a church that was an important prilgrimage site in its own right . why make a pilgrimage ? a pilgrimage to santiago de compostela was an expression of christian devotion and it was believed that it could purify the soul and perhaps even produce miraculous healing benefits . a criminal could travel the `` way of saint james '' as an act penance . for the everyday person , a pilgrimage was also one of the only opportunities to travel and see some of the world . it was a chance to meet people , perhaps even those outside one 's own class . the purpose of pilgrimage may not have been entirely devotional . the cult of the relic pilgrimage churches can be seen in part as popular desinations , a spiritual tourism of sorts for medieval travelers . guidebooks , badges and various souvenirs were sold . pilgrims , though traveling light , would spend money in the towns that possessed important sacred relics . the cult of relic was at its peak during the romanesque period ( c. 1000 - 1200 ) . relics are religious objects generally connected to a saint , or some other venerated person . a relic might be a body part , a saint 's finger , a cloth worn by the virgin mary , or a piece of the true cross . relics are often housed in a protective container called a reliquary . reliquarys are often quite opulent and can be encrusted with precious metals and gemstones given by the faithful . an example is the reliquary of saint foy , located at conques abbey on the pilgrimage route . it is said to hold a piece of the child martyr ’ s skull . a large pilgrimage church might be home to one major relic , and dozens of lesser-known relics . because of their sacred and economic value , every church wanted an important relic and a black market boomed with fake and stolen goods . accomodating crowds pilgrimage churches were constructed with some special features to make them particularly accessible to visitors . the goal was to get large numbers of people to the relics and out again without disturbing the mass in the center of the church . a large portal that could accommodate the pious throngs was a prerequisite . generally , these portals would also have an elaborate sculptural program , often portraying the second coming—a good way to remind the weary pilgrim why they made the trip ! a pilgrimage church generally consisted of a double aisle on either side of the nave ( the wide hall that runs down the center of a church ) . in this way , the visitor could move easily around the outer edges of the church until reaching the smaller apsidioles or radiating chapels . these are small rooms generally located off the back of the church behind the altar where relics were often displayed . the faithful would move from chapel to chapel venerating each relic in turn . thick walls , small windows romanesque churches were dark . this was in large part because of the use of stone barrel-vault construction . this system provided excellent acoustics and reduced fire danger . however , a barrel vault exerts continuous lateral ( outward pressure ) all along the walls that support the vault . this meant the outer walls of the church had to be extra thick . it also meant that windows had to be small and few . when builders dared to pierce walls with additional or larger windows they risked structural failure . churches did collapse . later , the masons of the gothic period replaced the barrel vault with the groin vault which carries weight down to its four corners , concentrating the pressure of the vaulting , and allowing for much larger windows . essay by christine m. bolli
|
the end of the world y2k . the rapture .
|
why would jesus ' return be an end ?
|
the end of the world y2k . the rapture . 2012 . for over a decade , speculation about the end of the world has run rampant—all in conjunction with the arrival of the new millennium . the same was true for our religious european counterparts who , prior to the year 1000 , believed the second coming of christ was imminent , and the end was nigh . when the apocalypse failed to materialize in 1000 , it was decided that the correct year must be 1033 , a thousand years from the death of jesus christ , but then that year also passed without any cataclysmic event . just how extreme the millennial panic was , remains debated . it is certain that from the year 950 onwards , there was a significant increase in building activity , particularly of religious structures . there were many reasons for this construction boom beside millennial panic , and the building of monumental religious structures continued even as fears of the immediate end of time faded . not surprisingly , this period also witnessed a surge in the popularity of the religious pilgrimage . a pilgrimage is a journey to a sacred place . these are acts of piety and may have been undertaken in gratitude for the fact that doomsday had not arrived , and to ensure salvation , whenever the end did come . the pilgrimage to santiago de compostela for the average european in the 12th century , a pilgrimage to the holy land of jerusalem was out of the question—travel to the middle east was too far , too dangerous and too expensive . santiago de compostela in spain offered a much more convenient option . to this day , hundreds of thousands of faithful travel the “ way of saint james ” to the spanish city of santiago de compostela . they go on foot across europe to a holy shrine where bones , believed to belong to saint james , were unearthed . the cathedral of santiago de compostela now stands on this site . the pious of the middle ages wanted to pay homage to holy relics , and pilgrimage churches sprang up along the route to spain . pilgrims commonly walked barefoot and wore a scalloped shell , the symbol of saint james ( the shell 's grooves symbolize the many roads of the pilgrimage ) . in france alone there were four main routes toward spain . le puy , arles , paris and vézelay are the cities on these roads and each contains a church that was an important prilgrimage site in its own right . why make a pilgrimage ? a pilgrimage to santiago de compostela was an expression of christian devotion and it was believed that it could purify the soul and perhaps even produce miraculous healing benefits . a criminal could travel the `` way of saint james '' as an act penance . for the everyday person , a pilgrimage was also one of the only opportunities to travel and see some of the world . it was a chance to meet people , perhaps even those outside one 's own class . the purpose of pilgrimage may not have been entirely devotional . the cult of the relic pilgrimage churches can be seen in part as popular desinations , a spiritual tourism of sorts for medieval travelers . guidebooks , badges and various souvenirs were sold . pilgrims , though traveling light , would spend money in the towns that possessed important sacred relics . the cult of relic was at its peak during the romanesque period ( c. 1000 - 1200 ) . relics are religious objects generally connected to a saint , or some other venerated person . a relic might be a body part , a saint 's finger , a cloth worn by the virgin mary , or a piece of the true cross . relics are often housed in a protective container called a reliquary . reliquarys are often quite opulent and can be encrusted with precious metals and gemstones given by the faithful . an example is the reliquary of saint foy , located at conques abbey on the pilgrimage route . it is said to hold a piece of the child martyr ’ s skull . a large pilgrimage church might be home to one major relic , and dozens of lesser-known relics . because of their sacred and economic value , every church wanted an important relic and a black market boomed with fake and stolen goods . accomodating crowds pilgrimage churches were constructed with some special features to make them particularly accessible to visitors . the goal was to get large numbers of people to the relics and out again without disturbing the mass in the center of the church . a large portal that could accommodate the pious throngs was a prerequisite . generally , these portals would also have an elaborate sculptural program , often portraying the second coming—a good way to remind the weary pilgrim why they made the trip ! a pilgrimage church generally consisted of a double aisle on either side of the nave ( the wide hall that runs down the center of a church ) . in this way , the visitor could move easily around the outer edges of the church until reaching the smaller apsidioles or radiating chapels . these are small rooms generally located off the back of the church behind the altar where relics were often displayed . the faithful would move from chapel to chapel venerating each relic in turn . thick walls , small windows romanesque churches were dark . this was in large part because of the use of stone barrel-vault construction . this system provided excellent acoustics and reduced fire danger . however , a barrel vault exerts continuous lateral ( outward pressure ) all along the walls that support the vault . this meant the outer walls of the church had to be extra thick . it also meant that windows had to be small and few . when builders dared to pierce walls with additional or larger windows they risked structural failure . churches did collapse . later , the masons of the gothic period replaced the barrel vault with the groin vault which carries weight down to its four corners , concentrating the pressure of the vaulting , and allowing for much larger windows . essay by christine m. bolli
|
accomodating crowds pilgrimage churches were constructed with some special features to make them particularly accessible to visitors . the goal was to get large numbers of people to the relics and out again without disturbing the mass in the center of the church . a large portal that could accommodate the pious throngs was a prerequisite .
|
can you give me a quote about the many people visiting relics ?
|
the end of the world y2k . the rapture . 2012 . for over a decade , speculation about the end of the world has run rampant—all in conjunction with the arrival of the new millennium . the same was true for our religious european counterparts who , prior to the year 1000 , believed the second coming of christ was imminent , and the end was nigh . when the apocalypse failed to materialize in 1000 , it was decided that the correct year must be 1033 , a thousand years from the death of jesus christ , but then that year also passed without any cataclysmic event . just how extreme the millennial panic was , remains debated . it is certain that from the year 950 onwards , there was a significant increase in building activity , particularly of religious structures . there were many reasons for this construction boom beside millennial panic , and the building of monumental religious structures continued even as fears of the immediate end of time faded . not surprisingly , this period also witnessed a surge in the popularity of the religious pilgrimage . a pilgrimage is a journey to a sacred place . these are acts of piety and may have been undertaken in gratitude for the fact that doomsday had not arrived , and to ensure salvation , whenever the end did come . the pilgrimage to santiago de compostela for the average european in the 12th century , a pilgrimage to the holy land of jerusalem was out of the question—travel to the middle east was too far , too dangerous and too expensive . santiago de compostela in spain offered a much more convenient option . to this day , hundreds of thousands of faithful travel the “ way of saint james ” to the spanish city of santiago de compostela . they go on foot across europe to a holy shrine where bones , believed to belong to saint james , were unearthed . the cathedral of santiago de compostela now stands on this site . the pious of the middle ages wanted to pay homage to holy relics , and pilgrimage churches sprang up along the route to spain . pilgrims commonly walked barefoot and wore a scalloped shell , the symbol of saint james ( the shell 's grooves symbolize the many roads of the pilgrimage ) . in france alone there were four main routes toward spain . le puy , arles , paris and vézelay are the cities on these roads and each contains a church that was an important prilgrimage site in its own right . why make a pilgrimage ? a pilgrimage to santiago de compostela was an expression of christian devotion and it was believed that it could purify the soul and perhaps even produce miraculous healing benefits . a criminal could travel the `` way of saint james '' as an act penance . for the everyday person , a pilgrimage was also one of the only opportunities to travel and see some of the world . it was a chance to meet people , perhaps even those outside one 's own class . the purpose of pilgrimage may not have been entirely devotional . the cult of the relic pilgrimage churches can be seen in part as popular desinations , a spiritual tourism of sorts for medieval travelers . guidebooks , badges and various souvenirs were sold . pilgrims , though traveling light , would spend money in the towns that possessed important sacred relics . the cult of relic was at its peak during the romanesque period ( c. 1000 - 1200 ) . relics are religious objects generally connected to a saint , or some other venerated person . a relic might be a body part , a saint 's finger , a cloth worn by the virgin mary , or a piece of the true cross . relics are often housed in a protective container called a reliquary . reliquarys are often quite opulent and can be encrusted with precious metals and gemstones given by the faithful . an example is the reliquary of saint foy , located at conques abbey on the pilgrimage route . it is said to hold a piece of the child martyr ’ s skull . a large pilgrimage church might be home to one major relic , and dozens of lesser-known relics . because of their sacred and economic value , every church wanted an important relic and a black market boomed with fake and stolen goods . accomodating crowds pilgrimage churches were constructed with some special features to make them particularly accessible to visitors . the goal was to get large numbers of people to the relics and out again without disturbing the mass in the center of the church . a large portal that could accommodate the pious throngs was a prerequisite . generally , these portals would also have an elaborate sculptural program , often portraying the second coming—a good way to remind the weary pilgrim why they made the trip ! a pilgrimage church generally consisted of a double aisle on either side of the nave ( the wide hall that runs down the center of a church ) . in this way , the visitor could move easily around the outer edges of the church until reaching the smaller apsidioles or radiating chapels . these are small rooms generally located off the back of the church behind the altar where relics were often displayed . the faithful would move from chapel to chapel venerating each relic in turn . thick walls , small windows romanesque churches were dark . this was in large part because of the use of stone barrel-vault construction . this system provided excellent acoustics and reduced fire danger . however , a barrel vault exerts continuous lateral ( outward pressure ) all along the walls that support the vault . this meant the outer walls of the church had to be extra thick . it also meant that windows had to be small and few . when builders dared to pierce walls with additional or larger windows they risked structural failure . churches did collapse . later , the masons of the gothic period replaced the barrel vault with the groin vault which carries weight down to its four corners , concentrating the pressure of the vaulting , and allowing for much larger windows . essay by christine m. bolli
|
this meant the outer walls of the church had to be extra thick . it also meant that windows had to be small and few . when builders dared to pierce walls with additional or larger windows they risked structural failure .
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also , how come you did not mention how relics had healing powers ?
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voltage and current are the cornerstone concepts in electricity . we will create our first mental models for these basic electrical quantities . we will also talk about power , which is what happens when voltage and current act together . charge the concept of electricity arises from an observation of nature . we observe a force between objects , that , like gravity , acts at a distance . the source of this force has been given the name charge . a very noticeable thing about electric force is that it is large , far greater than the force of gravity . unlike gravity , however , there are two types of electric charge . opposite types of charge attract , and like types of charge repel . gravity has only one type : it only attracts , never repels . conductors and insulators conductors are made of atoms whose outer , or valence , electrons have relatively weak bonds to their nuclei , as shown in this fanciful image of a copper atom . when a bunch of metal atoms are together , they gladly share their outer electrons with each other , creating a `` swarm '' of electrons not associated with a particular nucleus . a very small electric force can make the electron swarm move . copper , gold , silver , and aluminum are good conductors . so is saltwater . there are also poor conductors . tungsten—a metal used for light bulb filaments—and carbon—used in graphite form in pencils—are relatively poor conductors because their electrons are less prone to move . insulators are materials whose outer electrons are tightly bound to their nuclei . modest electric forces are not able to pull these electrons free . when an electric force is applied , the electron clouds around the atom stretch and deform in response to the force , but the electrons do not depart . glass , plastic , stone , and air are insulators . even for insulators , though , electric force can always be turned up high enough to rip electrons away—this is called breakdown . that 's what is happening to air molecules when you see a spark . semiconductor materials fall between insulators and conductors . they usually act like insulators , but we can make them act like conductors under certain circumstances . the most well-known semiconductor material is silicon ( atomic number $ 14 $ ) . our ability to finely control the insulating and conducting properties of silicon allows us to create modern marvels like computers and mobile phones . the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current . current is reported as the number of charges per unit time passing through a boundary . visualize placing a boundary all the way through a wire . station yourself near the boundary and count the number of charges passing by . report how much charge passed through the boundary in one second . we assign a positive sign to current corresponding to the direction a positive charge would be moving . since current is the amount of charge passing through a boundary in a fixed amount of time , it can be expressed mathematically using the following equation : $ i = \dfrac { dq } { dt } $ that 's current in a nutshell . a few remarks on current what carries current in metal ? since electrons are free to move about in metals , moving electrons are what makes up the current in metals . the positive nuclei in metal atoms are fixed in place and do not contribute to current . even though electrons have a negative charge and do almost all the work in most electric circuits , we still define a positive current as the direction a positive charge would move . this is a very old historical convention . can current be carried by positive charges ? yes . there are lots of examples . current is carried by both positive and negative charges in saltwater : if we put ordinary table salt in water , it becomes a good conductor . table salt is sodium chloride , nacl . the salt dissolves in water , into free-floating na $ ^+ $ and cl $ ^- $ ions . both ions respond to electric force and move through the saltwater solution , in opposite directions . in this case , the current is composed of moving atoms , both positive and negative ions , not just loose electrons . inside our bodies , electrical currents are moving ions , both positive and negative . the same definition of current works : count the number of charges passing by in a fixed amount of time . what causes current ? charged objects move in response to electric and magnetic forces . these forces come from electric and magnetic fields , which in turn come from the position and motion of other charges . what is the speed of current ? we do n't talk very often about the speed of current . answering the question , `` how fast is the current flowing ? '' requires understanding of a complex physical phenomenon and is not often relevant . current usually is n't about meters per second , it 's about charge per second . more often , we answer the question `` how much current is flowing ? '' all the time . how do we talk about current ? when discussing current , terms like through and in make a lot of sense . current flows through a resistor ; current flows in a wire . if you hear , `` the current across ... '' , it should sound odd . voltage to get our initial toehold on the concept of voltage , let 's look at an analogy : voltage resembles gravity for a mass $ m $ , a change of height $ h $ corresponds to a change in potential energy , $ \delta u = mg\delta h $ . for a charged particle $ q $ , a voltage $ v $ corresponds to a change in potential energy , $ \delta u = qv $ . voltage in an electric circuit is analogous to the product of $ g\cdot \delta h $ . where $ g $ is the acceleration due to gravity and $ \delta h $ is the change of height . a ball at the top of the hill rolls down . when it is halfway down , it has given up half of its potential energy . an electron at the top of a voltage `` hill '' travels `` downhill '' through wires and elements of a circuit . it gives up its potential energy , doing work along the way . when the electron is halfway down the hill , it has given up , or `` dropped '' , half of its potential energy . for both the ball and the electron , the trip down the hill happens spontaneously . the ball and electron move towards a lower energy state all by themselves . on the trip down , there can be things in the way of the ball , like trees or bears to bounce off . for electrons , we can guide electrons using wires and make them flow through electronic components —circuit design— and do interesting things along the way . we can express the voltage between two points mathematically as the change of energy experienced by a charge : $ v = \dfrac { \delta u } { q } $ that 's an intuitive description of voltage in a nutshell . power power is defined as the rate energy ( $ \text u $ ) is transformed or transferred over time . we measure power in units of joules/second , also known as watts . ( $ 1 \ , \text { watt } = 1\ , \text { joule } /\text { second } $ ) $ \text { power } = \dfrac { \text du } { \text dt } $ an electric circuit is capable of transferring power . current is the rate of flow of charge , and voltage measures the energy transferred per unit of charge . we can insert these definitions into the equation for power : $ \text { power } = \dfrac { \text du } { \text dt } = \dfrac { \text du } { \text dq } \cdot \dfrac { \text dq } { \text dt } = v \ , i $ electrical power is the product of voltage times current . in units of watts . summary these mental models for current and voltage will get us started on all sorts of interesting electric circuits . if you want to reach beyond this intuitive description of voltage you can read this more formal mathematical description of electric potential and voltage .
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opposite types of charge attract , and like types of charge repel . gravity has only one type : it only attracts , never repels . conductors and insulators conductors are made of atoms whose outer , or valence , electrons have relatively weak bonds to their nuclei , as shown in this fanciful image of a copper atom .
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if gravity never cause a repulsion force then what is anti gravity ?
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voltage and current are the cornerstone concepts in electricity . we will create our first mental models for these basic electrical quantities . we will also talk about power , which is what happens when voltage and current act together . charge the concept of electricity arises from an observation of nature . we observe a force between objects , that , like gravity , acts at a distance . the source of this force has been given the name charge . a very noticeable thing about electric force is that it is large , far greater than the force of gravity . unlike gravity , however , there are two types of electric charge . opposite types of charge attract , and like types of charge repel . gravity has only one type : it only attracts , never repels . conductors and insulators conductors are made of atoms whose outer , or valence , electrons have relatively weak bonds to their nuclei , as shown in this fanciful image of a copper atom . when a bunch of metal atoms are together , they gladly share their outer electrons with each other , creating a `` swarm '' of electrons not associated with a particular nucleus . a very small electric force can make the electron swarm move . copper , gold , silver , and aluminum are good conductors . so is saltwater . there are also poor conductors . tungsten—a metal used for light bulb filaments—and carbon—used in graphite form in pencils—are relatively poor conductors because their electrons are less prone to move . insulators are materials whose outer electrons are tightly bound to their nuclei . modest electric forces are not able to pull these electrons free . when an electric force is applied , the electron clouds around the atom stretch and deform in response to the force , but the electrons do not depart . glass , plastic , stone , and air are insulators . even for insulators , though , electric force can always be turned up high enough to rip electrons away—this is called breakdown . that 's what is happening to air molecules when you see a spark . semiconductor materials fall between insulators and conductors . they usually act like insulators , but we can make them act like conductors under certain circumstances . the most well-known semiconductor material is silicon ( atomic number $ 14 $ ) . our ability to finely control the insulating and conducting properties of silicon allows us to create modern marvels like computers and mobile phones . the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current . current is reported as the number of charges per unit time passing through a boundary . visualize placing a boundary all the way through a wire . station yourself near the boundary and count the number of charges passing by . report how much charge passed through the boundary in one second . we assign a positive sign to current corresponding to the direction a positive charge would be moving . since current is the amount of charge passing through a boundary in a fixed amount of time , it can be expressed mathematically using the following equation : $ i = \dfrac { dq } { dt } $ that 's current in a nutshell . a few remarks on current what carries current in metal ? since electrons are free to move about in metals , moving electrons are what makes up the current in metals . the positive nuclei in metal atoms are fixed in place and do not contribute to current . even though electrons have a negative charge and do almost all the work in most electric circuits , we still define a positive current as the direction a positive charge would move . this is a very old historical convention . can current be carried by positive charges ? yes . there are lots of examples . current is carried by both positive and negative charges in saltwater : if we put ordinary table salt in water , it becomes a good conductor . table salt is sodium chloride , nacl . the salt dissolves in water , into free-floating na $ ^+ $ and cl $ ^- $ ions . both ions respond to electric force and move through the saltwater solution , in opposite directions . in this case , the current is composed of moving atoms , both positive and negative ions , not just loose electrons . inside our bodies , electrical currents are moving ions , both positive and negative . the same definition of current works : count the number of charges passing by in a fixed amount of time . what causes current ? charged objects move in response to electric and magnetic forces . these forces come from electric and magnetic fields , which in turn come from the position and motion of other charges . what is the speed of current ? we do n't talk very often about the speed of current . answering the question , `` how fast is the current flowing ? '' requires understanding of a complex physical phenomenon and is not often relevant . current usually is n't about meters per second , it 's about charge per second . more often , we answer the question `` how much current is flowing ? '' all the time . how do we talk about current ? when discussing current , terms like through and in make a lot of sense . current flows through a resistor ; current flows in a wire . if you hear , `` the current across ... '' , it should sound odd . voltage to get our initial toehold on the concept of voltage , let 's look at an analogy : voltage resembles gravity for a mass $ m $ , a change of height $ h $ corresponds to a change in potential energy , $ \delta u = mg\delta h $ . for a charged particle $ q $ , a voltage $ v $ corresponds to a change in potential energy , $ \delta u = qv $ . voltage in an electric circuit is analogous to the product of $ g\cdot \delta h $ . where $ g $ is the acceleration due to gravity and $ \delta h $ is the change of height . a ball at the top of the hill rolls down . when it is halfway down , it has given up half of its potential energy . an electron at the top of a voltage `` hill '' travels `` downhill '' through wires and elements of a circuit . it gives up its potential energy , doing work along the way . when the electron is halfway down the hill , it has given up , or `` dropped '' , half of its potential energy . for both the ball and the electron , the trip down the hill happens spontaneously . the ball and electron move towards a lower energy state all by themselves . on the trip down , there can be things in the way of the ball , like trees or bears to bounce off . for electrons , we can guide electrons using wires and make them flow through electronic components —circuit design— and do interesting things along the way . we can express the voltage between two points mathematically as the change of energy experienced by a charge : $ v = \dfrac { \delta u } { q } $ that 's an intuitive description of voltage in a nutshell . power power is defined as the rate energy ( $ \text u $ ) is transformed or transferred over time . we measure power in units of joules/second , also known as watts . ( $ 1 \ , \text { watt } = 1\ , \text { joule } /\text { second } $ ) $ \text { power } = \dfrac { \text du } { \text dt } $ an electric circuit is capable of transferring power . current is the rate of flow of charge , and voltage measures the energy transferred per unit of charge . we can insert these definitions into the equation for power : $ \text { power } = \dfrac { \text du } { \text dt } = \dfrac { \text du } { \text dq } \cdot \dfrac { \text dq } { \text dt } = v \ , i $ electrical power is the product of voltage times current . in units of watts . summary these mental models for current and voltage will get us started on all sorts of interesting electric circuits . if you want to reach beyond this intuitive description of voltage you can read this more formal mathematical description of electric potential and voltage .
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if you hear , `` the current across ... '' , it should sound odd . voltage to get our initial toehold on the concept of voltage , let 's look at an analogy : voltage resembles gravity for a mass $ m $ , a change of height $ h $ corresponds to a change in potential energy , $ \delta u = mg\delta h $ . for a charged particle $ q $ , a voltage $ v $ corresponds to a change in potential energy , $ \delta u = qv $ .
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can someone please explain voltage ?
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voltage and current are the cornerstone concepts in electricity . we will create our first mental models for these basic electrical quantities . we will also talk about power , which is what happens when voltage and current act together . charge the concept of electricity arises from an observation of nature . we observe a force between objects , that , like gravity , acts at a distance . the source of this force has been given the name charge . a very noticeable thing about electric force is that it is large , far greater than the force of gravity . unlike gravity , however , there are two types of electric charge . opposite types of charge attract , and like types of charge repel . gravity has only one type : it only attracts , never repels . conductors and insulators conductors are made of atoms whose outer , or valence , electrons have relatively weak bonds to their nuclei , as shown in this fanciful image of a copper atom . when a bunch of metal atoms are together , they gladly share their outer electrons with each other , creating a `` swarm '' of electrons not associated with a particular nucleus . a very small electric force can make the electron swarm move . copper , gold , silver , and aluminum are good conductors . so is saltwater . there are also poor conductors . tungsten—a metal used for light bulb filaments—and carbon—used in graphite form in pencils—are relatively poor conductors because their electrons are less prone to move . insulators are materials whose outer electrons are tightly bound to their nuclei . modest electric forces are not able to pull these electrons free . when an electric force is applied , the electron clouds around the atom stretch and deform in response to the force , but the electrons do not depart . glass , plastic , stone , and air are insulators . even for insulators , though , electric force can always be turned up high enough to rip electrons away—this is called breakdown . that 's what is happening to air molecules when you see a spark . semiconductor materials fall between insulators and conductors . they usually act like insulators , but we can make them act like conductors under certain circumstances . the most well-known semiconductor material is silicon ( atomic number $ 14 $ ) . our ability to finely control the insulating and conducting properties of silicon allows us to create modern marvels like computers and mobile phones . the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current . current is reported as the number of charges per unit time passing through a boundary . visualize placing a boundary all the way through a wire . station yourself near the boundary and count the number of charges passing by . report how much charge passed through the boundary in one second . we assign a positive sign to current corresponding to the direction a positive charge would be moving . since current is the amount of charge passing through a boundary in a fixed amount of time , it can be expressed mathematically using the following equation : $ i = \dfrac { dq } { dt } $ that 's current in a nutshell . a few remarks on current what carries current in metal ? since electrons are free to move about in metals , moving electrons are what makes up the current in metals . the positive nuclei in metal atoms are fixed in place and do not contribute to current . even though electrons have a negative charge and do almost all the work in most electric circuits , we still define a positive current as the direction a positive charge would move . this is a very old historical convention . can current be carried by positive charges ? yes . there are lots of examples . current is carried by both positive and negative charges in saltwater : if we put ordinary table salt in water , it becomes a good conductor . table salt is sodium chloride , nacl . the salt dissolves in water , into free-floating na $ ^+ $ and cl $ ^- $ ions . both ions respond to electric force and move through the saltwater solution , in opposite directions . in this case , the current is composed of moving atoms , both positive and negative ions , not just loose electrons . inside our bodies , electrical currents are moving ions , both positive and negative . the same definition of current works : count the number of charges passing by in a fixed amount of time . what causes current ? charged objects move in response to electric and magnetic forces . these forces come from electric and magnetic fields , which in turn come from the position and motion of other charges . what is the speed of current ? we do n't talk very often about the speed of current . answering the question , `` how fast is the current flowing ? '' requires understanding of a complex physical phenomenon and is not often relevant . current usually is n't about meters per second , it 's about charge per second . more often , we answer the question `` how much current is flowing ? '' all the time . how do we talk about current ? when discussing current , terms like through and in make a lot of sense . current flows through a resistor ; current flows in a wire . if you hear , `` the current across ... '' , it should sound odd . voltage to get our initial toehold on the concept of voltage , let 's look at an analogy : voltage resembles gravity for a mass $ m $ , a change of height $ h $ corresponds to a change in potential energy , $ \delta u = mg\delta h $ . for a charged particle $ q $ , a voltage $ v $ corresponds to a change in potential energy , $ \delta u = qv $ . voltage in an electric circuit is analogous to the product of $ g\cdot \delta h $ . where $ g $ is the acceleration due to gravity and $ \delta h $ is the change of height . a ball at the top of the hill rolls down . when it is halfway down , it has given up half of its potential energy . an electron at the top of a voltage `` hill '' travels `` downhill '' through wires and elements of a circuit . it gives up its potential energy , doing work along the way . when the electron is halfway down the hill , it has given up , or `` dropped '' , half of its potential energy . for both the ball and the electron , the trip down the hill happens spontaneously . the ball and electron move towards a lower energy state all by themselves . on the trip down , there can be things in the way of the ball , like trees or bears to bounce off . for electrons , we can guide electrons using wires and make them flow through electronic components —circuit design— and do interesting things along the way . we can express the voltage between two points mathematically as the change of energy experienced by a charge : $ v = \dfrac { \delta u } { q } $ that 's an intuitive description of voltage in a nutshell . power power is defined as the rate energy ( $ \text u $ ) is transformed or transferred over time . we measure power in units of joules/second , also known as watts . ( $ 1 \ , \text { watt } = 1\ , \text { joule } /\text { second } $ ) $ \text { power } = \dfrac { \text du } { \text dt } $ an electric circuit is capable of transferring power . current is the rate of flow of charge , and voltage measures the energy transferred per unit of charge . we can insert these definitions into the equation for power : $ \text { power } = \dfrac { \text du } { \text dt } = \dfrac { \text du } { \text dq } \cdot \dfrac { \text dq } { \text dt } = v \ , i $ electrical power is the product of voltage times current . in units of watts . summary these mental models for current and voltage will get us started on all sorts of interesting electric circuits . if you want to reach beyond this intuitive description of voltage you can read this more formal mathematical description of electric potential and voltage .
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for electrons , we can guide electrons using wires and make them flow through electronic components —circuit design— and do interesting things along the way . we can express the voltage between two points mathematically as the change of energy experienced by a charge : $ v = \dfrac { \delta u } { q } $ that 's an intuitive description of voltage in a nutshell . power power is defined as the rate energy ( $ \text u $ ) is transformed or transferred over time .
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is voltage expressed as v or v ?
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voltage and current are the cornerstone concepts in electricity . we will create our first mental models for these basic electrical quantities . we will also talk about power , which is what happens when voltage and current act together . charge the concept of electricity arises from an observation of nature . we observe a force between objects , that , like gravity , acts at a distance . the source of this force has been given the name charge . a very noticeable thing about electric force is that it is large , far greater than the force of gravity . unlike gravity , however , there are two types of electric charge . opposite types of charge attract , and like types of charge repel . gravity has only one type : it only attracts , never repels . conductors and insulators conductors are made of atoms whose outer , or valence , electrons have relatively weak bonds to their nuclei , as shown in this fanciful image of a copper atom . when a bunch of metal atoms are together , they gladly share their outer electrons with each other , creating a `` swarm '' of electrons not associated with a particular nucleus . a very small electric force can make the electron swarm move . copper , gold , silver , and aluminum are good conductors . so is saltwater . there are also poor conductors . tungsten—a metal used for light bulb filaments—and carbon—used in graphite form in pencils—are relatively poor conductors because their electrons are less prone to move . insulators are materials whose outer electrons are tightly bound to their nuclei . modest electric forces are not able to pull these electrons free . when an electric force is applied , the electron clouds around the atom stretch and deform in response to the force , but the electrons do not depart . glass , plastic , stone , and air are insulators . even for insulators , though , electric force can always be turned up high enough to rip electrons away—this is called breakdown . that 's what is happening to air molecules when you see a spark . semiconductor materials fall between insulators and conductors . they usually act like insulators , but we can make them act like conductors under certain circumstances . the most well-known semiconductor material is silicon ( atomic number $ 14 $ ) . our ability to finely control the insulating and conducting properties of silicon allows us to create modern marvels like computers and mobile phones . the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current . current is reported as the number of charges per unit time passing through a boundary . visualize placing a boundary all the way through a wire . station yourself near the boundary and count the number of charges passing by . report how much charge passed through the boundary in one second . we assign a positive sign to current corresponding to the direction a positive charge would be moving . since current is the amount of charge passing through a boundary in a fixed amount of time , it can be expressed mathematically using the following equation : $ i = \dfrac { dq } { dt } $ that 's current in a nutshell . a few remarks on current what carries current in metal ? since electrons are free to move about in metals , moving electrons are what makes up the current in metals . the positive nuclei in metal atoms are fixed in place and do not contribute to current . even though electrons have a negative charge and do almost all the work in most electric circuits , we still define a positive current as the direction a positive charge would move . this is a very old historical convention . can current be carried by positive charges ? yes . there are lots of examples . current is carried by both positive and negative charges in saltwater : if we put ordinary table salt in water , it becomes a good conductor . table salt is sodium chloride , nacl . the salt dissolves in water , into free-floating na $ ^+ $ and cl $ ^- $ ions . both ions respond to electric force and move through the saltwater solution , in opposite directions . in this case , the current is composed of moving atoms , both positive and negative ions , not just loose electrons . inside our bodies , electrical currents are moving ions , both positive and negative . the same definition of current works : count the number of charges passing by in a fixed amount of time . what causes current ? charged objects move in response to electric and magnetic forces . these forces come from electric and magnetic fields , which in turn come from the position and motion of other charges . what is the speed of current ? we do n't talk very often about the speed of current . answering the question , `` how fast is the current flowing ? '' requires understanding of a complex physical phenomenon and is not often relevant . current usually is n't about meters per second , it 's about charge per second . more often , we answer the question `` how much current is flowing ? '' all the time . how do we talk about current ? when discussing current , terms like through and in make a lot of sense . current flows through a resistor ; current flows in a wire . if you hear , `` the current across ... '' , it should sound odd . voltage to get our initial toehold on the concept of voltage , let 's look at an analogy : voltage resembles gravity for a mass $ m $ , a change of height $ h $ corresponds to a change in potential energy , $ \delta u = mg\delta h $ . for a charged particle $ q $ , a voltage $ v $ corresponds to a change in potential energy , $ \delta u = qv $ . voltage in an electric circuit is analogous to the product of $ g\cdot \delta h $ . where $ g $ is the acceleration due to gravity and $ \delta h $ is the change of height . a ball at the top of the hill rolls down . when it is halfway down , it has given up half of its potential energy . an electron at the top of a voltage `` hill '' travels `` downhill '' through wires and elements of a circuit . it gives up its potential energy , doing work along the way . when the electron is halfway down the hill , it has given up , or `` dropped '' , half of its potential energy . for both the ball and the electron , the trip down the hill happens spontaneously . the ball and electron move towards a lower energy state all by themselves . on the trip down , there can be things in the way of the ball , like trees or bears to bounce off . for electrons , we can guide electrons using wires and make them flow through electronic components —circuit design— and do interesting things along the way . we can express the voltage between two points mathematically as the change of energy experienced by a charge : $ v = \dfrac { \delta u } { q } $ that 's an intuitive description of voltage in a nutshell . power power is defined as the rate energy ( $ \text u $ ) is transformed or transferred over time . we measure power in units of joules/second , also known as watts . ( $ 1 \ , \text { watt } = 1\ , \text { joule } /\text { second } $ ) $ \text { power } = \dfrac { \text du } { \text dt } $ an electric circuit is capable of transferring power . current is the rate of flow of charge , and voltage measures the energy transferred per unit of charge . we can insert these definitions into the equation for power : $ \text { power } = \dfrac { \text du } { \text dt } = \dfrac { \text du } { \text dq } \cdot \dfrac { \text dq } { \text dt } = v \ , i $ electrical power is the product of voltage times current . in units of watts . summary these mental models for current and voltage will get us started on all sorts of interesting electric circuits . if you want to reach beyond this intuitive description of voltage you can read this more formal mathematical description of electric potential and voltage .
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current is the rate of flow of charge , and voltage measures the energy transferred per unit of charge . we can insert these definitions into the equation for power : $ \text { power } = \dfrac { \text du } { \text dt } = \dfrac { \text du } { \text dq } \cdot \dfrac { \text dq } { \text dt } = v \ , i $ electrical power is the product of voltage times current . in units of watts .
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why is it written as v under `` voltage resembles gravity , '' but v in the equation v= ( du/dq ) ?
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voltage and current are the cornerstone concepts in electricity . we will create our first mental models for these basic electrical quantities . we will also talk about power , which is what happens when voltage and current act together . charge the concept of electricity arises from an observation of nature . we observe a force between objects , that , like gravity , acts at a distance . the source of this force has been given the name charge . a very noticeable thing about electric force is that it is large , far greater than the force of gravity . unlike gravity , however , there are two types of electric charge . opposite types of charge attract , and like types of charge repel . gravity has only one type : it only attracts , never repels . conductors and insulators conductors are made of atoms whose outer , or valence , electrons have relatively weak bonds to their nuclei , as shown in this fanciful image of a copper atom . when a bunch of metal atoms are together , they gladly share their outer electrons with each other , creating a `` swarm '' of electrons not associated with a particular nucleus . a very small electric force can make the electron swarm move . copper , gold , silver , and aluminum are good conductors . so is saltwater . there are also poor conductors . tungsten—a metal used for light bulb filaments—and carbon—used in graphite form in pencils—are relatively poor conductors because their electrons are less prone to move . insulators are materials whose outer electrons are tightly bound to their nuclei . modest electric forces are not able to pull these electrons free . when an electric force is applied , the electron clouds around the atom stretch and deform in response to the force , but the electrons do not depart . glass , plastic , stone , and air are insulators . even for insulators , though , electric force can always be turned up high enough to rip electrons away—this is called breakdown . that 's what is happening to air molecules when you see a spark . semiconductor materials fall between insulators and conductors . they usually act like insulators , but we can make them act like conductors under certain circumstances . the most well-known semiconductor material is silicon ( atomic number $ 14 $ ) . our ability to finely control the insulating and conducting properties of silicon allows us to create modern marvels like computers and mobile phones . the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current . current is reported as the number of charges per unit time passing through a boundary . visualize placing a boundary all the way through a wire . station yourself near the boundary and count the number of charges passing by . report how much charge passed through the boundary in one second . we assign a positive sign to current corresponding to the direction a positive charge would be moving . since current is the amount of charge passing through a boundary in a fixed amount of time , it can be expressed mathematically using the following equation : $ i = \dfrac { dq } { dt } $ that 's current in a nutshell . a few remarks on current what carries current in metal ? since electrons are free to move about in metals , moving electrons are what makes up the current in metals . the positive nuclei in metal atoms are fixed in place and do not contribute to current . even though electrons have a negative charge and do almost all the work in most electric circuits , we still define a positive current as the direction a positive charge would move . this is a very old historical convention . can current be carried by positive charges ? yes . there are lots of examples . current is carried by both positive and negative charges in saltwater : if we put ordinary table salt in water , it becomes a good conductor . table salt is sodium chloride , nacl . the salt dissolves in water , into free-floating na $ ^+ $ and cl $ ^- $ ions . both ions respond to electric force and move through the saltwater solution , in opposite directions . in this case , the current is composed of moving atoms , both positive and negative ions , not just loose electrons . inside our bodies , electrical currents are moving ions , both positive and negative . the same definition of current works : count the number of charges passing by in a fixed amount of time . what causes current ? charged objects move in response to electric and magnetic forces . these forces come from electric and magnetic fields , which in turn come from the position and motion of other charges . what is the speed of current ? we do n't talk very often about the speed of current . answering the question , `` how fast is the current flowing ? '' requires understanding of a complex physical phenomenon and is not often relevant . current usually is n't about meters per second , it 's about charge per second . more often , we answer the question `` how much current is flowing ? '' all the time . how do we talk about current ? when discussing current , terms like through and in make a lot of sense . current flows through a resistor ; current flows in a wire . if you hear , `` the current across ... '' , it should sound odd . voltage to get our initial toehold on the concept of voltage , let 's look at an analogy : voltage resembles gravity for a mass $ m $ , a change of height $ h $ corresponds to a change in potential energy , $ \delta u = mg\delta h $ . for a charged particle $ q $ , a voltage $ v $ corresponds to a change in potential energy , $ \delta u = qv $ . voltage in an electric circuit is analogous to the product of $ g\cdot \delta h $ . where $ g $ is the acceleration due to gravity and $ \delta h $ is the change of height . a ball at the top of the hill rolls down . when it is halfway down , it has given up half of its potential energy . an electron at the top of a voltage `` hill '' travels `` downhill '' through wires and elements of a circuit . it gives up its potential energy , doing work along the way . when the electron is halfway down the hill , it has given up , or `` dropped '' , half of its potential energy . for both the ball and the electron , the trip down the hill happens spontaneously . the ball and electron move towards a lower energy state all by themselves . on the trip down , there can be things in the way of the ball , like trees or bears to bounce off . for electrons , we can guide electrons using wires and make them flow through electronic components —circuit design— and do interesting things along the way . we can express the voltage between two points mathematically as the change of energy experienced by a charge : $ v = \dfrac { \delta u } { q } $ that 's an intuitive description of voltage in a nutshell . power power is defined as the rate energy ( $ \text u $ ) is transformed or transferred over time . we measure power in units of joules/second , also known as watts . ( $ 1 \ , \text { watt } = 1\ , \text { joule } /\text { second } $ ) $ \text { power } = \dfrac { \text du } { \text dt } $ an electric circuit is capable of transferring power . current is the rate of flow of charge , and voltage measures the energy transferred per unit of charge . we can insert these definitions into the equation for power : $ \text { power } = \dfrac { \text du } { \text dt } = \dfrac { \text du } { \text dq } \cdot \dfrac { \text dq } { \text dt } = v \ , i $ electrical power is the product of voltage times current . in units of watts . summary these mental models for current and voltage will get us started on all sorts of interesting electric circuits . if you want to reach beyond this intuitive description of voltage you can read this more formal mathematical description of electric potential and voltage .
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this is a very old historical convention . can current be carried by positive charges ? yes .
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what 's the difference between charges and electron/proton ?
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voltage and current are the cornerstone concepts in electricity . we will create our first mental models for these basic electrical quantities . we will also talk about power , which is what happens when voltage and current act together . charge the concept of electricity arises from an observation of nature . we observe a force between objects , that , like gravity , acts at a distance . the source of this force has been given the name charge . a very noticeable thing about electric force is that it is large , far greater than the force of gravity . unlike gravity , however , there are two types of electric charge . opposite types of charge attract , and like types of charge repel . gravity has only one type : it only attracts , never repels . conductors and insulators conductors are made of atoms whose outer , or valence , electrons have relatively weak bonds to their nuclei , as shown in this fanciful image of a copper atom . when a bunch of metal atoms are together , they gladly share their outer electrons with each other , creating a `` swarm '' of electrons not associated with a particular nucleus . a very small electric force can make the electron swarm move . copper , gold , silver , and aluminum are good conductors . so is saltwater . there are also poor conductors . tungsten—a metal used for light bulb filaments—and carbon—used in graphite form in pencils—are relatively poor conductors because their electrons are less prone to move . insulators are materials whose outer electrons are tightly bound to their nuclei . modest electric forces are not able to pull these electrons free . when an electric force is applied , the electron clouds around the atom stretch and deform in response to the force , but the electrons do not depart . glass , plastic , stone , and air are insulators . even for insulators , though , electric force can always be turned up high enough to rip electrons away—this is called breakdown . that 's what is happening to air molecules when you see a spark . semiconductor materials fall between insulators and conductors . they usually act like insulators , but we can make them act like conductors under certain circumstances . the most well-known semiconductor material is silicon ( atomic number $ 14 $ ) . our ability to finely control the insulating and conducting properties of silicon allows us to create modern marvels like computers and mobile phones . the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current . current is reported as the number of charges per unit time passing through a boundary . visualize placing a boundary all the way through a wire . station yourself near the boundary and count the number of charges passing by . report how much charge passed through the boundary in one second . we assign a positive sign to current corresponding to the direction a positive charge would be moving . since current is the amount of charge passing through a boundary in a fixed amount of time , it can be expressed mathematically using the following equation : $ i = \dfrac { dq } { dt } $ that 's current in a nutshell . a few remarks on current what carries current in metal ? since electrons are free to move about in metals , moving electrons are what makes up the current in metals . the positive nuclei in metal atoms are fixed in place and do not contribute to current . even though electrons have a negative charge and do almost all the work in most electric circuits , we still define a positive current as the direction a positive charge would move . this is a very old historical convention . can current be carried by positive charges ? yes . there are lots of examples . current is carried by both positive and negative charges in saltwater : if we put ordinary table salt in water , it becomes a good conductor . table salt is sodium chloride , nacl . the salt dissolves in water , into free-floating na $ ^+ $ and cl $ ^- $ ions . both ions respond to electric force and move through the saltwater solution , in opposite directions . in this case , the current is composed of moving atoms , both positive and negative ions , not just loose electrons . inside our bodies , electrical currents are moving ions , both positive and negative . the same definition of current works : count the number of charges passing by in a fixed amount of time . what causes current ? charged objects move in response to electric and magnetic forces . these forces come from electric and magnetic fields , which in turn come from the position and motion of other charges . what is the speed of current ? we do n't talk very often about the speed of current . answering the question , `` how fast is the current flowing ? '' requires understanding of a complex physical phenomenon and is not often relevant . current usually is n't about meters per second , it 's about charge per second . more often , we answer the question `` how much current is flowing ? '' all the time . how do we talk about current ? when discussing current , terms like through and in make a lot of sense . current flows through a resistor ; current flows in a wire . if you hear , `` the current across ... '' , it should sound odd . voltage to get our initial toehold on the concept of voltage , let 's look at an analogy : voltage resembles gravity for a mass $ m $ , a change of height $ h $ corresponds to a change in potential energy , $ \delta u = mg\delta h $ . for a charged particle $ q $ , a voltage $ v $ corresponds to a change in potential energy , $ \delta u = qv $ . voltage in an electric circuit is analogous to the product of $ g\cdot \delta h $ . where $ g $ is the acceleration due to gravity and $ \delta h $ is the change of height . a ball at the top of the hill rolls down . when it is halfway down , it has given up half of its potential energy . an electron at the top of a voltage `` hill '' travels `` downhill '' through wires and elements of a circuit . it gives up its potential energy , doing work along the way . when the electron is halfway down the hill , it has given up , or `` dropped '' , half of its potential energy . for both the ball and the electron , the trip down the hill happens spontaneously . the ball and electron move towards a lower energy state all by themselves . on the trip down , there can be things in the way of the ball , like trees or bears to bounce off . for electrons , we can guide electrons using wires and make them flow through electronic components —circuit design— and do interesting things along the way . we can express the voltage between two points mathematically as the change of energy experienced by a charge : $ v = \dfrac { \delta u } { q } $ that 's an intuitive description of voltage in a nutshell . power power is defined as the rate energy ( $ \text u $ ) is transformed or transferred over time . we measure power in units of joules/second , also known as watts . ( $ 1 \ , \text { watt } = 1\ , \text { joule } /\text { second } $ ) $ \text { power } = \dfrac { \text du } { \text dt } $ an electric circuit is capable of transferring power . current is the rate of flow of charge , and voltage measures the energy transferred per unit of charge . we can insert these definitions into the equation for power : $ \text { power } = \dfrac { \text du } { \text dt } = \dfrac { \text du } { \text dq } \cdot \dfrac { \text dq } { \text dt } = v \ , i $ electrical power is the product of voltage times current . in units of watts . summary these mental models for current and voltage will get us started on all sorts of interesting electric circuits . if you want to reach beyond this intuitive description of voltage you can read this more formal mathematical description of electric potential and voltage .
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voltage and current are the cornerstone concepts in electricity . we will create our first mental models for these basic electrical quantities .
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if water is a poor conductor of electricity , why do we get electrocuted if we stand in water and electricity is introduced ?
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voltage and current are the cornerstone concepts in electricity . we will create our first mental models for these basic electrical quantities . we will also talk about power , which is what happens when voltage and current act together . charge the concept of electricity arises from an observation of nature . we observe a force between objects , that , like gravity , acts at a distance . the source of this force has been given the name charge . a very noticeable thing about electric force is that it is large , far greater than the force of gravity . unlike gravity , however , there are two types of electric charge . opposite types of charge attract , and like types of charge repel . gravity has only one type : it only attracts , never repels . conductors and insulators conductors are made of atoms whose outer , or valence , electrons have relatively weak bonds to their nuclei , as shown in this fanciful image of a copper atom . when a bunch of metal atoms are together , they gladly share their outer electrons with each other , creating a `` swarm '' of electrons not associated with a particular nucleus . a very small electric force can make the electron swarm move . copper , gold , silver , and aluminum are good conductors . so is saltwater . there are also poor conductors . tungsten—a metal used for light bulb filaments—and carbon—used in graphite form in pencils—are relatively poor conductors because their electrons are less prone to move . insulators are materials whose outer electrons are tightly bound to their nuclei . modest electric forces are not able to pull these electrons free . when an electric force is applied , the electron clouds around the atom stretch and deform in response to the force , but the electrons do not depart . glass , plastic , stone , and air are insulators . even for insulators , though , electric force can always be turned up high enough to rip electrons away—this is called breakdown . that 's what is happening to air molecules when you see a spark . semiconductor materials fall between insulators and conductors . they usually act like insulators , but we can make them act like conductors under certain circumstances . the most well-known semiconductor material is silicon ( atomic number $ 14 $ ) . our ability to finely control the insulating and conducting properties of silicon allows us to create modern marvels like computers and mobile phones . the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current . current is reported as the number of charges per unit time passing through a boundary . visualize placing a boundary all the way through a wire . station yourself near the boundary and count the number of charges passing by . report how much charge passed through the boundary in one second . we assign a positive sign to current corresponding to the direction a positive charge would be moving . since current is the amount of charge passing through a boundary in a fixed amount of time , it can be expressed mathematically using the following equation : $ i = \dfrac { dq } { dt } $ that 's current in a nutshell . a few remarks on current what carries current in metal ? since electrons are free to move about in metals , moving electrons are what makes up the current in metals . the positive nuclei in metal atoms are fixed in place and do not contribute to current . even though electrons have a negative charge and do almost all the work in most electric circuits , we still define a positive current as the direction a positive charge would move . this is a very old historical convention . can current be carried by positive charges ? yes . there are lots of examples . current is carried by both positive and negative charges in saltwater : if we put ordinary table salt in water , it becomes a good conductor . table salt is sodium chloride , nacl . the salt dissolves in water , into free-floating na $ ^+ $ and cl $ ^- $ ions . both ions respond to electric force and move through the saltwater solution , in opposite directions . in this case , the current is composed of moving atoms , both positive and negative ions , not just loose electrons . inside our bodies , electrical currents are moving ions , both positive and negative . the same definition of current works : count the number of charges passing by in a fixed amount of time . what causes current ? charged objects move in response to electric and magnetic forces . these forces come from electric and magnetic fields , which in turn come from the position and motion of other charges . what is the speed of current ? we do n't talk very often about the speed of current . answering the question , `` how fast is the current flowing ? '' requires understanding of a complex physical phenomenon and is not often relevant . current usually is n't about meters per second , it 's about charge per second . more often , we answer the question `` how much current is flowing ? '' all the time . how do we talk about current ? when discussing current , terms like through and in make a lot of sense . current flows through a resistor ; current flows in a wire . if you hear , `` the current across ... '' , it should sound odd . voltage to get our initial toehold on the concept of voltage , let 's look at an analogy : voltage resembles gravity for a mass $ m $ , a change of height $ h $ corresponds to a change in potential energy , $ \delta u = mg\delta h $ . for a charged particle $ q $ , a voltage $ v $ corresponds to a change in potential energy , $ \delta u = qv $ . voltage in an electric circuit is analogous to the product of $ g\cdot \delta h $ . where $ g $ is the acceleration due to gravity and $ \delta h $ is the change of height . a ball at the top of the hill rolls down . when it is halfway down , it has given up half of its potential energy . an electron at the top of a voltage `` hill '' travels `` downhill '' through wires and elements of a circuit . it gives up its potential energy , doing work along the way . when the electron is halfway down the hill , it has given up , or `` dropped '' , half of its potential energy . for both the ball and the electron , the trip down the hill happens spontaneously . the ball and electron move towards a lower energy state all by themselves . on the trip down , there can be things in the way of the ball , like trees or bears to bounce off . for electrons , we can guide electrons using wires and make them flow through electronic components —circuit design— and do interesting things along the way . we can express the voltage between two points mathematically as the change of energy experienced by a charge : $ v = \dfrac { \delta u } { q } $ that 's an intuitive description of voltage in a nutshell . power power is defined as the rate energy ( $ \text u $ ) is transformed or transferred over time . we measure power in units of joules/second , also known as watts . ( $ 1 \ , \text { watt } = 1\ , \text { joule } /\text { second } $ ) $ \text { power } = \dfrac { \text du } { \text dt } $ an electric circuit is capable of transferring power . current is the rate of flow of charge , and voltage measures the energy transferred per unit of charge . we can insert these definitions into the equation for power : $ \text { power } = \dfrac { \text du } { \text dt } = \dfrac { \text du } { \text dq } \cdot \dfrac { \text dq } { \text dt } = v \ , i $ electrical power is the product of voltage times current . in units of watts . summary these mental models for current and voltage will get us started on all sorts of interesting electric circuits . if you want to reach beyond this intuitive description of voltage you can read this more formal mathematical description of electric potential and voltage .
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the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current .
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why is i the symbol for current ?
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voltage and current are the cornerstone concepts in electricity . we will create our first mental models for these basic electrical quantities . we will also talk about power , which is what happens when voltage and current act together . charge the concept of electricity arises from an observation of nature . we observe a force between objects , that , like gravity , acts at a distance . the source of this force has been given the name charge . a very noticeable thing about electric force is that it is large , far greater than the force of gravity . unlike gravity , however , there are two types of electric charge . opposite types of charge attract , and like types of charge repel . gravity has only one type : it only attracts , never repels . conductors and insulators conductors are made of atoms whose outer , or valence , electrons have relatively weak bonds to their nuclei , as shown in this fanciful image of a copper atom . when a bunch of metal atoms are together , they gladly share their outer electrons with each other , creating a `` swarm '' of electrons not associated with a particular nucleus . a very small electric force can make the electron swarm move . copper , gold , silver , and aluminum are good conductors . so is saltwater . there are also poor conductors . tungsten—a metal used for light bulb filaments—and carbon—used in graphite form in pencils—are relatively poor conductors because their electrons are less prone to move . insulators are materials whose outer electrons are tightly bound to their nuclei . modest electric forces are not able to pull these electrons free . when an electric force is applied , the electron clouds around the atom stretch and deform in response to the force , but the electrons do not depart . glass , plastic , stone , and air are insulators . even for insulators , though , electric force can always be turned up high enough to rip electrons away—this is called breakdown . that 's what is happening to air molecules when you see a spark . semiconductor materials fall between insulators and conductors . they usually act like insulators , but we can make them act like conductors under certain circumstances . the most well-known semiconductor material is silicon ( atomic number $ 14 $ ) . our ability to finely control the insulating and conducting properties of silicon allows us to create modern marvels like computers and mobile phones . the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current . current is reported as the number of charges per unit time passing through a boundary . visualize placing a boundary all the way through a wire . station yourself near the boundary and count the number of charges passing by . report how much charge passed through the boundary in one second . we assign a positive sign to current corresponding to the direction a positive charge would be moving . since current is the amount of charge passing through a boundary in a fixed amount of time , it can be expressed mathematically using the following equation : $ i = \dfrac { dq } { dt } $ that 's current in a nutshell . a few remarks on current what carries current in metal ? since electrons are free to move about in metals , moving electrons are what makes up the current in metals . the positive nuclei in metal atoms are fixed in place and do not contribute to current . even though electrons have a negative charge and do almost all the work in most electric circuits , we still define a positive current as the direction a positive charge would move . this is a very old historical convention . can current be carried by positive charges ? yes . there are lots of examples . current is carried by both positive and negative charges in saltwater : if we put ordinary table salt in water , it becomes a good conductor . table salt is sodium chloride , nacl . the salt dissolves in water , into free-floating na $ ^+ $ and cl $ ^- $ ions . both ions respond to electric force and move through the saltwater solution , in opposite directions . in this case , the current is composed of moving atoms , both positive and negative ions , not just loose electrons . inside our bodies , electrical currents are moving ions , both positive and negative . the same definition of current works : count the number of charges passing by in a fixed amount of time . what causes current ? charged objects move in response to electric and magnetic forces . these forces come from electric and magnetic fields , which in turn come from the position and motion of other charges . what is the speed of current ? we do n't talk very often about the speed of current . answering the question , `` how fast is the current flowing ? '' requires understanding of a complex physical phenomenon and is not often relevant . current usually is n't about meters per second , it 's about charge per second . more often , we answer the question `` how much current is flowing ? '' all the time . how do we talk about current ? when discussing current , terms like through and in make a lot of sense . current flows through a resistor ; current flows in a wire . if you hear , `` the current across ... '' , it should sound odd . voltage to get our initial toehold on the concept of voltage , let 's look at an analogy : voltage resembles gravity for a mass $ m $ , a change of height $ h $ corresponds to a change in potential energy , $ \delta u = mg\delta h $ . for a charged particle $ q $ , a voltage $ v $ corresponds to a change in potential energy , $ \delta u = qv $ . voltage in an electric circuit is analogous to the product of $ g\cdot \delta h $ . where $ g $ is the acceleration due to gravity and $ \delta h $ is the change of height . a ball at the top of the hill rolls down . when it is halfway down , it has given up half of its potential energy . an electron at the top of a voltage `` hill '' travels `` downhill '' through wires and elements of a circuit . it gives up its potential energy , doing work along the way . when the electron is halfway down the hill , it has given up , or `` dropped '' , half of its potential energy . for both the ball and the electron , the trip down the hill happens spontaneously . the ball and electron move towards a lower energy state all by themselves . on the trip down , there can be things in the way of the ball , like trees or bears to bounce off . for electrons , we can guide electrons using wires and make them flow through electronic components —circuit design— and do interesting things along the way . we can express the voltage between two points mathematically as the change of energy experienced by a charge : $ v = \dfrac { \delta u } { q } $ that 's an intuitive description of voltage in a nutshell . power power is defined as the rate energy ( $ \text u $ ) is transformed or transferred over time . we measure power in units of joules/second , also known as watts . ( $ 1 \ , \text { watt } = 1\ , \text { joule } /\text { second } $ ) $ \text { power } = \dfrac { \text du } { \text dt } $ an electric circuit is capable of transferring power . current is the rate of flow of charge , and voltage measures the energy transferred per unit of charge . we can insert these definitions into the equation for power : $ \text { power } = \dfrac { \text du } { \text dt } = \dfrac { \text du } { \text dq } \cdot \dfrac { \text dq } { \text dt } = v \ , i $ electrical power is the product of voltage times current . in units of watts . summary these mental models for current and voltage will get us started on all sorts of interesting electric circuits . if you want to reach beyond this intuitive description of voltage you can read this more formal mathematical description of electric potential and voltage .
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the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current .
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are current and amps the same thing ?
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voltage and current are the cornerstone concepts in electricity . we will create our first mental models for these basic electrical quantities . we will also talk about power , which is what happens when voltage and current act together . charge the concept of electricity arises from an observation of nature . we observe a force between objects , that , like gravity , acts at a distance . the source of this force has been given the name charge . a very noticeable thing about electric force is that it is large , far greater than the force of gravity . unlike gravity , however , there are two types of electric charge . opposite types of charge attract , and like types of charge repel . gravity has only one type : it only attracts , never repels . conductors and insulators conductors are made of atoms whose outer , or valence , electrons have relatively weak bonds to their nuclei , as shown in this fanciful image of a copper atom . when a bunch of metal atoms are together , they gladly share their outer electrons with each other , creating a `` swarm '' of electrons not associated with a particular nucleus . a very small electric force can make the electron swarm move . copper , gold , silver , and aluminum are good conductors . so is saltwater . there are also poor conductors . tungsten—a metal used for light bulb filaments—and carbon—used in graphite form in pencils—are relatively poor conductors because their electrons are less prone to move . insulators are materials whose outer electrons are tightly bound to their nuclei . modest electric forces are not able to pull these electrons free . when an electric force is applied , the electron clouds around the atom stretch and deform in response to the force , but the electrons do not depart . glass , plastic , stone , and air are insulators . even for insulators , though , electric force can always be turned up high enough to rip electrons away—this is called breakdown . that 's what is happening to air molecules when you see a spark . semiconductor materials fall between insulators and conductors . they usually act like insulators , but we can make them act like conductors under certain circumstances . the most well-known semiconductor material is silicon ( atomic number $ 14 $ ) . our ability to finely control the insulating and conducting properties of silicon allows us to create modern marvels like computers and mobile phones . the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current . current is reported as the number of charges per unit time passing through a boundary . visualize placing a boundary all the way through a wire . station yourself near the boundary and count the number of charges passing by . report how much charge passed through the boundary in one second . we assign a positive sign to current corresponding to the direction a positive charge would be moving . since current is the amount of charge passing through a boundary in a fixed amount of time , it can be expressed mathematically using the following equation : $ i = \dfrac { dq } { dt } $ that 's current in a nutshell . a few remarks on current what carries current in metal ? since electrons are free to move about in metals , moving electrons are what makes up the current in metals . the positive nuclei in metal atoms are fixed in place and do not contribute to current . even though electrons have a negative charge and do almost all the work in most electric circuits , we still define a positive current as the direction a positive charge would move . this is a very old historical convention . can current be carried by positive charges ? yes . there are lots of examples . current is carried by both positive and negative charges in saltwater : if we put ordinary table salt in water , it becomes a good conductor . table salt is sodium chloride , nacl . the salt dissolves in water , into free-floating na $ ^+ $ and cl $ ^- $ ions . both ions respond to electric force and move through the saltwater solution , in opposite directions . in this case , the current is composed of moving atoms , both positive and negative ions , not just loose electrons . inside our bodies , electrical currents are moving ions , both positive and negative . the same definition of current works : count the number of charges passing by in a fixed amount of time . what causes current ? charged objects move in response to electric and magnetic forces . these forces come from electric and magnetic fields , which in turn come from the position and motion of other charges . what is the speed of current ? we do n't talk very often about the speed of current . answering the question , `` how fast is the current flowing ? '' requires understanding of a complex physical phenomenon and is not often relevant . current usually is n't about meters per second , it 's about charge per second . more often , we answer the question `` how much current is flowing ? '' all the time . how do we talk about current ? when discussing current , terms like through and in make a lot of sense . current flows through a resistor ; current flows in a wire . if you hear , `` the current across ... '' , it should sound odd . voltage to get our initial toehold on the concept of voltage , let 's look at an analogy : voltage resembles gravity for a mass $ m $ , a change of height $ h $ corresponds to a change in potential energy , $ \delta u = mg\delta h $ . for a charged particle $ q $ , a voltage $ v $ corresponds to a change in potential energy , $ \delta u = qv $ . voltage in an electric circuit is analogous to the product of $ g\cdot \delta h $ . where $ g $ is the acceleration due to gravity and $ \delta h $ is the change of height . a ball at the top of the hill rolls down . when it is halfway down , it has given up half of its potential energy . an electron at the top of a voltage `` hill '' travels `` downhill '' through wires and elements of a circuit . it gives up its potential energy , doing work along the way . when the electron is halfway down the hill , it has given up , or `` dropped '' , half of its potential energy . for both the ball and the electron , the trip down the hill happens spontaneously . the ball and electron move towards a lower energy state all by themselves . on the trip down , there can be things in the way of the ball , like trees or bears to bounce off . for electrons , we can guide electrons using wires and make them flow through electronic components —circuit design— and do interesting things along the way . we can express the voltage between two points mathematically as the change of energy experienced by a charge : $ v = \dfrac { \delta u } { q } $ that 's an intuitive description of voltage in a nutshell . power power is defined as the rate energy ( $ \text u $ ) is transformed or transferred over time . we measure power in units of joules/second , also known as watts . ( $ 1 \ , \text { watt } = 1\ , \text { joule } /\text { second } $ ) $ \text { power } = \dfrac { \text du } { \text dt } $ an electric circuit is capable of transferring power . current is the rate of flow of charge , and voltage measures the energy transferred per unit of charge . we can insert these definitions into the equation for power : $ \text { power } = \dfrac { \text du } { \text dt } = \dfrac { \text du } { \text dq } \cdot \dfrac { \text dq } { \text dt } = v \ , i $ electrical power is the product of voltage times current . in units of watts . summary these mental models for current and voltage will get us started on all sorts of interesting electric circuits . if you want to reach beyond this intuitive description of voltage you can read this more formal mathematical description of electric potential and voltage .
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the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current .
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is amperage the measure of current ?
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voltage and current are the cornerstone concepts in electricity . we will create our first mental models for these basic electrical quantities . we will also talk about power , which is what happens when voltage and current act together . charge the concept of electricity arises from an observation of nature . we observe a force between objects , that , like gravity , acts at a distance . the source of this force has been given the name charge . a very noticeable thing about electric force is that it is large , far greater than the force of gravity . unlike gravity , however , there are two types of electric charge . opposite types of charge attract , and like types of charge repel . gravity has only one type : it only attracts , never repels . conductors and insulators conductors are made of atoms whose outer , or valence , electrons have relatively weak bonds to their nuclei , as shown in this fanciful image of a copper atom . when a bunch of metal atoms are together , they gladly share their outer electrons with each other , creating a `` swarm '' of electrons not associated with a particular nucleus . a very small electric force can make the electron swarm move . copper , gold , silver , and aluminum are good conductors . so is saltwater . there are also poor conductors . tungsten—a metal used for light bulb filaments—and carbon—used in graphite form in pencils—are relatively poor conductors because their electrons are less prone to move . insulators are materials whose outer electrons are tightly bound to their nuclei . modest electric forces are not able to pull these electrons free . when an electric force is applied , the electron clouds around the atom stretch and deform in response to the force , but the electrons do not depart . glass , plastic , stone , and air are insulators . even for insulators , though , electric force can always be turned up high enough to rip electrons away—this is called breakdown . that 's what is happening to air molecules when you see a spark . semiconductor materials fall between insulators and conductors . they usually act like insulators , but we can make them act like conductors under certain circumstances . the most well-known semiconductor material is silicon ( atomic number $ 14 $ ) . our ability to finely control the insulating and conducting properties of silicon allows us to create modern marvels like computers and mobile phones . the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current . current is reported as the number of charges per unit time passing through a boundary . visualize placing a boundary all the way through a wire . station yourself near the boundary and count the number of charges passing by . report how much charge passed through the boundary in one second . we assign a positive sign to current corresponding to the direction a positive charge would be moving . since current is the amount of charge passing through a boundary in a fixed amount of time , it can be expressed mathematically using the following equation : $ i = \dfrac { dq } { dt } $ that 's current in a nutshell . a few remarks on current what carries current in metal ? since electrons are free to move about in metals , moving electrons are what makes up the current in metals . the positive nuclei in metal atoms are fixed in place and do not contribute to current . even though electrons have a negative charge and do almost all the work in most electric circuits , we still define a positive current as the direction a positive charge would move . this is a very old historical convention . can current be carried by positive charges ? yes . there are lots of examples . current is carried by both positive and negative charges in saltwater : if we put ordinary table salt in water , it becomes a good conductor . table salt is sodium chloride , nacl . the salt dissolves in water , into free-floating na $ ^+ $ and cl $ ^- $ ions . both ions respond to electric force and move through the saltwater solution , in opposite directions . in this case , the current is composed of moving atoms , both positive and negative ions , not just loose electrons . inside our bodies , electrical currents are moving ions , both positive and negative . the same definition of current works : count the number of charges passing by in a fixed amount of time . what causes current ? charged objects move in response to electric and magnetic forces . these forces come from electric and magnetic fields , which in turn come from the position and motion of other charges . what is the speed of current ? we do n't talk very often about the speed of current . answering the question , `` how fast is the current flowing ? '' requires understanding of a complex physical phenomenon and is not often relevant . current usually is n't about meters per second , it 's about charge per second . more often , we answer the question `` how much current is flowing ? '' all the time . how do we talk about current ? when discussing current , terms like through and in make a lot of sense . current flows through a resistor ; current flows in a wire . if you hear , `` the current across ... '' , it should sound odd . voltage to get our initial toehold on the concept of voltage , let 's look at an analogy : voltage resembles gravity for a mass $ m $ , a change of height $ h $ corresponds to a change in potential energy , $ \delta u = mg\delta h $ . for a charged particle $ q $ , a voltage $ v $ corresponds to a change in potential energy , $ \delta u = qv $ . voltage in an electric circuit is analogous to the product of $ g\cdot \delta h $ . where $ g $ is the acceleration due to gravity and $ \delta h $ is the change of height . a ball at the top of the hill rolls down . when it is halfway down , it has given up half of its potential energy . an electron at the top of a voltage `` hill '' travels `` downhill '' through wires and elements of a circuit . it gives up its potential energy , doing work along the way . when the electron is halfway down the hill , it has given up , or `` dropped '' , half of its potential energy . for both the ball and the electron , the trip down the hill happens spontaneously . the ball and electron move towards a lower energy state all by themselves . on the trip down , there can be things in the way of the ball , like trees or bears to bounce off . for electrons , we can guide electrons using wires and make them flow through electronic components —circuit design— and do interesting things along the way . we can express the voltage between two points mathematically as the change of energy experienced by a charge : $ v = \dfrac { \delta u } { q } $ that 's an intuitive description of voltage in a nutshell . power power is defined as the rate energy ( $ \text u $ ) is transformed or transferred over time . we measure power in units of joules/second , also known as watts . ( $ 1 \ , \text { watt } = 1\ , \text { joule } /\text { second } $ ) $ \text { power } = \dfrac { \text du } { \text dt } $ an electric circuit is capable of transferring power . current is the rate of flow of charge , and voltage measures the energy transferred per unit of charge . we can insert these definitions into the equation for power : $ \text { power } = \dfrac { \text du } { \text dt } = \dfrac { \text du } { \text dq } \cdot \dfrac { \text dq } { \text dt } = v \ , i $ electrical power is the product of voltage times current . in units of watts . summary these mental models for current and voltage will get us started on all sorts of interesting electric circuits . if you want to reach beyond this intuitive description of voltage you can read this more formal mathematical description of electric potential and voltage .
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for both the ball and the electron , the trip down the hill happens spontaneously . the ball and electron move towards a lower energy state all by themselves . on the trip down , there can be things in the way of the ball , like trees or bears to bounce off .
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i am still confused about voltage , i ca n't understand why the eletron moves towards a lower energy state ?
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voltage and current are the cornerstone concepts in electricity . we will create our first mental models for these basic electrical quantities . we will also talk about power , which is what happens when voltage and current act together . charge the concept of electricity arises from an observation of nature . we observe a force between objects , that , like gravity , acts at a distance . the source of this force has been given the name charge . a very noticeable thing about electric force is that it is large , far greater than the force of gravity . unlike gravity , however , there are two types of electric charge . opposite types of charge attract , and like types of charge repel . gravity has only one type : it only attracts , never repels . conductors and insulators conductors are made of atoms whose outer , or valence , electrons have relatively weak bonds to their nuclei , as shown in this fanciful image of a copper atom . when a bunch of metal atoms are together , they gladly share their outer electrons with each other , creating a `` swarm '' of electrons not associated with a particular nucleus . a very small electric force can make the electron swarm move . copper , gold , silver , and aluminum are good conductors . so is saltwater . there are also poor conductors . tungsten—a metal used for light bulb filaments—and carbon—used in graphite form in pencils—are relatively poor conductors because their electrons are less prone to move . insulators are materials whose outer electrons are tightly bound to their nuclei . modest electric forces are not able to pull these electrons free . when an electric force is applied , the electron clouds around the atom stretch and deform in response to the force , but the electrons do not depart . glass , plastic , stone , and air are insulators . even for insulators , though , electric force can always be turned up high enough to rip electrons away—this is called breakdown . that 's what is happening to air molecules when you see a spark . semiconductor materials fall between insulators and conductors . they usually act like insulators , but we can make them act like conductors under certain circumstances . the most well-known semiconductor material is silicon ( atomic number $ 14 $ ) . our ability to finely control the insulating and conducting properties of silicon allows us to create modern marvels like computers and mobile phones . the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current . current is reported as the number of charges per unit time passing through a boundary . visualize placing a boundary all the way through a wire . station yourself near the boundary and count the number of charges passing by . report how much charge passed through the boundary in one second . we assign a positive sign to current corresponding to the direction a positive charge would be moving . since current is the amount of charge passing through a boundary in a fixed amount of time , it can be expressed mathematically using the following equation : $ i = \dfrac { dq } { dt } $ that 's current in a nutshell . a few remarks on current what carries current in metal ? since electrons are free to move about in metals , moving electrons are what makes up the current in metals . the positive nuclei in metal atoms are fixed in place and do not contribute to current . even though electrons have a negative charge and do almost all the work in most electric circuits , we still define a positive current as the direction a positive charge would move . this is a very old historical convention . can current be carried by positive charges ? yes . there are lots of examples . current is carried by both positive and negative charges in saltwater : if we put ordinary table salt in water , it becomes a good conductor . table salt is sodium chloride , nacl . the salt dissolves in water , into free-floating na $ ^+ $ and cl $ ^- $ ions . both ions respond to electric force and move through the saltwater solution , in opposite directions . in this case , the current is composed of moving atoms , both positive and negative ions , not just loose electrons . inside our bodies , electrical currents are moving ions , both positive and negative . the same definition of current works : count the number of charges passing by in a fixed amount of time . what causes current ? charged objects move in response to electric and magnetic forces . these forces come from electric and magnetic fields , which in turn come from the position and motion of other charges . what is the speed of current ? we do n't talk very often about the speed of current . answering the question , `` how fast is the current flowing ? '' requires understanding of a complex physical phenomenon and is not often relevant . current usually is n't about meters per second , it 's about charge per second . more often , we answer the question `` how much current is flowing ? '' all the time . how do we talk about current ? when discussing current , terms like through and in make a lot of sense . current flows through a resistor ; current flows in a wire . if you hear , `` the current across ... '' , it should sound odd . voltage to get our initial toehold on the concept of voltage , let 's look at an analogy : voltage resembles gravity for a mass $ m $ , a change of height $ h $ corresponds to a change in potential energy , $ \delta u = mg\delta h $ . for a charged particle $ q $ , a voltage $ v $ corresponds to a change in potential energy , $ \delta u = qv $ . voltage in an electric circuit is analogous to the product of $ g\cdot \delta h $ . where $ g $ is the acceleration due to gravity and $ \delta h $ is the change of height . a ball at the top of the hill rolls down . when it is halfway down , it has given up half of its potential energy . an electron at the top of a voltage `` hill '' travels `` downhill '' through wires and elements of a circuit . it gives up its potential energy , doing work along the way . when the electron is halfway down the hill , it has given up , or `` dropped '' , half of its potential energy . for both the ball and the electron , the trip down the hill happens spontaneously . the ball and electron move towards a lower energy state all by themselves . on the trip down , there can be things in the way of the ball , like trees or bears to bounce off . for electrons , we can guide electrons using wires and make them flow through electronic components —circuit design— and do interesting things along the way . we can express the voltage between two points mathematically as the change of energy experienced by a charge : $ v = \dfrac { \delta u } { q } $ that 's an intuitive description of voltage in a nutshell . power power is defined as the rate energy ( $ \text u $ ) is transformed or transferred over time . we measure power in units of joules/second , also known as watts . ( $ 1 \ , \text { watt } = 1\ , \text { joule } /\text { second } $ ) $ \text { power } = \dfrac { \text du } { \text dt } $ an electric circuit is capable of transferring power . current is the rate of flow of charge , and voltage measures the energy transferred per unit of charge . we can insert these definitions into the equation for power : $ \text { power } = \dfrac { \text du } { \text dt } = \dfrac { \text du } { \text dq } \cdot \dfrac { \text dq } { \text dt } = v \ , i $ electrical power is the product of voltage times current . in units of watts . summary these mental models for current and voltage will get us started on all sorts of interesting electric circuits . if you want to reach beyond this intuitive description of voltage you can read this more formal mathematical description of electric potential and voltage .
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the source of this force has been given the name charge . a very noticeable thing about electric force is that it is large , far greater than the force of gravity . unlike gravity , however , there are two types of electric charge .
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is electric force a vector quantity or a scalar quantity ?
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voltage and current are the cornerstone concepts in electricity . we will create our first mental models for these basic electrical quantities . we will also talk about power , which is what happens when voltage and current act together . charge the concept of electricity arises from an observation of nature . we observe a force between objects , that , like gravity , acts at a distance . the source of this force has been given the name charge . a very noticeable thing about electric force is that it is large , far greater than the force of gravity . unlike gravity , however , there are two types of electric charge . opposite types of charge attract , and like types of charge repel . gravity has only one type : it only attracts , never repels . conductors and insulators conductors are made of atoms whose outer , or valence , electrons have relatively weak bonds to their nuclei , as shown in this fanciful image of a copper atom . when a bunch of metal atoms are together , they gladly share their outer electrons with each other , creating a `` swarm '' of electrons not associated with a particular nucleus . a very small electric force can make the electron swarm move . copper , gold , silver , and aluminum are good conductors . so is saltwater . there are also poor conductors . tungsten—a metal used for light bulb filaments—and carbon—used in graphite form in pencils—are relatively poor conductors because their electrons are less prone to move . insulators are materials whose outer electrons are tightly bound to their nuclei . modest electric forces are not able to pull these electrons free . when an electric force is applied , the electron clouds around the atom stretch and deform in response to the force , but the electrons do not depart . glass , plastic , stone , and air are insulators . even for insulators , though , electric force can always be turned up high enough to rip electrons away—this is called breakdown . that 's what is happening to air molecules when you see a spark . semiconductor materials fall between insulators and conductors . they usually act like insulators , but we can make them act like conductors under certain circumstances . the most well-known semiconductor material is silicon ( atomic number $ 14 $ ) . our ability to finely control the insulating and conducting properties of silicon allows us to create modern marvels like computers and mobile phones . the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current . current is reported as the number of charges per unit time passing through a boundary . visualize placing a boundary all the way through a wire . station yourself near the boundary and count the number of charges passing by . report how much charge passed through the boundary in one second . we assign a positive sign to current corresponding to the direction a positive charge would be moving . since current is the amount of charge passing through a boundary in a fixed amount of time , it can be expressed mathematically using the following equation : $ i = \dfrac { dq } { dt } $ that 's current in a nutshell . a few remarks on current what carries current in metal ? since electrons are free to move about in metals , moving electrons are what makes up the current in metals . the positive nuclei in metal atoms are fixed in place and do not contribute to current . even though electrons have a negative charge and do almost all the work in most electric circuits , we still define a positive current as the direction a positive charge would move . this is a very old historical convention . can current be carried by positive charges ? yes . there are lots of examples . current is carried by both positive and negative charges in saltwater : if we put ordinary table salt in water , it becomes a good conductor . table salt is sodium chloride , nacl . the salt dissolves in water , into free-floating na $ ^+ $ and cl $ ^- $ ions . both ions respond to electric force and move through the saltwater solution , in opposite directions . in this case , the current is composed of moving atoms , both positive and negative ions , not just loose electrons . inside our bodies , electrical currents are moving ions , both positive and negative . the same definition of current works : count the number of charges passing by in a fixed amount of time . what causes current ? charged objects move in response to electric and magnetic forces . these forces come from electric and magnetic fields , which in turn come from the position and motion of other charges . what is the speed of current ? we do n't talk very often about the speed of current . answering the question , `` how fast is the current flowing ? '' requires understanding of a complex physical phenomenon and is not often relevant . current usually is n't about meters per second , it 's about charge per second . more often , we answer the question `` how much current is flowing ? '' all the time . how do we talk about current ? when discussing current , terms like through and in make a lot of sense . current flows through a resistor ; current flows in a wire . if you hear , `` the current across ... '' , it should sound odd . voltage to get our initial toehold on the concept of voltage , let 's look at an analogy : voltage resembles gravity for a mass $ m $ , a change of height $ h $ corresponds to a change in potential energy , $ \delta u = mg\delta h $ . for a charged particle $ q $ , a voltage $ v $ corresponds to a change in potential energy , $ \delta u = qv $ . voltage in an electric circuit is analogous to the product of $ g\cdot \delta h $ . where $ g $ is the acceleration due to gravity and $ \delta h $ is the change of height . a ball at the top of the hill rolls down . when it is halfway down , it has given up half of its potential energy . an electron at the top of a voltage `` hill '' travels `` downhill '' through wires and elements of a circuit . it gives up its potential energy , doing work along the way . when the electron is halfway down the hill , it has given up , or `` dropped '' , half of its potential energy . for both the ball and the electron , the trip down the hill happens spontaneously . the ball and electron move towards a lower energy state all by themselves . on the trip down , there can be things in the way of the ball , like trees or bears to bounce off . for electrons , we can guide electrons using wires and make them flow through electronic components —circuit design— and do interesting things along the way . we can express the voltage between two points mathematically as the change of energy experienced by a charge : $ v = \dfrac { \delta u } { q } $ that 's an intuitive description of voltage in a nutshell . power power is defined as the rate energy ( $ \text u $ ) is transformed or transferred over time . we measure power in units of joules/second , also known as watts . ( $ 1 \ , \text { watt } = 1\ , \text { joule } /\text { second } $ ) $ \text { power } = \dfrac { \text du } { \text dt } $ an electric circuit is capable of transferring power . current is the rate of flow of charge , and voltage measures the energy transferred per unit of charge . we can insert these definitions into the equation for power : $ \text { power } = \dfrac { \text du } { \text dt } = \dfrac { \text du } { \text dq } \cdot \dfrac { \text dq } { \text dt } = v \ , i $ electrical power is the product of voltage times current . in units of watts . summary these mental models for current and voltage will get us started on all sorts of interesting electric circuits . if you want to reach beyond this intuitive description of voltage you can read this more formal mathematical description of electric potential and voltage .
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unlike gravity , however , there are two types of electric charge . opposite types of charge attract , and like types of charge repel . gravity has only one type : it only attracts , never repels .
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if like charges repel , why do n't the electrons flowing around a circuit repel each other and flow in opposite directions ?
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voltage and current are the cornerstone concepts in electricity . we will create our first mental models for these basic electrical quantities . we will also talk about power , which is what happens when voltage and current act together . charge the concept of electricity arises from an observation of nature . we observe a force between objects , that , like gravity , acts at a distance . the source of this force has been given the name charge . a very noticeable thing about electric force is that it is large , far greater than the force of gravity . unlike gravity , however , there are two types of electric charge . opposite types of charge attract , and like types of charge repel . gravity has only one type : it only attracts , never repels . conductors and insulators conductors are made of atoms whose outer , or valence , electrons have relatively weak bonds to their nuclei , as shown in this fanciful image of a copper atom . when a bunch of metal atoms are together , they gladly share their outer electrons with each other , creating a `` swarm '' of electrons not associated with a particular nucleus . a very small electric force can make the electron swarm move . copper , gold , silver , and aluminum are good conductors . so is saltwater . there are also poor conductors . tungsten—a metal used for light bulb filaments—and carbon—used in graphite form in pencils—are relatively poor conductors because their electrons are less prone to move . insulators are materials whose outer electrons are tightly bound to their nuclei . modest electric forces are not able to pull these electrons free . when an electric force is applied , the electron clouds around the atom stretch and deform in response to the force , but the electrons do not depart . glass , plastic , stone , and air are insulators . even for insulators , though , electric force can always be turned up high enough to rip electrons away—this is called breakdown . that 's what is happening to air molecules when you see a spark . semiconductor materials fall between insulators and conductors . they usually act like insulators , but we can make them act like conductors under certain circumstances . the most well-known semiconductor material is silicon ( atomic number $ 14 $ ) . our ability to finely control the insulating and conducting properties of silicon allows us to create modern marvels like computers and mobile phones . the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current . current is reported as the number of charges per unit time passing through a boundary . visualize placing a boundary all the way through a wire . station yourself near the boundary and count the number of charges passing by . report how much charge passed through the boundary in one second . we assign a positive sign to current corresponding to the direction a positive charge would be moving . since current is the amount of charge passing through a boundary in a fixed amount of time , it can be expressed mathematically using the following equation : $ i = \dfrac { dq } { dt } $ that 's current in a nutshell . a few remarks on current what carries current in metal ? since electrons are free to move about in metals , moving electrons are what makes up the current in metals . the positive nuclei in metal atoms are fixed in place and do not contribute to current . even though electrons have a negative charge and do almost all the work in most electric circuits , we still define a positive current as the direction a positive charge would move . this is a very old historical convention . can current be carried by positive charges ? yes . there are lots of examples . current is carried by both positive and negative charges in saltwater : if we put ordinary table salt in water , it becomes a good conductor . table salt is sodium chloride , nacl . the salt dissolves in water , into free-floating na $ ^+ $ and cl $ ^- $ ions . both ions respond to electric force and move through the saltwater solution , in opposite directions . in this case , the current is composed of moving atoms , both positive and negative ions , not just loose electrons . inside our bodies , electrical currents are moving ions , both positive and negative . the same definition of current works : count the number of charges passing by in a fixed amount of time . what causes current ? charged objects move in response to electric and magnetic forces . these forces come from electric and magnetic fields , which in turn come from the position and motion of other charges . what is the speed of current ? we do n't talk very often about the speed of current . answering the question , `` how fast is the current flowing ? '' requires understanding of a complex physical phenomenon and is not often relevant . current usually is n't about meters per second , it 's about charge per second . more often , we answer the question `` how much current is flowing ? '' all the time . how do we talk about current ? when discussing current , terms like through and in make a lot of sense . current flows through a resistor ; current flows in a wire . if you hear , `` the current across ... '' , it should sound odd . voltage to get our initial toehold on the concept of voltage , let 's look at an analogy : voltage resembles gravity for a mass $ m $ , a change of height $ h $ corresponds to a change in potential energy , $ \delta u = mg\delta h $ . for a charged particle $ q $ , a voltage $ v $ corresponds to a change in potential energy , $ \delta u = qv $ . voltage in an electric circuit is analogous to the product of $ g\cdot \delta h $ . where $ g $ is the acceleration due to gravity and $ \delta h $ is the change of height . a ball at the top of the hill rolls down . when it is halfway down , it has given up half of its potential energy . an electron at the top of a voltage `` hill '' travels `` downhill '' through wires and elements of a circuit . it gives up its potential energy , doing work along the way . when the electron is halfway down the hill , it has given up , or `` dropped '' , half of its potential energy . for both the ball and the electron , the trip down the hill happens spontaneously . the ball and electron move towards a lower energy state all by themselves . on the trip down , there can be things in the way of the ball , like trees or bears to bounce off . for electrons , we can guide electrons using wires and make them flow through electronic components —circuit design— and do interesting things along the way . we can express the voltage between two points mathematically as the change of energy experienced by a charge : $ v = \dfrac { \delta u } { q } $ that 's an intuitive description of voltage in a nutshell . power power is defined as the rate energy ( $ \text u $ ) is transformed or transferred over time . we measure power in units of joules/second , also known as watts . ( $ 1 \ , \text { watt } = 1\ , \text { joule } /\text { second } $ ) $ \text { power } = \dfrac { \text du } { \text dt } $ an electric circuit is capable of transferring power . current is the rate of flow of charge , and voltage measures the energy transferred per unit of charge . we can insert these definitions into the equation for power : $ \text { power } = \dfrac { \text du } { \text dt } = \dfrac { \text du } { \text dq } \cdot \dfrac { \text dq } { \text dt } = v \ , i $ electrical power is the product of voltage times current . in units of watts . summary these mental models for current and voltage will get us started on all sorts of interesting electric circuits . if you want to reach beyond this intuitive description of voltage you can read this more formal mathematical description of electric potential and voltage .
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we can insert these definitions into the equation for power : $ \text { power } = \dfrac { \text du } { \text dt } = \dfrac { \text du } { \text dq } \cdot \dfrac { \text dq } { \text dt } = v \ , i $ electrical power is the product of voltage times current . in units of watts . summary these mental models for current and voltage will get us started on all sorts of interesting electric circuits .
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what is 960 watts in coulombs ?
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voltage and current are the cornerstone concepts in electricity . we will create our first mental models for these basic electrical quantities . we will also talk about power , which is what happens when voltage and current act together . charge the concept of electricity arises from an observation of nature . we observe a force between objects , that , like gravity , acts at a distance . the source of this force has been given the name charge . a very noticeable thing about electric force is that it is large , far greater than the force of gravity . unlike gravity , however , there are two types of electric charge . opposite types of charge attract , and like types of charge repel . gravity has only one type : it only attracts , never repels . conductors and insulators conductors are made of atoms whose outer , or valence , electrons have relatively weak bonds to their nuclei , as shown in this fanciful image of a copper atom . when a bunch of metal atoms are together , they gladly share their outer electrons with each other , creating a `` swarm '' of electrons not associated with a particular nucleus . a very small electric force can make the electron swarm move . copper , gold , silver , and aluminum are good conductors . so is saltwater . there are also poor conductors . tungsten—a metal used for light bulb filaments—and carbon—used in graphite form in pencils—are relatively poor conductors because their electrons are less prone to move . insulators are materials whose outer electrons are tightly bound to their nuclei . modest electric forces are not able to pull these electrons free . when an electric force is applied , the electron clouds around the atom stretch and deform in response to the force , but the electrons do not depart . glass , plastic , stone , and air are insulators . even for insulators , though , electric force can always be turned up high enough to rip electrons away—this is called breakdown . that 's what is happening to air molecules when you see a spark . semiconductor materials fall between insulators and conductors . they usually act like insulators , but we can make them act like conductors under certain circumstances . the most well-known semiconductor material is silicon ( atomic number $ 14 $ ) . our ability to finely control the insulating and conducting properties of silicon allows us to create modern marvels like computers and mobile phones . the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current . current is reported as the number of charges per unit time passing through a boundary . visualize placing a boundary all the way through a wire . station yourself near the boundary and count the number of charges passing by . report how much charge passed through the boundary in one second . we assign a positive sign to current corresponding to the direction a positive charge would be moving . since current is the amount of charge passing through a boundary in a fixed amount of time , it can be expressed mathematically using the following equation : $ i = \dfrac { dq } { dt } $ that 's current in a nutshell . a few remarks on current what carries current in metal ? since electrons are free to move about in metals , moving electrons are what makes up the current in metals . the positive nuclei in metal atoms are fixed in place and do not contribute to current . even though electrons have a negative charge and do almost all the work in most electric circuits , we still define a positive current as the direction a positive charge would move . this is a very old historical convention . can current be carried by positive charges ? yes . there are lots of examples . current is carried by both positive and negative charges in saltwater : if we put ordinary table salt in water , it becomes a good conductor . table salt is sodium chloride , nacl . the salt dissolves in water , into free-floating na $ ^+ $ and cl $ ^- $ ions . both ions respond to electric force and move through the saltwater solution , in opposite directions . in this case , the current is composed of moving atoms , both positive and negative ions , not just loose electrons . inside our bodies , electrical currents are moving ions , both positive and negative . the same definition of current works : count the number of charges passing by in a fixed amount of time . what causes current ? charged objects move in response to electric and magnetic forces . these forces come from electric and magnetic fields , which in turn come from the position and motion of other charges . what is the speed of current ? we do n't talk very often about the speed of current . answering the question , `` how fast is the current flowing ? '' requires understanding of a complex physical phenomenon and is not often relevant . current usually is n't about meters per second , it 's about charge per second . more often , we answer the question `` how much current is flowing ? '' all the time . how do we talk about current ? when discussing current , terms like through and in make a lot of sense . current flows through a resistor ; current flows in a wire . if you hear , `` the current across ... '' , it should sound odd . voltage to get our initial toehold on the concept of voltage , let 's look at an analogy : voltage resembles gravity for a mass $ m $ , a change of height $ h $ corresponds to a change in potential energy , $ \delta u = mg\delta h $ . for a charged particle $ q $ , a voltage $ v $ corresponds to a change in potential energy , $ \delta u = qv $ . voltage in an electric circuit is analogous to the product of $ g\cdot \delta h $ . where $ g $ is the acceleration due to gravity and $ \delta h $ is the change of height . a ball at the top of the hill rolls down . when it is halfway down , it has given up half of its potential energy . an electron at the top of a voltage `` hill '' travels `` downhill '' through wires and elements of a circuit . it gives up its potential energy , doing work along the way . when the electron is halfway down the hill , it has given up , or `` dropped '' , half of its potential energy . for both the ball and the electron , the trip down the hill happens spontaneously . the ball and electron move towards a lower energy state all by themselves . on the trip down , there can be things in the way of the ball , like trees or bears to bounce off . for electrons , we can guide electrons using wires and make them flow through electronic components —circuit design— and do interesting things along the way . we can express the voltage between two points mathematically as the change of energy experienced by a charge : $ v = \dfrac { \delta u } { q } $ that 's an intuitive description of voltage in a nutshell . power power is defined as the rate energy ( $ \text u $ ) is transformed or transferred over time . we measure power in units of joules/second , also known as watts . ( $ 1 \ , \text { watt } = 1\ , \text { joule } /\text { second } $ ) $ \text { power } = \dfrac { \text du } { \text dt } $ an electric circuit is capable of transferring power . current is the rate of flow of charge , and voltage measures the energy transferred per unit of charge . we can insert these definitions into the equation for power : $ \text { power } = \dfrac { \text du } { \text dt } = \dfrac { \text du } { \text dq } \cdot \dfrac { \text dq } { \text dt } = v \ , i $ electrical power is the product of voltage times current . in units of watts . summary these mental models for current and voltage will get us started on all sorts of interesting electric circuits . if you want to reach beyond this intuitive description of voltage you can read this more formal mathematical description of electric potential and voltage .
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voltage and current are the cornerstone concepts in electricity . we will create our first mental models for these basic electrical quantities . we will also talk about power , which is what happens when voltage and current act together .
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why do we feel electrical shock when we touch ac source ?
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voltage and current are the cornerstone concepts in electricity . we will create our first mental models for these basic electrical quantities . we will also talk about power , which is what happens when voltage and current act together . charge the concept of electricity arises from an observation of nature . we observe a force between objects , that , like gravity , acts at a distance . the source of this force has been given the name charge . a very noticeable thing about electric force is that it is large , far greater than the force of gravity . unlike gravity , however , there are two types of electric charge . opposite types of charge attract , and like types of charge repel . gravity has only one type : it only attracts , never repels . conductors and insulators conductors are made of atoms whose outer , or valence , electrons have relatively weak bonds to their nuclei , as shown in this fanciful image of a copper atom . when a bunch of metal atoms are together , they gladly share their outer electrons with each other , creating a `` swarm '' of electrons not associated with a particular nucleus . a very small electric force can make the electron swarm move . copper , gold , silver , and aluminum are good conductors . so is saltwater . there are also poor conductors . tungsten—a metal used for light bulb filaments—and carbon—used in graphite form in pencils—are relatively poor conductors because their electrons are less prone to move . insulators are materials whose outer electrons are tightly bound to their nuclei . modest electric forces are not able to pull these electrons free . when an electric force is applied , the electron clouds around the atom stretch and deform in response to the force , but the electrons do not depart . glass , plastic , stone , and air are insulators . even for insulators , though , electric force can always be turned up high enough to rip electrons away—this is called breakdown . that 's what is happening to air molecules when you see a spark . semiconductor materials fall between insulators and conductors . they usually act like insulators , but we can make them act like conductors under certain circumstances . the most well-known semiconductor material is silicon ( atomic number $ 14 $ ) . our ability to finely control the insulating and conducting properties of silicon allows us to create modern marvels like computers and mobile phones . the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current . current is reported as the number of charges per unit time passing through a boundary . visualize placing a boundary all the way through a wire . station yourself near the boundary and count the number of charges passing by . report how much charge passed through the boundary in one second . we assign a positive sign to current corresponding to the direction a positive charge would be moving . since current is the amount of charge passing through a boundary in a fixed amount of time , it can be expressed mathematically using the following equation : $ i = \dfrac { dq } { dt } $ that 's current in a nutshell . a few remarks on current what carries current in metal ? since electrons are free to move about in metals , moving electrons are what makes up the current in metals . the positive nuclei in metal atoms are fixed in place and do not contribute to current . even though electrons have a negative charge and do almost all the work in most electric circuits , we still define a positive current as the direction a positive charge would move . this is a very old historical convention . can current be carried by positive charges ? yes . there are lots of examples . current is carried by both positive and negative charges in saltwater : if we put ordinary table salt in water , it becomes a good conductor . table salt is sodium chloride , nacl . the salt dissolves in water , into free-floating na $ ^+ $ and cl $ ^- $ ions . both ions respond to electric force and move through the saltwater solution , in opposite directions . in this case , the current is composed of moving atoms , both positive and negative ions , not just loose electrons . inside our bodies , electrical currents are moving ions , both positive and negative . the same definition of current works : count the number of charges passing by in a fixed amount of time . what causes current ? charged objects move in response to electric and magnetic forces . these forces come from electric and magnetic fields , which in turn come from the position and motion of other charges . what is the speed of current ? we do n't talk very often about the speed of current . answering the question , `` how fast is the current flowing ? '' requires understanding of a complex physical phenomenon and is not often relevant . current usually is n't about meters per second , it 's about charge per second . more often , we answer the question `` how much current is flowing ? '' all the time . how do we talk about current ? when discussing current , terms like through and in make a lot of sense . current flows through a resistor ; current flows in a wire . if you hear , `` the current across ... '' , it should sound odd . voltage to get our initial toehold on the concept of voltage , let 's look at an analogy : voltage resembles gravity for a mass $ m $ , a change of height $ h $ corresponds to a change in potential energy , $ \delta u = mg\delta h $ . for a charged particle $ q $ , a voltage $ v $ corresponds to a change in potential energy , $ \delta u = qv $ . voltage in an electric circuit is analogous to the product of $ g\cdot \delta h $ . where $ g $ is the acceleration due to gravity and $ \delta h $ is the change of height . a ball at the top of the hill rolls down . when it is halfway down , it has given up half of its potential energy . an electron at the top of a voltage `` hill '' travels `` downhill '' through wires and elements of a circuit . it gives up its potential energy , doing work along the way . when the electron is halfway down the hill , it has given up , or `` dropped '' , half of its potential energy . for both the ball and the electron , the trip down the hill happens spontaneously . the ball and electron move towards a lower energy state all by themselves . on the trip down , there can be things in the way of the ball , like trees or bears to bounce off . for electrons , we can guide electrons using wires and make them flow through electronic components —circuit design— and do interesting things along the way . we can express the voltage between two points mathematically as the change of energy experienced by a charge : $ v = \dfrac { \delta u } { q } $ that 's an intuitive description of voltage in a nutshell . power power is defined as the rate energy ( $ \text u $ ) is transformed or transferred over time . we measure power in units of joules/second , also known as watts . ( $ 1 \ , \text { watt } = 1\ , \text { joule } /\text { second } $ ) $ \text { power } = \dfrac { \text du } { \text dt } $ an electric circuit is capable of transferring power . current is the rate of flow of charge , and voltage measures the energy transferred per unit of charge . we can insert these definitions into the equation for power : $ \text { power } = \dfrac { \text du } { \text dt } = \dfrac { \text du } { \text dq } \cdot \dfrac { \text dq } { \text dt } = v \ , i $ electrical power is the product of voltage times current . in units of watts . summary these mental models for current and voltage will get us started on all sorts of interesting electric circuits . if you want to reach beyond this intuitive description of voltage you can read this more formal mathematical description of electric potential and voltage .
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what is the speed of current ? we do n't talk very often about the speed of current . answering the question , `` how fast is the current flowing ? ''
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why do n't we feel while touching a dc ?
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voltage and current are the cornerstone concepts in electricity . we will create our first mental models for these basic electrical quantities . we will also talk about power , which is what happens when voltage and current act together . charge the concept of electricity arises from an observation of nature . we observe a force between objects , that , like gravity , acts at a distance . the source of this force has been given the name charge . a very noticeable thing about electric force is that it is large , far greater than the force of gravity . unlike gravity , however , there are two types of electric charge . opposite types of charge attract , and like types of charge repel . gravity has only one type : it only attracts , never repels . conductors and insulators conductors are made of atoms whose outer , or valence , electrons have relatively weak bonds to their nuclei , as shown in this fanciful image of a copper atom . when a bunch of metal atoms are together , they gladly share their outer electrons with each other , creating a `` swarm '' of electrons not associated with a particular nucleus . a very small electric force can make the electron swarm move . copper , gold , silver , and aluminum are good conductors . so is saltwater . there are also poor conductors . tungsten—a metal used for light bulb filaments—and carbon—used in graphite form in pencils—are relatively poor conductors because their electrons are less prone to move . insulators are materials whose outer electrons are tightly bound to their nuclei . modest electric forces are not able to pull these electrons free . when an electric force is applied , the electron clouds around the atom stretch and deform in response to the force , but the electrons do not depart . glass , plastic , stone , and air are insulators . even for insulators , though , electric force can always be turned up high enough to rip electrons away—this is called breakdown . that 's what is happening to air molecules when you see a spark . semiconductor materials fall between insulators and conductors . they usually act like insulators , but we can make them act like conductors under certain circumstances . the most well-known semiconductor material is silicon ( atomic number $ 14 $ ) . our ability to finely control the insulating and conducting properties of silicon allows us to create modern marvels like computers and mobile phones . the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current . current is reported as the number of charges per unit time passing through a boundary . visualize placing a boundary all the way through a wire . station yourself near the boundary and count the number of charges passing by . report how much charge passed through the boundary in one second . we assign a positive sign to current corresponding to the direction a positive charge would be moving . since current is the amount of charge passing through a boundary in a fixed amount of time , it can be expressed mathematically using the following equation : $ i = \dfrac { dq } { dt } $ that 's current in a nutshell . a few remarks on current what carries current in metal ? since electrons are free to move about in metals , moving electrons are what makes up the current in metals . the positive nuclei in metal atoms are fixed in place and do not contribute to current . even though electrons have a negative charge and do almost all the work in most electric circuits , we still define a positive current as the direction a positive charge would move . this is a very old historical convention . can current be carried by positive charges ? yes . there are lots of examples . current is carried by both positive and negative charges in saltwater : if we put ordinary table salt in water , it becomes a good conductor . table salt is sodium chloride , nacl . the salt dissolves in water , into free-floating na $ ^+ $ and cl $ ^- $ ions . both ions respond to electric force and move through the saltwater solution , in opposite directions . in this case , the current is composed of moving atoms , both positive and negative ions , not just loose electrons . inside our bodies , electrical currents are moving ions , both positive and negative . the same definition of current works : count the number of charges passing by in a fixed amount of time . what causes current ? charged objects move in response to electric and magnetic forces . these forces come from electric and magnetic fields , which in turn come from the position and motion of other charges . what is the speed of current ? we do n't talk very often about the speed of current . answering the question , `` how fast is the current flowing ? '' requires understanding of a complex physical phenomenon and is not often relevant . current usually is n't about meters per second , it 's about charge per second . more often , we answer the question `` how much current is flowing ? '' all the time . how do we talk about current ? when discussing current , terms like through and in make a lot of sense . current flows through a resistor ; current flows in a wire . if you hear , `` the current across ... '' , it should sound odd . voltage to get our initial toehold on the concept of voltage , let 's look at an analogy : voltage resembles gravity for a mass $ m $ , a change of height $ h $ corresponds to a change in potential energy , $ \delta u = mg\delta h $ . for a charged particle $ q $ , a voltage $ v $ corresponds to a change in potential energy , $ \delta u = qv $ . voltage in an electric circuit is analogous to the product of $ g\cdot \delta h $ . where $ g $ is the acceleration due to gravity and $ \delta h $ is the change of height . a ball at the top of the hill rolls down . when it is halfway down , it has given up half of its potential energy . an electron at the top of a voltage `` hill '' travels `` downhill '' through wires and elements of a circuit . it gives up its potential energy , doing work along the way . when the electron is halfway down the hill , it has given up , or `` dropped '' , half of its potential energy . for both the ball and the electron , the trip down the hill happens spontaneously . the ball and electron move towards a lower energy state all by themselves . on the trip down , there can be things in the way of the ball , like trees or bears to bounce off . for electrons , we can guide electrons using wires and make them flow through electronic components —circuit design— and do interesting things along the way . we can express the voltage between two points mathematically as the change of energy experienced by a charge : $ v = \dfrac { \delta u } { q } $ that 's an intuitive description of voltage in a nutshell . power power is defined as the rate energy ( $ \text u $ ) is transformed or transferred over time . we measure power in units of joules/second , also known as watts . ( $ 1 \ , \text { watt } = 1\ , \text { joule } /\text { second } $ ) $ \text { power } = \dfrac { \text du } { \text dt } $ an electric circuit is capable of transferring power . current is the rate of flow of charge , and voltage measures the energy transferred per unit of charge . we can insert these definitions into the equation for power : $ \text { power } = \dfrac { \text du } { \text dt } = \dfrac { \text du } { \text dq } \cdot \dfrac { \text dq } { \text dt } = v \ , i $ electrical power is the product of voltage times current . in units of watts . summary these mental models for current and voltage will get us started on all sorts of interesting electric circuits . if you want to reach beyond this intuitive description of voltage you can read this more formal mathematical description of electric potential and voltage .
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table salt is sodium chloride , nacl . the salt dissolves in water , into free-floating na $ ^+ $ and cl $ ^- $ ions . both ions respond to electric force and move through the saltwater solution , in opposite directions .
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since it is a measure of potential , can voltage be thought of the diameter of a water hose and the charge as the amount of water flowing through it ?
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voltage and current are the cornerstone concepts in electricity . we will create our first mental models for these basic electrical quantities . we will also talk about power , which is what happens when voltage and current act together . charge the concept of electricity arises from an observation of nature . we observe a force between objects , that , like gravity , acts at a distance . the source of this force has been given the name charge . a very noticeable thing about electric force is that it is large , far greater than the force of gravity . unlike gravity , however , there are two types of electric charge . opposite types of charge attract , and like types of charge repel . gravity has only one type : it only attracts , never repels . conductors and insulators conductors are made of atoms whose outer , or valence , electrons have relatively weak bonds to their nuclei , as shown in this fanciful image of a copper atom . when a bunch of metal atoms are together , they gladly share their outer electrons with each other , creating a `` swarm '' of electrons not associated with a particular nucleus . a very small electric force can make the electron swarm move . copper , gold , silver , and aluminum are good conductors . so is saltwater . there are also poor conductors . tungsten—a metal used for light bulb filaments—and carbon—used in graphite form in pencils—are relatively poor conductors because their electrons are less prone to move . insulators are materials whose outer electrons are tightly bound to their nuclei . modest electric forces are not able to pull these electrons free . when an electric force is applied , the electron clouds around the atom stretch and deform in response to the force , but the electrons do not depart . glass , plastic , stone , and air are insulators . even for insulators , though , electric force can always be turned up high enough to rip electrons away—this is called breakdown . that 's what is happening to air molecules when you see a spark . semiconductor materials fall between insulators and conductors . they usually act like insulators , but we can make them act like conductors under certain circumstances . the most well-known semiconductor material is silicon ( atomic number $ 14 $ ) . our ability to finely control the insulating and conducting properties of silicon allows us to create modern marvels like computers and mobile phones . the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current . current is reported as the number of charges per unit time passing through a boundary . visualize placing a boundary all the way through a wire . station yourself near the boundary and count the number of charges passing by . report how much charge passed through the boundary in one second . we assign a positive sign to current corresponding to the direction a positive charge would be moving . since current is the amount of charge passing through a boundary in a fixed amount of time , it can be expressed mathematically using the following equation : $ i = \dfrac { dq } { dt } $ that 's current in a nutshell . a few remarks on current what carries current in metal ? since electrons are free to move about in metals , moving electrons are what makes up the current in metals . the positive nuclei in metal atoms are fixed in place and do not contribute to current . even though electrons have a negative charge and do almost all the work in most electric circuits , we still define a positive current as the direction a positive charge would move . this is a very old historical convention . can current be carried by positive charges ? yes . there are lots of examples . current is carried by both positive and negative charges in saltwater : if we put ordinary table salt in water , it becomes a good conductor . table salt is sodium chloride , nacl . the salt dissolves in water , into free-floating na $ ^+ $ and cl $ ^- $ ions . both ions respond to electric force and move through the saltwater solution , in opposite directions . in this case , the current is composed of moving atoms , both positive and negative ions , not just loose electrons . inside our bodies , electrical currents are moving ions , both positive and negative . the same definition of current works : count the number of charges passing by in a fixed amount of time . what causes current ? charged objects move in response to electric and magnetic forces . these forces come from electric and magnetic fields , which in turn come from the position and motion of other charges . what is the speed of current ? we do n't talk very often about the speed of current . answering the question , `` how fast is the current flowing ? '' requires understanding of a complex physical phenomenon and is not often relevant . current usually is n't about meters per second , it 's about charge per second . more often , we answer the question `` how much current is flowing ? '' all the time . how do we talk about current ? when discussing current , terms like through and in make a lot of sense . current flows through a resistor ; current flows in a wire . if you hear , `` the current across ... '' , it should sound odd . voltage to get our initial toehold on the concept of voltage , let 's look at an analogy : voltage resembles gravity for a mass $ m $ , a change of height $ h $ corresponds to a change in potential energy , $ \delta u = mg\delta h $ . for a charged particle $ q $ , a voltage $ v $ corresponds to a change in potential energy , $ \delta u = qv $ . voltage in an electric circuit is analogous to the product of $ g\cdot \delta h $ . where $ g $ is the acceleration due to gravity and $ \delta h $ is the change of height . a ball at the top of the hill rolls down . when it is halfway down , it has given up half of its potential energy . an electron at the top of a voltage `` hill '' travels `` downhill '' through wires and elements of a circuit . it gives up its potential energy , doing work along the way . when the electron is halfway down the hill , it has given up , or `` dropped '' , half of its potential energy . for both the ball and the electron , the trip down the hill happens spontaneously . the ball and electron move towards a lower energy state all by themselves . on the trip down , there can be things in the way of the ball , like trees or bears to bounce off . for electrons , we can guide electrons using wires and make them flow through electronic components —circuit design— and do interesting things along the way . we can express the voltage between two points mathematically as the change of energy experienced by a charge : $ v = \dfrac { \delta u } { q } $ that 's an intuitive description of voltage in a nutshell . power power is defined as the rate energy ( $ \text u $ ) is transformed or transferred over time . we measure power in units of joules/second , also known as watts . ( $ 1 \ , \text { watt } = 1\ , \text { joule } /\text { second } $ ) $ \text { power } = \dfrac { \text du } { \text dt } $ an electric circuit is capable of transferring power . current is the rate of flow of charge , and voltage measures the energy transferred per unit of charge . we can insert these definitions into the equation for power : $ \text { power } = \dfrac { \text du } { \text dt } = \dfrac { \text du } { \text dq } \cdot \dfrac { \text dq } { \text dt } = v \ , i $ electrical power is the product of voltage times current . in units of watts . summary these mental models for current and voltage will get us started on all sorts of interesting electric circuits . if you want to reach beyond this intuitive description of voltage you can read this more formal mathematical description of electric potential and voltage .
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station yourself near the boundary and count the number of charges passing by . report how much charge passed through the boundary in one second . we assign a positive sign to current corresponding to the direction a positive charge would be moving .
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of charge moving in one meter ?
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voltage and current are the cornerstone concepts in electricity . we will create our first mental models for these basic electrical quantities . we will also talk about power , which is what happens when voltage and current act together . charge the concept of electricity arises from an observation of nature . we observe a force between objects , that , like gravity , acts at a distance . the source of this force has been given the name charge . a very noticeable thing about electric force is that it is large , far greater than the force of gravity . unlike gravity , however , there are two types of electric charge . opposite types of charge attract , and like types of charge repel . gravity has only one type : it only attracts , never repels . conductors and insulators conductors are made of atoms whose outer , or valence , electrons have relatively weak bonds to their nuclei , as shown in this fanciful image of a copper atom . when a bunch of metal atoms are together , they gladly share their outer electrons with each other , creating a `` swarm '' of electrons not associated with a particular nucleus . a very small electric force can make the electron swarm move . copper , gold , silver , and aluminum are good conductors . so is saltwater . there are also poor conductors . tungsten—a metal used for light bulb filaments—and carbon—used in graphite form in pencils—are relatively poor conductors because their electrons are less prone to move . insulators are materials whose outer electrons are tightly bound to their nuclei . modest electric forces are not able to pull these electrons free . when an electric force is applied , the electron clouds around the atom stretch and deform in response to the force , but the electrons do not depart . glass , plastic , stone , and air are insulators . even for insulators , though , electric force can always be turned up high enough to rip electrons away—this is called breakdown . that 's what is happening to air molecules when you see a spark . semiconductor materials fall between insulators and conductors . they usually act like insulators , but we can make them act like conductors under certain circumstances . the most well-known semiconductor material is silicon ( atomic number $ 14 $ ) . our ability to finely control the insulating and conducting properties of silicon allows us to create modern marvels like computers and mobile phones . the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current . current is reported as the number of charges per unit time passing through a boundary . visualize placing a boundary all the way through a wire . station yourself near the boundary and count the number of charges passing by . report how much charge passed through the boundary in one second . we assign a positive sign to current corresponding to the direction a positive charge would be moving . since current is the amount of charge passing through a boundary in a fixed amount of time , it can be expressed mathematically using the following equation : $ i = \dfrac { dq } { dt } $ that 's current in a nutshell . a few remarks on current what carries current in metal ? since electrons are free to move about in metals , moving electrons are what makes up the current in metals . the positive nuclei in metal atoms are fixed in place and do not contribute to current . even though electrons have a negative charge and do almost all the work in most electric circuits , we still define a positive current as the direction a positive charge would move . this is a very old historical convention . can current be carried by positive charges ? yes . there are lots of examples . current is carried by both positive and negative charges in saltwater : if we put ordinary table salt in water , it becomes a good conductor . table salt is sodium chloride , nacl . the salt dissolves in water , into free-floating na $ ^+ $ and cl $ ^- $ ions . both ions respond to electric force and move through the saltwater solution , in opposite directions . in this case , the current is composed of moving atoms , both positive and negative ions , not just loose electrons . inside our bodies , electrical currents are moving ions , both positive and negative . the same definition of current works : count the number of charges passing by in a fixed amount of time . what causes current ? charged objects move in response to electric and magnetic forces . these forces come from electric and magnetic fields , which in turn come from the position and motion of other charges . what is the speed of current ? we do n't talk very often about the speed of current . answering the question , `` how fast is the current flowing ? '' requires understanding of a complex physical phenomenon and is not often relevant . current usually is n't about meters per second , it 's about charge per second . more often , we answer the question `` how much current is flowing ? '' all the time . how do we talk about current ? when discussing current , terms like through and in make a lot of sense . current flows through a resistor ; current flows in a wire . if you hear , `` the current across ... '' , it should sound odd . voltage to get our initial toehold on the concept of voltage , let 's look at an analogy : voltage resembles gravity for a mass $ m $ , a change of height $ h $ corresponds to a change in potential energy , $ \delta u = mg\delta h $ . for a charged particle $ q $ , a voltage $ v $ corresponds to a change in potential energy , $ \delta u = qv $ . voltage in an electric circuit is analogous to the product of $ g\cdot \delta h $ . where $ g $ is the acceleration due to gravity and $ \delta h $ is the change of height . a ball at the top of the hill rolls down . when it is halfway down , it has given up half of its potential energy . an electron at the top of a voltage `` hill '' travels `` downhill '' through wires and elements of a circuit . it gives up its potential energy , doing work along the way . when the electron is halfway down the hill , it has given up , or `` dropped '' , half of its potential energy . for both the ball and the electron , the trip down the hill happens spontaneously . the ball and electron move towards a lower energy state all by themselves . on the trip down , there can be things in the way of the ball , like trees or bears to bounce off . for electrons , we can guide electrons using wires and make them flow through electronic components —circuit design— and do interesting things along the way . we can express the voltage between two points mathematically as the change of energy experienced by a charge : $ v = \dfrac { \delta u } { q } $ that 's an intuitive description of voltage in a nutshell . power power is defined as the rate energy ( $ \text u $ ) is transformed or transferred over time . we measure power in units of joules/second , also known as watts . ( $ 1 \ , \text { watt } = 1\ , \text { joule } /\text { second } $ ) $ \text { power } = \dfrac { \text du } { \text dt } $ an electric circuit is capable of transferring power . current is the rate of flow of charge , and voltage measures the energy transferred per unit of charge . we can insert these definitions into the equation for power : $ \text { power } = \dfrac { \text du } { \text dt } = \dfrac { \text du } { \text dq } \cdot \dfrac { \text dq } { \text dt } = v \ , i $ electrical power is the product of voltage times current . in units of watts . summary these mental models for current and voltage will get us started on all sorts of interesting electric circuits . if you want to reach beyond this intuitive description of voltage you can read this more formal mathematical description of electric potential and voltage .
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unlike gravity , however , there are two types of electric charge . opposite types of charge attract , and like types of charge repel . gravity has only one type : it only attracts , never repels .
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what is the need of storing charge ?
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voltage and current are the cornerstone concepts in electricity . we will create our first mental models for these basic electrical quantities . we will also talk about power , which is what happens when voltage and current act together . charge the concept of electricity arises from an observation of nature . we observe a force between objects , that , like gravity , acts at a distance . the source of this force has been given the name charge . a very noticeable thing about electric force is that it is large , far greater than the force of gravity . unlike gravity , however , there are two types of electric charge . opposite types of charge attract , and like types of charge repel . gravity has only one type : it only attracts , never repels . conductors and insulators conductors are made of atoms whose outer , or valence , electrons have relatively weak bonds to their nuclei , as shown in this fanciful image of a copper atom . when a bunch of metal atoms are together , they gladly share their outer electrons with each other , creating a `` swarm '' of electrons not associated with a particular nucleus . a very small electric force can make the electron swarm move . copper , gold , silver , and aluminum are good conductors . so is saltwater . there are also poor conductors . tungsten—a metal used for light bulb filaments—and carbon—used in graphite form in pencils—are relatively poor conductors because their electrons are less prone to move . insulators are materials whose outer electrons are tightly bound to their nuclei . modest electric forces are not able to pull these electrons free . when an electric force is applied , the electron clouds around the atom stretch and deform in response to the force , but the electrons do not depart . glass , plastic , stone , and air are insulators . even for insulators , though , electric force can always be turned up high enough to rip electrons away—this is called breakdown . that 's what is happening to air molecules when you see a spark . semiconductor materials fall between insulators and conductors . they usually act like insulators , but we can make them act like conductors under certain circumstances . the most well-known semiconductor material is silicon ( atomic number $ 14 $ ) . our ability to finely control the insulating and conducting properties of silicon allows us to create modern marvels like computers and mobile phones . the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current . current is reported as the number of charges per unit time passing through a boundary . visualize placing a boundary all the way through a wire . station yourself near the boundary and count the number of charges passing by . report how much charge passed through the boundary in one second . we assign a positive sign to current corresponding to the direction a positive charge would be moving . since current is the amount of charge passing through a boundary in a fixed amount of time , it can be expressed mathematically using the following equation : $ i = \dfrac { dq } { dt } $ that 's current in a nutshell . a few remarks on current what carries current in metal ? since electrons are free to move about in metals , moving electrons are what makes up the current in metals . the positive nuclei in metal atoms are fixed in place and do not contribute to current . even though electrons have a negative charge and do almost all the work in most electric circuits , we still define a positive current as the direction a positive charge would move . this is a very old historical convention . can current be carried by positive charges ? yes . there are lots of examples . current is carried by both positive and negative charges in saltwater : if we put ordinary table salt in water , it becomes a good conductor . table salt is sodium chloride , nacl . the salt dissolves in water , into free-floating na $ ^+ $ and cl $ ^- $ ions . both ions respond to electric force and move through the saltwater solution , in opposite directions . in this case , the current is composed of moving atoms , both positive and negative ions , not just loose electrons . inside our bodies , electrical currents are moving ions , both positive and negative . the same definition of current works : count the number of charges passing by in a fixed amount of time . what causes current ? charged objects move in response to electric and magnetic forces . these forces come from electric and magnetic fields , which in turn come from the position and motion of other charges . what is the speed of current ? we do n't talk very often about the speed of current . answering the question , `` how fast is the current flowing ? '' requires understanding of a complex physical phenomenon and is not often relevant . current usually is n't about meters per second , it 's about charge per second . more often , we answer the question `` how much current is flowing ? '' all the time . how do we talk about current ? when discussing current , terms like through and in make a lot of sense . current flows through a resistor ; current flows in a wire . if you hear , `` the current across ... '' , it should sound odd . voltage to get our initial toehold on the concept of voltage , let 's look at an analogy : voltage resembles gravity for a mass $ m $ , a change of height $ h $ corresponds to a change in potential energy , $ \delta u = mg\delta h $ . for a charged particle $ q $ , a voltage $ v $ corresponds to a change in potential energy , $ \delta u = qv $ . voltage in an electric circuit is analogous to the product of $ g\cdot \delta h $ . where $ g $ is the acceleration due to gravity and $ \delta h $ is the change of height . a ball at the top of the hill rolls down . when it is halfway down , it has given up half of its potential energy . an electron at the top of a voltage `` hill '' travels `` downhill '' through wires and elements of a circuit . it gives up its potential energy , doing work along the way . when the electron is halfway down the hill , it has given up , or `` dropped '' , half of its potential energy . for both the ball and the electron , the trip down the hill happens spontaneously . the ball and electron move towards a lower energy state all by themselves . on the trip down , there can be things in the way of the ball , like trees or bears to bounce off . for electrons , we can guide electrons using wires and make them flow through electronic components —circuit design— and do interesting things along the way . we can express the voltage between two points mathematically as the change of energy experienced by a charge : $ v = \dfrac { \delta u } { q } $ that 's an intuitive description of voltage in a nutshell . power power is defined as the rate energy ( $ \text u $ ) is transformed or transferred over time . we measure power in units of joules/second , also known as watts . ( $ 1 \ , \text { watt } = 1\ , \text { joule } /\text { second } $ ) $ \text { power } = \dfrac { \text du } { \text dt } $ an electric circuit is capable of transferring power . current is the rate of flow of charge , and voltage measures the energy transferred per unit of charge . we can insert these definitions into the equation for power : $ \text { power } = \dfrac { \text du } { \text dt } = \dfrac { \text du } { \text dq } \cdot \dfrac { \text dq } { \text dt } = v \ , i $ electrical power is the product of voltage times current . in units of watts . summary these mental models for current and voltage will get us started on all sorts of interesting electric circuits . if you want to reach beyond this intuitive description of voltage you can read this more formal mathematical description of electric potential and voltage .
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voltage and current are the cornerstone concepts in electricity . we will create our first mental models for these basic electrical quantities .
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can someone describe voltage and current with some different examples ?
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voltage and current are the cornerstone concepts in electricity . we will create our first mental models for these basic electrical quantities . we will also talk about power , which is what happens when voltage and current act together . charge the concept of electricity arises from an observation of nature . we observe a force between objects , that , like gravity , acts at a distance . the source of this force has been given the name charge . a very noticeable thing about electric force is that it is large , far greater than the force of gravity . unlike gravity , however , there are two types of electric charge . opposite types of charge attract , and like types of charge repel . gravity has only one type : it only attracts , never repels . conductors and insulators conductors are made of atoms whose outer , or valence , electrons have relatively weak bonds to their nuclei , as shown in this fanciful image of a copper atom . when a bunch of metal atoms are together , they gladly share their outer electrons with each other , creating a `` swarm '' of electrons not associated with a particular nucleus . a very small electric force can make the electron swarm move . copper , gold , silver , and aluminum are good conductors . so is saltwater . there are also poor conductors . tungsten—a metal used for light bulb filaments—and carbon—used in graphite form in pencils—are relatively poor conductors because their electrons are less prone to move . insulators are materials whose outer electrons are tightly bound to their nuclei . modest electric forces are not able to pull these electrons free . when an electric force is applied , the electron clouds around the atom stretch and deform in response to the force , but the electrons do not depart . glass , plastic , stone , and air are insulators . even for insulators , though , electric force can always be turned up high enough to rip electrons away—this is called breakdown . that 's what is happening to air molecules when you see a spark . semiconductor materials fall between insulators and conductors . they usually act like insulators , but we can make them act like conductors under certain circumstances . the most well-known semiconductor material is silicon ( atomic number $ 14 $ ) . our ability to finely control the insulating and conducting properties of silicon allows us to create modern marvels like computers and mobile phones . the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current . current is reported as the number of charges per unit time passing through a boundary . visualize placing a boundary all the way through a wire . station yourself near the boundary and count the number of charges passing by . report how much charge passed through the boundary in one second . we assign a positive sign to current corresponding to the direction a positive charge would be moving . since current is the amount of charge passing through a boundary in a fixed amount of time , it can be expressed mathematically using the following equation : $ i = \dfrac { dq } { dt } $ that 's current in a nutshell . a few remarks on current what carries current in metal ? since electrons are free to move about in metals , moving electrons are what makes up the current in metals . the positive nuclei in metal atoms are fixed in place and do not contribute to current . even though electrons have a negative charge and do almost all the work in most electric circuits , we still define a positive current as the direction a positive charge would move . this is a very old historical convention . can current be carried by positive charges ? yes . there are lots of examples . current is carried by both positive and negative charges in saltwater : if we put ordinary table salt in water , it becomes a good conductor . table salt is sodium chloride , nacl . the salt dissolves in water , into free-floating na $ ^+ $ and cl $ ^- $ ions . both ions respond to electric force and move through the saltwater solution , in opposite directions . in this case , the current is composed of moving atoms , both positive and negative ions , not just loose electrons . inside our bodies , electrical currents are moving ions , both positive and negative . the same definition of current works : count the number of charges passing by in a fixed amount of time . what causes current ? charged objects move in response to electric and magnetic forces . these forces come from electric and magnetic fields , which in turn come from the position and motion of other charges . what is the speed of current ? we do n't talk very often about the speed of current . answering the question , `` how fast is the current flowing ? '' requires understanding of a complex physical phenomenon and is not often relevant . current usually is n't about meters per second , it 's about charge per second . more often , we answer the question `` how much current is flowing ? '' all the time . how do we talk about current ? when discussing current , terms like through and in make a lot of sense . current flows through a resistor ; current flows in a wire . if you hear , `` the current across ... '' , it should sound odd . voltage to get our initial toehold on the concept of voltage , let 's look at an analogy : voltage resembles gravity for a mass $ m $ , a change of height $ h $ corresponds to a change in potential energy , $ \delta u = mg\delta h $ . for a charged particle $ q $ , a voltage $ v $ corresponds to a change in potential energy , $ \delta u = qv $ . voltage in an electric circuit is analogous to the product of $ g\cdot \delta h $ . where $ g $ is the acceleration due to gravity and $ \delta h $ is the change of height . a ball at the top of the hill rolls down . when it is halfway down , it has given up half of its potential energy . an electron at the top of a voltage `` hill '' travels `` downhill '' through wires and elements of a circuit . it gives up its potential energy , doing work along the way . when the electron is halfway down the hill , it has given up , or `` dropped '' , half of its potential energy . for both the ball and the electron , the trip down the hill happens spontaneously . the ball and electron move towards a lower energy state all by themselves . on the trip down , there can be things in the way of the ball , like trees or bears to bounce off . for electrons , we can guide electrons using wires and make them flow through electronic components —circuit design— and do interesting things along the way . we can express the voltage between two points mathematically as the change of energy experienced by a charge : $ v = \dfrac { \delta u } { q } $ that 's an intuitive description of voltage in a nutshell . power power is defined as the rate energy ( $ \text u $ ) is transformed or transferred over time . we measure power in units of joules/second , also known as watts . ( $ 1 \ , \text { watt } = 1\ , \text { joule } /\text { second } $ ) $ \text { power } = \dfrac { \text du } { \text dt } $ an electric circuit is capable of transferring power . current is the rate of flow of charge , and voltage measures the energy transferred per unit of charge . we can insert these definitions into the equation for power : $ \text { power } = \dfrac { \text du } { \text dt } = \dfrac { \text du } { \text dq } \cdot \dfrac { \text dq } { \text dt } = v \ , i $ electrical power is the product of voltage times current . in units of watts . summary these mental models for current and voltage will get us started on all sorts of interesting electric circuits . if you want to reach beyond this intuitive description of voltage you can read this more formal mathematical description of electric potential and voltage .
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for a charged particle $ q $ , a voltage $ v $ corresponds to a change in potential energy , $ \delta u = qv $ . voltage in an electric circuit is analogous to the product of $ g\cdot \delta h $ . where $ g $ is the acceleration due to gravity and $ \delta h $ is the change of height .
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what is the role of battery/ voltage source in a circuit ?
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voltage and current are the cornerstone concepts in electricity . we will create our first mental models for these basic electrical quantities . we will also talk about power , which is what happens when voltage and current act together . charge the concept of electricity arises from an observation of nature . we observe a force between objects , that , like gravity , acts at a distance . the source of this force has been given the name charge . a very noticeable thing about electric force is that it is large , far greater than the force of gravity . unlike gravity , however , there are two types of electric charge . opposite types of charge attract , and like types of charge repel . gravity has only one type : it only attracts , never repels . conductors and insulators conductors are made of atoms whose outer , or valence , electrons have relatively weak bonds to their nuclei , as shown in this fanciful image of a copper atom . when a bunch of metal atoms are together , they gladly share their outer electrons with each other , creating a `` swarm '' of electrons not associated with a particular nucleus . a very small electric force can make the electron swarm move . copper , gold , silver , and aluminum are good conductors . so is saltwater . there are also poor conductors . tungsten—a metal used for light bulb filaments—and carbon—used in graphite form in pencils—are relatively poor conductors because their electrons are less prone to move . insulators are materials whose outer electrons are tightly bound to their nuclei . modest electric forces are not able to pull these electrons free . when an electric force is applied , the electron clouds around the atom stretch and deform in response to the force , but the electrons do not depart . glass , plastic , stone , and air are insulators . even for insulators , though , electric force can always be turned up high enough to rip electrons away—this is called breakdown . that 's what is happening to air molecules when you see a spark . semiconductor materials fall between insulators and conductors . they usually act like insulators , but we can make them act like conductors under certain circumstances . the most well-known semiconductor material is silicon ( atomic number $ 14 $ ) . our ability to finely control the insulating and conducting properties of silicon allows us to create modern marvels like computers and mobile phones . the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current . current is reported as the number of charges per unit time passing through a boundary . visualize placing a boundary all the way through a wire . station yourself near the boundary and count the number of charges passing by . report how much charge passed through the boundary in one second . we assign a positive sign to current corresponding to the direction a positive charge would be moving . since current is the amount of charge passing through a boundary in a fixed amount of time , it can be expressed mathematically using the following equation : $ i = \dfrac { dq } { dt } $ that 's current in a nutshell . a few remarks on current what carries current in metal ? since electrons are free to move about in metals , moving electrons are what makes up the current in metals . the positive nuclei in metal atoms are fixed in place and do not contribute to current . even though electrons have a negative charge and do almost all the work in most electric circuits , we still define a positive current as the direction a positive charge would move . this is a very old historical convention . can current be carried by positive charges ? yes . there are lots of examples . current is carried by both positive and negative charges in saltwater : if we put ordinary table salt in water , it becomes a good conductor . table salt is sodium chloride , nacl . the salt dissolves in water , into free-floating na $ ^+ $ and cl $ ^- $ ions . both ions respond to electric force and move through the saltwater solution , in opposite directions . in this case , the current is composed of moving atoms , both positive and negative ions , not just loose electrons . inside our bodies , electrical currents are moving ions , both positive and negative . the same definition of current works : count the number of charges passing by in a fixed amount of time . what causes current ? charged objects move in response to electric and magnetic forces . these forces come from electric and magnetic fields , which in turn come from the position and motion of other charges . what is the speed of current ? we do n't talk very often about the speed of current . answering the question , `` how fast is the current flowing ? '' requires understanding of a complex physical phenomenon and is not often relevant . current usually is n't about meters per second , it 's about charge per second . more often , we answer the question `` how much current is flowing ? '' all the time . how do we talk about current ? when discussing current , terms like through and in make a lot of sense . current flows through a resistor ; current flows in a wire . if you hear , `` the current across ... '' , it should sound odd . voltage to get our initial toehold on the concept of voltage , let 's look at an analogy : voltage resembles gravity for a mass $ m $ , a change of height $ h $ corresponds to a change in potential energy , $ \delta u = mg\delta h $ . for a charged particle $ q $ , a voltage $ v $ corresponds to a change in potential energy , $ \delta u = qv $ . voltage in an electric circuit is analogous to the product of $ g\cdot \delta h $ . where $ g $ is the acceleration due to gravity and $ \delta h $ is the change of height . a ball at the top of the hill rolls down . when it is halfway down , it has given up half of its potential energy . an electron at the top of a voltage `` hill '' travels `` downhill '' through wires and elements of a circuit . it gives up its potential energy , doing work along the way . when the electron is halfway down the hill , it has given up , or `` dropped '' , half of its potential energy . for both the ball and the electron , the trip down the hill happens spontaneously . the ball and electron move towards a lower energy state all by themselves . on the trip down , there can be things in the way of the ball , like trees or bears to bounce off . for electrons , we can guide electrons using wires and make them flow through electronic components —circuit design— and do interesting things along the way . we can express the voltage between two points mathematically as the change of energy experienced by a charge : $ v = \dfrac { \delta u } { q } $ that 's an intuitive description of voltage in a nutshell . power power is defined as the rate energy ( $ \text u $ ) is transformed or transferred over time . we measure power in units of joules/second , also known as watts . ( $ 1 \ , \text { watt } = 1\ , \text { joule } /\text { second } $ ) $ \text { power } = \dfrac { \text du } { \text dt } $ an electric circuit is capable of transferring power . current is the rate of flow of charge , and voltage measures the energy transferred per unit of charge . we can insert these definitions into the equation for power : $ \text { power } = \dfrac { \text du } { \text dt } = \dfrac { \text du } { \text dq } \cdot \dfrac { \text dq } { \text dt } = v \ , i $ electrical power is the product of voltage times current . in units of watts . summary these mental models for current and voltage will get us started on all sorts of interesting electric circuits . if you want to reach beyond this intuitive description of voltage you can read this more formal mathematical description of electric potential and voltage .
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when discussing current , terms like through and in make a lot of sense . current flows through a resistor ; current flows in a wire . if you hear , `` the current across ... '' , it should sound odd .
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if current is the amount of charge passing by in an arbitrary amount of time and not necessarily the speed of the electrons , does that mean that a thicker wire would have a higher current than a thinner wire , even if the electrons were travelling at the same speed , because the thicker wire has more electrons per cross section ?
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voltage and current are the cornerstone concepts in electricity . we will create our first mental models for these basic electrical quantities . we will also talk about power , which is what happens when voltage and current act together . charge the concept of electricity arises from an observation of nature . we observe a force between objects , that , like gravity , acts at a distance . the source of this force has been given the name charge . a very noticeable thing about electric force is that it is large , far greater than the force of gravity . unlike gravity , however , there are two types of electric charge . opposite types of charge attract , and like types of charge repel . gravity has only one type : it only attracts , never repels . conductors and insulators conductors are made of atoms whose outer , or valence , electrons have relatively weak bonds to their nuclei , as shown in this fanciful image of a copper atom . when a bunch of metal atoms are together , they gladly share their outer electrons with each other , creating a `` swarm '' of electrons not associated with a particular nucleus . a very small electric force can make the electron swarm move . copper , gold , silver , and aluminum are good conductors . so is saltwater . there are also poor conductors . tungsten—a metal used for light bulb filaments—and carbon—used in graphite form in pencils—are relatively poor conductors because their electrons are less prone to move . insulators are materials whose outer electrons are tightly bound to their nuclei . modest electric forces are not able to pull these electrons free . when an electric force is applied , the electron clouds around the atom stretch and deform in response to the force , but the electrons do not depart . glass , plastic , stone , and air are insulators . even for insulators , though , electric force can always be turned up high enough to rip electrons away—this is called breakdown . that 's what is happening to air molecules when you see a spark . semiconductor materials fall between insulators and conductors . they usually act like insulators , but we can make them act like conductors under certain circumstances . the most well-known semiconductor material is silicon ( atomic number $ 14 $ ) . our ability to finely control the insulating and conducting properties of silicon allows us to create modern marvels like computers and mobile phones . the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current . current is reported as the number of charges per unit time passing through a boundary . visualize placing a boundary all the way through a wire . station yourself near the boundary and count the number of charges passing by . report how much charge passed through the boundary in one second . we assign a positive sign to current corresponding to the direction a positive charge would be moving . since current is the amount of charge passing through a boundary in a fixed amount of time , it can be expressed mathematically using the following equation : $ i = \dfrac { dq } { dt } $ that 's current in a nutshell . a few remarks on current what carries current in metal ? since electrons are free to move about in metals , moving electrons are what makes up the current in metals . the positive nuclei in metal atoms are fixed in place and do not contribute to current . even though electrons have a negative charge and do almost all the work in most electric circuits , we still define a positive current as the direction a positive charge would move . this is a very old historical convention . can current be carried by positive charges ? yes . there are lots of examples . current is carried by both positive and negative charges in saltwater : if we put ordinary table salt in water , it becomes a good conductor . table salt is sodium chloride , nacl . the salt dissolves in water , into free-floating na $ ^+ $ and cl $ ^- $ ions . both ions respond to electric force and move through the saltwater solution , in opposite directions . in this case , the current is composed of moving atoms , both positive and negative ions , not just loose electrons . inside our bodies , electrical currents are moving ions , both positive and negative . the same definition of current works : count the number of charges passing by in a fixed amount of time . what causes current ? charged objects move in response to electric and magnetic forces . these forces come from electric and magnetic fields , which in turn come from the position and motion of other charges . what is the speed of current ? we do n't talk very often about the speed of current . answering the question , `` how fast is the current flowing ? '' requires understanding of a complex physical phenomenon and is not often relevant . current usually is n't about meters per second , it 's about charge per second . more often , we answer the question `` how much current is flowing ? '' all the time . how do we talk about current ? when discussing current , terms like through and in make a lot of sense . current flows through a resistor ; current flows in a wire . if you hear , `` the current across ... '' , it should sound odd . voltage to get our initial toehold on the concept of voltage , let 's look at an analogy : voltage resembles gravity for a mass $ m $ , a change of height $ h $ corresponds to a change in potential energy , $ \delta u = mg\delta h $ . for a charged particle $ q $ , a voltage $ v $ corresponds to a change in potential energy , $ \delta u = qv $ . voltage in an electric circuit is analogous to the product of $ g\cdot \delta h $ . where $ g $ is the acceleration due to gravity and $ \delta h $ is the change of height . a ball at the top of the hill rolls down . when it is halfway down , it has given up half of its potential energy . an electron at the top of a voltage `` hill '' travels `` downhill '' through wires and elements of a circuit . it gives up its potential energy , doing work along the way . when the electron is halfway down the hill , it has given up , or `` dropped '' , half of its potential energy . for both the ball and the electron , the trip down the hill happens spontaneously . the ball and electron move towards a lower energy state all by themselves . on the trip down , there can be things in the way of the ball , like trees or bears to bounce off . for electrons , we can guide electrons using wires and make them flow through electronic components —circuit design— and do interesting things along the way . we can express the voltage between two points mathematically as the change of energy experienced by a charge : $ v = \dfrac { \delta u } { q } $ that 's an intuitive description of voltage in a nutshell . power power is defined as the rate energy ( $ \text u $ ) is transformed or transferred over time . we measure power in units of joules/second , also known as watts . ( $ 1 \ , \text { watt } = 1\ , \text { joule } /\text { second } $ ) $ \text { power } = \dfrac { \text du } { \text dt } $ an electric circuit is capable of transferring power . current is the rate of flow of charge , and voltage measures the energy transferred per unit of charge . we can insert these definitions into the equation for power : $ \text { power } = \dfrac { \text du } { \text dt } = \dfrac { \text du } { \text dq } \cdot \dfrac { \text dq } { \text dt } = v \ , i $ electrical power is the product of voltage times current . in units of watts . summary these mental models for current and voltage will get us started on all sorts of interesting electric circuits . if you want to reach beyond this intuitive description of voltage you can read this more formal mathematical description of electric potential and voltage .
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when discussing current , terms like through and in make a lot of sense . current flows through a resistor ; current flows in a wire . if you hear , `` the current across ... '' , it should sound odd .
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when electrons passes through the resistor they losses 30 volt electrical potential energy , which means they have now 0 volts , so why we get current or shock then ?
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voltage and current are the cornerstone concepts in electricity . we will create our first mental models for these basic electrical quantities . we will also talk about power , which is what happens when voltage and current act together . charge the concept of electricity arises from an observation of nature . we observe a force between objects , that , like gravity , acts at a distance . the source of this force has been given the name charge . a very noticeable thing about electric force is that it is large , far greater than the force of gravity . unlike gravity , however , there are two types of electric charge . opposite types of charge attract , and like types of charge repel . gravity has only one type : it only attracts , never repels . conductors and insulators conductors are made of atoms whose outer , or valence , electrons have relatively weak bonds to their nuclei , as shown in this fanciful image of a copper atom . when a bunch of metal atoms are together , they gladly share their outer electrons with each other , creating a `` swarm '' of electrons not associated with a particular nucleus . a very small electric force can make the electron swarm move . copper , gold , silver , and aluminum are good conductors . so is saltwater . there are also poor conductors . tungsten—a metal used for light bulb filaments—and carbon—used in graphite form in pencils—are relatively poor conductors because their electrons are less prone to move . insulators are materials whose outer electrons are tightly bound to their nuclei . modest electric forces are not able to pull these electrons free . when an electric force is applied , the electron clouds around the atom stretch and deform in response to the force , but the electrons do not depart . glass , plastic , stone , and air are insulators . even for insulators , though , electric force can always be turned up high enough to rip electrons away—this is called breakdown . that 's what is happening to air molecules when you see a spark . semiconductor materials fall between insulators and conductors . they usually act like insulators , but we can make them act like conductors under certain circumstances . the most well-known semiconductor material is silicon ( atomic number $ 14 $ ) . our ability to finely control the insulating and conducting properties of silicon allows us to create modern marvels like computers and mobile phones . the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current . current is reported as the number of charges per unit time passing through a boundary . visualize placing a boundary all the way through a wire . station yourself near the boundary and count the number of charges passing by . report how much charge passed through the boundary in one second . we assign a positive sign to current corresponding to the direction a positive charge would be moving . since current is the amount of charge passing through a boundary in a fixed amount of time , it can be expressed mathematically using the following equation : $ i = \dfrac { dq } { dt } $ that 's current in a nutshell . a few remarks on current what carries current in metal ? since electrons are free to move about in metals , moving electrons are what makes up the current in metals . the positive nuclei in metal atoms are fixed in place and do not contribute to current . even though electrons have a negative charge and do almost all the work in most electric circuits , we still define a positive current as the direction a positive charge would move . this is a very old historical convention . can current be carried by positive charges ? yes . there are lots of examples . current is carried by both positive and negative charges in saltwater : if we put ordinary table salt in water , it becomes a good conductor . table salt is sodium chloride , nacl . the salt dissolves in water , into free-floating na $ ^+ $ and cl $ ^- $ ions . both ions respond to electric force and move through the saltwater solution , in opposite directions . in this case , the current is composed of moving atoms , both positive and negative ions , not just loose electrons . inside our bodies , electrical currents are moving ions , both positive and negative . the same definition of current works : count the number of charges passing by in a fixed amount of time . what causes current ? charged objects move in response to electric and magnetic forces . these forces come from electric and magnetic fields , which in turn come from the position and motion of other charges . what is the speed of current ? we do n't talk very often about the speed of current . answering the question , `` how fast is the current flowing ? '' requires understanding of a complex physical phenomenon and is not often relevant . current usually is n't about meters per second , it 's about charge per second . more often , we answer the question `` how much current is flowing ? '' all the time . how do we talk about current ? when discussing current , terms like through and in make a lot of sense . current flows through a resistor ; current flows in a wire . if you hear , `` the current across ... '' , it should sound odd . voltage to get our initial toehold on the concept of voltage , let 's look at an analogy : voltage resembles gravity for a mass $ m $ , a change of height $ h $ corresponds to a change in potential energy , $ \delta u = mg\delta h $ . for a charged particle $ q $ , a voltage $ v $ corresponds to a change in potential energy , $ \delta u = qv $ . voltage in an electric circuit is analogous to the product of $ g\cdot \delta h $ . where $ g $ is the acceleration due to gravity and $ \delta h $ is the change of height . a ball at the top of the hill rolls down . when it is halfway down , it has given up half of its potential energy . an electron at the top of a voltage `` hill '' travels `` downhill '' through wires and elements of a circuit . it gives up its potential energy , doing work along the way . when the electron is halfway down the hill , it has given up , or `` dropped '' , half of its potential energy . for both the ball and the electron , the trip down the hill happens spontaneously . the ball and electron move towards a lower energy state all by themselves . on the trip down , there can be things in the way of the ball , like trees or bears to bounce off . for electrons , we can guide electrons using wires and make them flow through electronic components —circuit design— and do interesting things along the way . we can express the voltage between two points mathematically as the change of energy experienced by a charge : $ v = \dfrac { \delta u } { q } $ that 's an intuitive description of voltage in a nutshell . power power is defined as the rate energy ( $ \text u $ ) is transformed or transferred over time . we measure power in units of joules/second , also known as watts . ( $ 1 \ , \text { watt } = 1\ , \text { joule } /\text { second } $ ) $ \text { power } = \dfrac { \text du } { \text dt } $ an electric circuit is capable of transferring power . current is the rate of flow of charge , and voltage measures the energy transferred per unit of charge . we can insert these definitions into the equation for power : $ \text { power } = \dfrac { \text du } { \text dt } = \dfrac { \text du } { \text dq } \cdot \dfrac { \text dq } { \text dt } = v \ , i $ electrical power is the product of voltage times current . in units of watts . summary these mental models for current and voltage will get us started on all sorts of interesting electric circuits . if you want to reach beyond this intuitive description of voltage you can read this more formal mathematical description of electric potential and voltage .
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they usually act like insulators , but we can make them act like conductors under certain circumstances . the most well-known semiconductor material is silicon ( atomic number $ 14 $ ) . our ability to finely control the insulating and conducting properties of silicon allows us to create modern marvels like computers and mobile phones .
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does the number of valence electrons directly correlate with the conductivity of the material ?
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voltage and current are the cornerstone concepts in electricity . we will create our first mental models for these basic electrical quantities . we will also talk about power , which is what happens when voltage and current act together . charge the concept of electricity arises from an observation of nature . we observe a force between objects , that , like gravity , acts at a distance . the source of this force has been given the name charge . a very noticeable thing about electric force is that it is large , far greater than the force of gravity . unlike gravity , however , there are two types of electric charge . opposite types of charge attract , and like types of charge repel . gravity has only one type : it only attracts , never repels . conductors and insulators conductors are made of atoms whose outer , or valence , electrons have relatively weak bonds to their nuclei , as shown in this fanciful image of a copper atom . when a bunch of metal atoms are together , they gladly share their outer electrons with each other , creating a `` swarm '' of electrons not associated with a particular nucleus . a very small electric force can make the electron swarm move . copper , gold , silver , and aluminum are good conductors . so is saltwater . there are also poor conductors . tungsten—a metal used for light bulb filaments—and carbon—used in graphite form in pencils—are relatively poor conductors because their electrons are less prone to move . insulators are materials whose outer electrons are tightly bound to their nuclei . modest electric forces are not able to pull these electrons free . when an electric force is applied , the electron clouds around the atom stretch and deform in response to the force , but the electrons do not depart . glass , plastic , stone , and air are insulators . even for insulators , though , electric force can always be turned up high enough to rip electrons away—this is called breakdown . that 's what is happening to air molecules when you see a spark . semiconductor materials fall between insulators and conductors . they usually act like insulators , but we can make them act like conductors under certain circumstances . the most well-known semiconductor material is silicon ( atomic number $ 14 $ ) . our ability to finely control the insulating and conducting properties of silicon allows us to create modern marvels like computers and mobile phones . the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current . current is reported as the number of charges per unit time passing through a boundary . visualize placing a boundary all the way through a wire . station yourself near the boundary and count the number of charges passing by . report how much charge passed through the boundary in one second . we assign a positive sign to current corresponding to the direction a positive charge would be moving . since current is the amount of charge passing through a boundary in a fixed amount of time , it can be expressed mathematically using the following equation : $ i = \dfrac { dq } { dt } $ that 's current in a nutshell . a few remarks on current what carries current in metal ? since electrons are free to move about in metals , moving electrons are what makes up the current in metals . the positive nuclei in metal atoms are fixed in place and do not contribute to current . even though electrons have a negative charge and do almost all the work in most electric circuits , we still define a positive current as the direction a positive charge would move . this is a very old historical convention . can current be carried by positive charges ? yes . there are lots of examples . current is carried by both positive and negative charges in saltwater : if we put ordinary table salt in water , it becomes a good conductor . table salt is sodium chloride , nacl . the salt dissolves in water , into free-floating na $ ^+ $ and cl $ ^- $ ions . both ions respond to electric force and move through the saltwater solution , in opposite directions . in this case , the current is composed of moving atoms , both positive and negative ions , not just loose electrons . inside our bodies , electrical currents are moving ions , both positive and negative . the same definition of current works : count the number of charges passing by in a fixed amount of time . what causes current ? charged objects move in response to electric and magnetic forces . these forces come from electric and magnetic fields , which in turn come from the position and motion of other charges . what is the speed of current ? we do n't talk very often about the speed of current . answering the question , `` how fast is the current flowing ? '' requires understanding of a complex physical phenomenon and is not often relevant . current usually is n't about meters per second , it 's about charge per second . more often , we answer the question `` how much current is flowing ? '' all the time . how do we talk about current ? when discussing current , terms like through and in make a lot of sense . current flows through a resistor ; current flows in a wire . if you hear , `` the current across ... '' , it should sound odd . voltage to get our initial toehold on the concept of voltage , let 's look at an analogy : voltage resembles gravity for a mass $ m $ , a change of height $ h $ corresponds to a change in potential energy , $ \delta u = mg\delta h $ . for a charged particle $ q $ , a voltage $ v $ corresponds to a change in potential energy , $ \delta u = qv $ . voltage in an electric circuit is analogous to the product of $ g\cdot \delta h $ . where $ g $ is the acceleration due to gravity and $ \delta h $ is the change of height . a ball at the top of the hill rolls down . when it is halfway down , it has given up half of its potential energy . an electron at the top of a voltage `` hill '' travels `` downhill '' through wires and elements of a circuit . it gives up its potential energy , doing work along the way . when the electron is halfway down the hill , it has given up , or `` dropped '' , half of its potential energy . for both the ball and the electron , the trip down the hill happens spontaneously . the ball and electron move towards a lower energy state all by themselves . on the trip down , there can be things in the way of the ball , like trees or bears to bounce off . for electrons , we can guide electrons using wires and make them flow through electronic components —circuit design— and do interesting things along the way . we can express the voltage between two points mathematically as the change of energy experienced by a charge : $ v = \dfrac { \delta u } { q } $ that 's an intuitive description of voltage in a nutshell . power power is defined as the rate energy ( $ \text u $ ) is transformed or transferred over time . we measure power in units of joules/second , also known as watts . ( $ 1 \ , \text { watt } = 1\ , \text { joule } /\text { second } $ ) $ \text { power } = \dfrac { \text du } { \text dt } $ an electric circuit is capable of transferring power . current is the rate of flow of charge , and voltage measures the energy transferred per unit of charge . we can insert these definitions into the equation for power : $ \text { power } = \dfrac { \text du } { \text dt } = \dfrac { \text du } { \text dq } \cdot \dfrac { \text dq } { \text dt } = v \ , i $ electrical power is the product of voltage times current . in units of watts . summary these mental models for current and voltage will get us started on all sorts of interesting electric circuits . if you want to reach beyond this intuitive description of voltage you can read this more formal mathematical description of electric potential and voltage .
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station yourself near the boundary and count the number of charges passing by . report how much charge passed through the boundary in one second . we assign a positive sign to current corresponding to the direction a positive charge would be moving .
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why we need at least one resistor to complete circuit ?
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voltage and current are the cornerstone concepts in electricity . we will create our first mental models for these basic electrical quantities . we will also talk about power , which is what happens when voltage and current act together . charge the concept of electricity arises from an observation of nature . we observe a force between objects , that , like gravity , acts at a distance . the source of this force has been given the name charge . a very noticeable thing about electric force is that it is large , far greater than the force of gravity . unlike gravity , however , there are two types of electric charge . opposite types of charge attract , and like types of charge repel . gravity has only one type : it only attracts , never repels . conductors and insulators conductors are made of atoms whose outer , or valence , electrons have relatively weak bonds to their nuclei , as shown in this fanciful image of a copper atom . when a bunch of metal atoms are together , they gladly share their outer electrons with each other , creating a `` swarm '' of electrons not associated with a particular nucleus . a very small electric force can make the electron swarm move . copper , gold , silver , and aluminum are good conductors . so is saltwater . there are also poor conductors . tungsten—a metal used for light bulb filaments—and carbon—used in graphite form in pencils—are relatively poor conductors because their electrons are less prone to move . insulators are materials whose outer electrons are tightly bound to their nuclei . modest electric forces are not able to pull these electrons free . when an electric force is applied , the electron clouds around the atom stretch and deform in response to the force , but the electrons do not depart . glass , plastic , stone , and air are insulators . even for insulators , though , electric force can always be turned up high enough to rip electrons away—this is called breakdown . that 's what is happening to air molecules when you see a spark . semiconductor materials fall between insulators and conductors . they usually act like insulators , but we can make them act like conductors under certain circumstances . the most well-known semiconductor material is silicon ( atomic number $ 14 $ ) . our ability to finely control the insulating and conducting properties of silicon allows us to create modern marvels like computers and mobile phones . the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current . current is reported as the number of charges per unit time passing through a boundary . visualize placing a boundary all the way through a wire . station yourself near the boundary and count the number of charges passing by . report how much charge passed through the boundary in one second . we assign a positive sign to current corresponding to the direction a positive charge would be moving . since current is the amount of charge passing through a boundary in a fixed amount of time , it can be expressed mathematically using the following equation : $ i = \dfrac { dq } { dt } $ that 's current in a nutshell . a few remarks on current what carries current in metal ? since electrons are free to move about in metals , moving electrons are what makes up the current in metals . the positive nuclei in metal atoms are fixed in place and do not contribute to current . even though electrons have a negative charge and do almost all the work in most electric circuits , we still define a positive current as the direction a positive charge would move . this is a very old historical convention . can current be carried by positive charges ? yes . there are lots of examples . current is carried by both positive and negative charges in saltwater : if we put ordinary table salt in water , it becomes a good conductor . table salt is sodium chloride , nacl . the salt dissolves in water , into free-floating na $ ^+ $ and cl $ ^- $ ions . both ions respond to electric force and move through the saltwater solution , in opposite directions . in this case , the current is composed of moving atoms , both positive and negative ions , not just loose electrons . inside our bodies , electrical currents are moving ions , both positive and negative . the same definition of current works : count the number of charges passing by in a fixed amount of time . what causes current ? charged objects move in response to electric and magnetic forces . these forces come from electric and magnetic fields , which in turn come from the position and motion of other charges . what is the speed of current ? we do n't talk very often about the speed of current . answering the question , `` how fast is the current flowing ? '' requires understanding of a complex physical phenomenon and is not often relevant . current usually is n't about meters per second , it 's about charge per second . more often , we answer the question `` how much current is flowing ? '' all the time . how do we talk about current ? when discussing current , terms like through and in make a lot of sense . current flows through a resistor ; current flows in a wire . if you hear , `` the current across ... '' , it should sound odd . voltage to get our initial toehold on the concept of voltage , let 's look at an analogy : voltage resembles gravity for a mass $ m $ , a change of height $ h $ corresponds to a change in potential energy , $ \delta u = mg\delta h $ . for a charged particle $ q $ , a voltage $ v $ corresponds to a change in potential energy , $ \delta u = qv $ . voltage in an electric circuit is analogous to the product of $ g\cdot \delta h $ . where $ g $ is the acceleration due to gravity and $ \delta h $ is the change of height . a ball at the top of the hill rolls down . when it is halfway down , it has given up half of its potential energy . an electron at the top of a voltage `` hill '' travels `` downhill '' through wires and elements of a circuit . it gives up its potential energy , doing work along the way . when the electron is halfway down the hill , it has given up , or `` dropped '' , half of its potential energy . for both the ball and the electron , the trip down the hill happens spontaneously . the ball and electron move towards a lower energy state all by themselves . on the trip down , there can be things in the way of the ball , like trees or bears to bounce off . for electrons , we can guide electrons using wires and make them flow through electronic components —circuit design— and do interesting things along the way . we can express the voltage between two points mathematically as the change of energy experienced by a charge : $ v = \dfrac { \delta u } { q } $ that 's an intuitive description of voltage in a nutshell . power power is defined as the rate energy ( $ \text u $ ) is transformed or transferred over time . we measure power in units of joules/second , also known as watts . ( $ 1 \ , \text { watt } = 1\ , \text { joule } /\text { second } $ ) $ \text { power } = \dfrac { \text du } { \text dt } $ an electric circuit is capable of transferring power . current is the rate of flow of charge , and voltage measures the energy transferred per unit of charge . we can insert these definitions into the equation for power : $ \text { power } = \dfrac { \text du } { \text dt } = \dfrac { \text du } { \text dq } \cdot \dfrac { \text dq } { \text dt } = v \ , i $ electrical power is the product of voltage times current . in units of watts . summary these mental models for current and voltage will get us started on all sorts of interesting electric circuits . if you want to reach beyond this intuitive description of voltage you can read this more formal mathematical description of electric potential and voltage .
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we will create our first mental models for these basic electrical quantities . we will also talk about power , which is what happens when voltage and current act together . charge the concept of electricity arises from an observation of nature .
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are power and voltage the same thing ?
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voltage and current are the cornerstone concepts in electricity . we will create our first mental models for these basic electrical quantities . we will also talk about power , which is what happens when voltage and current act together . charge the concept of electricity arises from an observation of nature . we observe a force between objects , that , like gravity , acts at a distance . the source of this force has been given the name charge . a very noticeable thing about electric force is that it is large , far greater than the force of gravity . unlike gravity , however , there are two types of electric charge . opposite types of charge attract , and like types of charge repel . gravity has only one type : it only attracts , never repels . conductors and insulators conductors are made of atoms whose outer , or valence , electrons have relatively weak bonds to their nuclei , as shown in this fanciful image of a copper atom . when a bunch of metal atoms are together , they gladly share their outer electrons with each other , creating a `` swarm '' of electrons not associated with a particular nucleus . a very small electric force can make the electron swarm move . copper , gold , silver , and aluminum are good conductors . so is saltwater . there are also poor conductors . tungsten—a metal used for light bulb filaments—and carbon—used in graphite form in pencils—are relatively poor conductors because their electrons are less prone to move . insulators are materials whose outer electrons are tightly bound to their nuclei . modest electric forces are not able to pull these electrons free . when an electric force is applied , the electron clouds around the atom stretch and deform in response to the force , but the electrons do not depart . glass , plastic , stone , and air are insulators . even for insulators , though , electric force can always be turned up high enough to rip electrons away—this is called breakdown . that 's what is happening to air molecules when you see a spark . semiconductor materials fall between insulators and conductors . they usually act like insulators , but we can make them act like conductors under certain circumstances . the most well-known semiconductor material is silicon ( atomic number $ 14 $ ) . our ability to finely control the insulating and conducting properties of silicon allows us to create modern marvels like computers and mobile phones . the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current . current is reported as the number of charges per unit time passing through a boundary . visualize placing a boundary all the way through a wire . station yourself near the boundary and count the number of charges passing by . report how much charge passed through the boundary in one second . we assign a positive sign to current corresponding to the direction a positive charge would be moving . since current is the amount of charge passing through a boundary in a fixed amount of time , it can be expressed mathematically using the following equation : $ i = \dfrac { dq } { dt } $ that 's current in a nutshell . a few remarks on current what carries current in metal ? since electrons are free to move about in metals , moving electrons are what makes up the current in metals . the positive nuclei in metal atoms are fixed in place and do not contribute to current . even though electrons have a negative charge and do almost all the work in most electric circuits , we still define a positive current as the direction a positive charge would move . this is a very old historical convention . can current be carried by positive charges ? yes . there are lots of examples . current is carried by both positive and negative charges in saltwater : if we put ordinary table salt in water , it becomes a good conductor . table salt is sodium chloride , nacl . the salt dissolves in water , into free-floating na $ ^+ $ and cl $ ^- $ ions . both ions respond to electric force and move through the saltwater solution , in opposite directions . in this case , the current is composed of moving atoms , both positive and negative ions , not just loose electrons . inside our bodies , electrical currents are moving ions , both positive and negative . the same definition of current works : count the number of charges passing by in a fixed amount of time . what causes current ? charged objects move in response to electric and magnetic forces . these forces come from electric and magnetic fields , which in turn come from the position and motion of other charges . what is the speed of current ? we do n't talk very often about the speed of current . answering the question , `` how fast is the current flowing ? '' requires understanding of a complex physical phenomenon and is not often relevant . current usually is n't about meters per second , it 's about charge per second . more often , we answer the question `` how much current is flowing ? '' all the time . how do we talk about current ? when discussing current , terms like through and in make a lot of sense . current flows through a resistor ; current flows in a wire . if you hear , `` the current across ... '' , it should sound odd . voltage to get our initial toehold on the concept of voltage , let 's look at an analogy : voltage resembles gravity for a mass $ m $ , a change of height $ h $ corresponds to a change in potential energy , $ \delta u = mg\delta h $ . for a charged particle $ q $ , a voltage $ v $ corresponds to a change in potential energy , $ \delta u = qv $ . voltage in an electric circuit is analogous to the product of $ g\cdot \delta h $ . where $ g $ is the acceleration due to gravity and $ \delta h $ is the change of height . a ball at the top of the hill rolls down . when it is halfway down , it has given up half of its potential energy . an electron at the top of a voltage `` hill '' travels `` downhill '' through wires and elements of a circuit . it gives up its potential energy , doing work along the way . when the electron is halfway down the hill , it has given up , or `` dropped '' , half of its potential energy . for both the ball and the electron , the trip down the hill happens spontaneously . the ball and electron move towards a lower energy state all by themselves . on the trip down , there can be things in the way of the ball , like trees or bears to bounce off . for electrons , we can guide electrons using wires and make them flow through electronic components —circuit design— and do interesting things along the way . we can express the voltage between two points mathematically as the change of energy experienced by a charge : $ v = \dfrac { \delta u } { q } $ that 's an intuitive description of voltage in a nutshell . power power is defined as the rate energy ( $ \text u $ ) is transformed or transferred over time . we measure power in units of joules/second , also known as watts . ( $ 1 \ , \text { watt } = 1\ , \text { joule } /\text { second } $ ) $ \text { power } = \dfrac { \text du } { \text dt } $ an electric circuit is capable of transferring power . current is the rate of flow of charge , and voltage measures the energy transferred per unit of charge . we can insert these definitions into the equation for power : $ \text { power } = \dfrac { \text du } { \text dt } = \dfrac { \text du } { \text dq } \cdot \dfrac { \text dq } { \text dt } = v \ , i $ electrical power is the product of voltage times current . in units of watts . summary these mental models for current and voltage will get us started on all sorts of interesting electric circuits . if you want to reach beyond this intuitive description of voltage you can read this more formal mathematical description of electric potential and voltage .
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the positive nuclei in metal atoms are fixed in place and do not contribute to current . even though electrons have a negative charge and do almost all the work in most electric circuits , we still define a positive current as the direction a positive charge would move . this is a very old historical convention .
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is there a reason why proton 's charge is called positive and electron 's charge is called negative ?
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voltage and current are the cornerstone concepts in electricity . we will create our first mental models for these basic electrical quantities . we will also talk about power , which is what happens when voltage and current act together . charge the concept of electricity arises from an observation of nature . we observe a force between objects , that , like gravity , acts at a distance . the source of this force has been given the name charge . a very noticeable thing about electric force is that it is large , far greater than the force of gravity . unlike gravity , however , there are two types of electric charge . opposite types of charge attract , and like types of charge repel . gravity has only one type : it only attracts , never repels . conductors and insulators conductors are made of atoms whose outer , or valence , electrons have relatively weak bonds to their nuclei , as shown in this fanciful image of a copper atom . when a bunch of metal atoms are together , they gladly share their outer electrons with each other , creating a `` swarm '' of electrons not associated with a particular nucleus . a very small electric force can make the electron swarm move . copper , gold , silver , and aluminum are good conductors . so is saltwater . there are also poor conductors . tungsten—a metal used for light bulb filaments—and carbon—used in graphite form in pencils—are relatively poor conductors because their electrons are less prone to move . insulators are materials whose outer electrons are tightly bound to their nuclei . modest electric forces are not able to pull these electrons free . when an electric force is applied , the electron clouds around the atom stretch and deform in response to the force , but the electrons do not depart . glass , plastic , stone , and air are insulators . even for insulators , though , electric force can always be turned up high enough to rip electrons away—this is called breakdown . that 's what is happening to air molecules when you see a spark . semiconductor materials fall between insulators and conductors . they usually act like insulators , but we can make them act like conductors under certain circumstances . the most well-known semiconductor material is silicon ( atomic number $ 14 $ ) . our ability to finely control the insulating and conducting properties of silicon allows us to create modern marvels like computers and mobile phones . the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current . current is reported as the number of charges per unit time passing through a boundary . visualize placing a boundary all the way through a wire . station yourself near the boundary and count the number of charges passing by . report how much charge passed through the boundary in one second . we assign a positive sign to current corresponding to the direction a positive charge would be moving . since current is the amount of charge passing through a boundary in a fixed amount of time , it can be expressed mathematically using the following equation : $ i = \dfrac { dq } { dt } $ that 's current in a nutshell . a few remarks on current what carries current in metal ? since electrons are free to move about in metals , moving electrons are what makes up the current in metals . the positive nuclei in metal atoms are fixed in place and do not contribute to current . even though electrons have a negative charge and do almost all the work in most electric circuits , we still define a positive current as the direction a positive charge would move . this is a very old historical convention . can current be carried by positive charges ? yes . there are lots of examples . current is carried by both positive and negative charges in saltwater : if we put ordinary table salt in water , it becomes a good conductor . table salt is sodium chloride , nacl . the salt dissolves in water , into free-floating na $ ^+ $ and cl $ ^- $ ions . both ions respond to electric force and move through the saltwater solution , in opposite directions . in this case , the current is composed of moving atoms , both positive and negative ions , not just loose electrons . inside our bodies , electrical currents are moving ions , both positive and negative . the same definition of current works : count the number of charges passing by in a fixed amount of time . what causes current ? charged objects move in response to electric and magnetic forces . these forces come from electric and magnetic fields , which in turn come from the position and motion of other charges . what is the speed of current ? we do n't talk very often about the speed of current . answering the question , `` how fast is the current flowing ? '' requires understanding of a complex physical phenomenon and is not often relevant . current usually is n't about meters per second , it 's about charge per second . more often , we answer the question `` how much current is flowing ? '' all the time . how do we talk about current ? when discussing current , terms like through and in make a lot of sense . current flows through a resistor ; current flows in a wire . if you hear , `` the current across ... '' , it should sound odd . voltage to get our initial toehold on the concept of voltage , let 's look at an analogy : voltage resembles gravity for a mass $ m $ , a change of height $ h $ corresponds to a change in potential energy , $ \delta u = mg\delta h $ . for a charged particle $ q $ , a voltage $ v $ corresponds to a change in potential energy , $ \delta u = qv $ . voltage in an electric circuit is analogous to the product of $ g\cdot \delta h $ . where $ g $ is the acceleration due to gravity and $ \delta h $ is the change of height . a ball at the top of the hill rolls down . when it is halfway down , it has given up half of its potential energy . an electron at the top of a voltage `` hill '' travels `` downhill '' through wires and elements of a circuit . it gives up its potential energy , doing work along the way . when the electron is halfway down the hill , it has given up , or `` dropped '' , half of its potential energy . for both the ball and the electron , the trip down the hill happens spontaneously . the ball and electron move towards a lower energy state all by themselves . on the trip down , there can be things in the way of the ball , like trees or bears to bounce off . for electrons , we can guide electrons using wires and make them flow through electronic components —circuit design— and do interesting things along the way . we can express the voltage between two points mathematically as the change of energy experienced by a charge : $ v = \dfrac { \delta u } { q } $ that 's an intuitive description of voltage in a nutshell . power power is defined as the rate energy ( $ \text u $ ) is transformed or transferred over time . we measure power in units of joules/second , also known as watts . ( $ 1 \ , \text { watt } = 1\ , \text { joule } /\text { second } $ ) $ \text { power } = \dfrac { \text du } { \text dt } $ an electric circuit is capable of transferring power . current is the rate of flow of charge , and voltage measures the energy transferred per unit of charge . we can insert these definitions into the equation for power : $ \text { power } = \dfrac { \text du } { \text dt } = \dfrac { \text du } { \text dq } \cdot \dfrac { \text dq } { \text dt } = v \ , i $ electrical power is the product of voltage times current . in units of watts . summary these mental models for current and voltage will get us started on all sorts of interesting electric circuits . if you want to reach beyond this intuitive description of voltage you can read this more formal mathematical description of electric potential and voltage .
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current is the rate of flow of charge , and voltage measures the energy transferred per unit of charge . we can insert these definitions into the equation for power : $ \text { power } = \dfrac { \text du } { \text dt } = \dfrac { \text du } { \text dq } \cdot \dfrac { \text dq } { \text dt } = v \ , i $ electrical power is the product of voltage times current . in units of watts .
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question : in i=dq/dt , what does the i , q , & t mean ?
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voltage and current are the cornerstone concepts in electricity . we will create our first mental models for these basic electrical quantities . we will also talk about power , which is what happens when voltage and current act together . charge the concept of electricity arises from an observation of nature . we observe a force between objects , that , like gravity , acts at a distance . the source of this force has been given the name charge . a very noticeable thing about electric force is that it is large , far greater than the force of gravity . unlike gravity , however , there are two types of electric charge . opposite types of charge attract , and like types of charge repel . gravity has only one type : it only attracts , never repels . conductors and insulators conductors are made of atoms whose outer , or valence , electrons have relatively weak bonds to their nuclei , as shown in this fanciful image of a copper atom . when a bunch of metal atoms are together , they gladly share their outer electrons with each other , creating a `` swarm '' of electrons not associated with a particular nucleus . a very small electric force can make the electron swarm move . copper , gold , silver , and aluminum are good conductors . so is saltwater . there are also poor conductors . tungsten—a metal used for light bulb filaments—and carbon—used in graphite form in pencils—are relatively poor conductors because their electrons are less prone to move . insulators are materials whose outer electrons are tightly bound to their nuclei . modest electric forces are not able to pull these electrons free . when an electric force is applied , the electron clouds around the atom stretch and deform in response to the force , but the electrons do not depart . glass , plastic , stone , and air are insulators . even for insulators , though , electric force can always be turned up high enough to rip electrons away—this is called breakdown . that 's what is happening to air molecules when you see a spark . semiconductor materials fall between insulators and conductors . they usually act like insulators , but we can make them act like conductors under certain circumstances . the most well-known semiconductor material is silicon ( atomic number $ 14 $ ) . our ability to finely control the insulating and conducting properties of silicon allows us to create modern marvels like computers and mobile phones . the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current . current is reported as the number of charges per unit time passing through a boundary . visualize placing a boundary all the way through a wire . station yourself near the boundary and count the number of charges passing by . report how much charge passed through the boundary in one second . we assign a positive sign to current corresponding to the direction a positive charge would be moving . since current is the amount of charge passing through a boundary in a fixed amount of time , it can be expressed mathematically using the following equation : $ i = \dfrac { dq } { dt } $ that 's current in a nutshell . a few remarks on current what carries current in metal ? since electrons are free to move about in metals , moving electrons are what makes up the current in metals . the positive nuclei in metal atoms are fixed in place and do not contribute to current . even though electrons have a negative charge and do almost all the work in most electric circuits , we still define a positive current as the direction a positive charge would move . this is a very old historical convention . can current be carried by positive charges ? yes . there are lots of examples . current is carried by both positive and negative charges in saltwater : if we put ordinary table salt in water , it becomes a good conductor . table salt is sodium chloride , nacl . the salt dissolves in water , into free-floating na $ ^+ $ and cl $ ^- $ ions . both ions respond to electric force and move through the saltwater solution , in opposite directions . in this case , the current is composed of moving atoms , both positive and negative ions , not just loose electrons . inside our bodies , electrical currents are moving ions , both positive and negative . the same definition of current works : count the number of charges passing by in a fixed amount of time . what causes current ? charged objects move in response to electric and magnetic forces . these forces come from electric and magnetic fields , which in turn come from the position and motion of other charges . what is the speed of current ? we do n't talk very often about the speed of current . answering the question , `` how fast is the current flowing ? '' requires understanding of a complex physical phenomenon and is not often relevant . current usually is n't about meters per second , it 's about charge per second . more often , we answer the question `` how much current is flowing ? '' all the time . how do we talk about current ? when discussing current , terms like through and in make a lot of sense . current flows through a resistor ; current flows in a wire . if you hear , `` the current across ... '' , it should sound odd . voltage to get our initial toehold on the concept of voltage , let 's look at an analogy : voltage resembles gravity for a mass $ m $ , a change of height $ h $ corresponds to a change in potential energy , $ \delta u = mg\delta h $ . for a charged particle $ q $ , a voltage $ v $ corresponds to a change in potential energy , $ \delta u = qv $ . voltage in an electric circuit is analogous to the product of $ g\cdot \delta h $ . where $ g $ is the acceleration due to gravity and $ \delta h $ is the change of height . a ball at the top of the hill rolls down . when it is halfway down , it has given up half of its potential energy . an electron at the top of a voltage `` hill '' travels `` downhill '' through wires and elements of a circuit . it gives up its potential energy , doing work along the way . when the electron is halfway down the hill , it has given up , or `` dropped '' , half of its potential energy . for both the ball and the electron , the trip down the hill happens spontaneously . the ball and electron move towards a lower energy state all by themselves . on the trip down , there can be things in the way of the ball , like trees or bears to bounce off . for electrons , we can guide electrons using wires and make them flow through electronic components —circuit design— and do interesting things along the way . we can express the voltage between two points mathematically as the change of energy experienced by a charge : $ v = \dfrac { \delta u } { q } $ that 's an intuitive description of voltage in a nutshell . power power is defined as the rate energy ( $ \text u $ ) is transformed or transferred over time . we measure power in units of joules/second , also known as watts . ( $ 1 \ , \text { watt } = 1\ , \text { joule } /\text { second } $ ) $ \text { power } = \dfrac { \text du } { \text dt } $ an electric circuit is capable of transferring power . current is the rate of flow of charge , and voltage measures the energy transferred per unit of charge . we can insert these definitions into the equation for power : $ \text { power } = \dfrac { \text du } { \text dt } = \dfrac { \text du } { \text dq } \cdot \dfrac { \text dq } { \text dt } = v \ , i $ electrical power is the product of voltage times current . in units of watts . summary these mental models for current and voltage will get us started on all sorts of interesting electric circuits . if you want to reach beyond this intuitive description of voltage you can read this more formal mathematical description of electric potential and voltage .
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in this case , the current is composed of moving atoms , both positive and negative ions , not just loose electrons . inside our bodies , electrical currents are moving ions , both positive and negative . the same definition of current works : count the number of charges passing by in a fixed amount of time .
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what is inside these resistors ?
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voltage and current are the cornerstone concepts in electricity . we will create our first mental models for these basic electrical quantities . we will also talk about power , which is what happens when voltage and current act together . charge the concept of electricity arises from an observation of nature . we observe a force between objects , that , like gravity , acts at a distance . the source of this force has been given the name charge . a very noticeable thing about electric force is that it is large , far greater than the force of gravity . unlike gravity , however , there are two types of electric charge . opposite types of charge attract , and like types of charge repel . gravity has only one type : it only attracts , never repels . conductors and insulators conductors are made of atoms whose outer , or valence , electrons have relatively weak bonds to their nuclei , as shown in this fanciful image of a copper atom . when a bunch of metal atoms are together , they gladly share their outer electrons with each other , creating a `` swarm '' of electrons not associated with a particular nucleus . a very small electric force can make the electron swarm move . copper , gold , silver , and aluminum are good conductors . so is saltwater . there are also poor conductors . tungsten—a metal used for light bulb filaments—and carbon—used in graphite form in pencils—are relatively poor conductors because their electrons are less prone to move . insulators are materials whose outer electrons are tightly bound to their nuclei . modest electric forces are not able to pull these electrons free . when an electric force is applied , the electron clouds around the atom stretch and deform in response to the force , but the electrons do not depart . glass , plastic , stone , and air are insulators . even for insulators , though , electric force can always be turned up high enough to rip electrons away—this is called breakdown . that 's what is happening to air molecules when you see a spark . semiconductor materials fall between insulators and conductors . they usually act like insulators , but we can make them act like conductors under certain circumstances . the most well-known semiconductor material is silicon ( atomic number $ 14 $ ) . our ability to finely control the insulating and conducting properties of silicon allows us to create modern marvels like computers and mobile phones . the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current . current is reported as the number of charges per unit time passing through a boundary . visualize placing a boundary all the way through a wire . station yourself near the boundary and count the number of charges passing by . report how much charge passed through the boundary in one second . we assign a positive sign to current corresponding to the direction a positive charge would be moving . since current is the amount of charge passing through a boundary in a fixed amount of time , it can be expressed mathematically using the following equation : $ i = \dfrac { dq } { dt } $ that 's current in a nutshell . a few remarks on current what carries current in metal ? since electrons are free to move about in metals , moving electrons are what makes up the current in metals . the positive nuclei in metal atoms are fixed in place and do not contribute to current . even though electrons have a negative charge and do almost all the work in most electric circuits , we still define a positive current as the direction a positive charge would move . this is a very old historical convention . can current be carried by positive charges ? yes . there are lots of examples . current is carried by both positive and negative charges in saltwater : if we put ordinary table salt in water , it becomes a good conductor . table salt is sodium chloride , nacl . the salt dissolves in water , into free-floating na $ ^+ $ and cl $ ^- $ ions . both ions respond to electric force and move through the saltwater solution , in opposite directions . in this case , the current is composed of moving atoms , both positive and negative ions , not just loose electrons . inside our bodies , electrical currents are moving ions , both positive and negative . the same definition of current works : count the number of charges passing by in a fixed amount of time . what causes current ? charged objects move in response to electric and magnetic forces . these forces come from electric and magnetic fields , which in turn come from the position and motion of other charges . what is the speed of current ? we do n't talk very often about the speed of current . answering the question , `` how fast is the current flowing ? '' requires understanding of a complex physical phenomenon and is not often relevant . current usually is n't about meters per second , it 's about charge per second . more often , we answer the question `` how much current is flowing ? '' all the time . how do we talk about current ? when discussing current , terms like through and in make a lot of sense . current flows through a resistor ; current flows in a wire . if you hear , `` the current across ... '' , it should sound odd . voltage to get our initial toehold on the concept of voltage , let 's look at an analogy : voltage resembles gravity for a mass $ m $ , a change of height $ h $ corresponds to a change in potential energy , $ \delta u = mg\delta h $ . for a charged particle $ q $ , a voltage $ v $ corresponds to a change in potential energy , $ \delta u = qv $ . voltage in an electric circuit is analogous to the product of $ g\cdot \delta h $ . where $ g $ is the acceleration due to gravity and $ \delta h $ is the change of height . a ball at the top of the hill rolls down . when it is halfway down , it has given up half of its potential energy . an electron at the top of a voltage `` hill '' travels `` downhill '' through wires and elements of a circuit . it gives up its potential energy , doing work along the way . when the electron is halfway down the hill , it has given up , or `` dropped '' , half of its potential energy . for both the ball and the electron , the trip down the hill happens spontaneously . the ball and electron move towards a lower energy state all by themselves . on the trip down , there can be things in the way of the ball , like trees or bears to bounce off . for electrons , we can guide electrons using wires and make them flow through electronic components —circuit design— and do interesting things along the way . we can express the voltage between two points mathematically as the change of energy experienced by a charge : $ v = \dfrac { \delta u } { q } $ that 's an intuitive description of voltage in a nutshell . power power is defined as the rate energy ( $ \text u $ ) is transformed or transferred over time . we measure power in units of joules/second , also known as watts . ( $ 1 \ , \text { watt } = 1\ , \text { joule } /\text { second } $ ) $ \text { power } = \dfrac { \text du } { \text dt } $ an electric circuit is capable of transferring power . current is the rate of flow of charge , and voltage measures the energy transferred per unit of charge . we can insert these definitions into the equation for power : $ \text { power } = \dfrac { \text du } { \text dt } = \dfrac { \text du } { \text dq } \cdot \dfrac { \text dq } { \text dt } = v \ , i $ electrical power is the product of voltage times current . in units of watts . summary these mental models for current and voltage will get us started on all sorts of interesting electric circuits . if you want to reach beyond this intuitive description of voltage you can read this more formal mathematical description of electric potential and voltage .
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the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current .
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why it is difficult to measure the rate of change of current ?
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voltage and current are the cornerstone concepts in electricity . we will create our first mental models for these basic electrical quantities . we will also talk about power , which is what happens when voltage and current act together . charge the concept of electricity arises from an observation of nature . we observe a force between objects , that , like gravity , acts at a distance . the source of this force has been given the name charge . a very noticeable thing about electric force is that it is large , far greater than the force of gravity . unlike gravity , however , there are two types of electric charge . opposite types of charge attract , and like types of charge repel . gravity has only one type : it only attracts , never repels . conductors and insulators conductors are made of atoms whose outer , or valence , electrons have relatively weak bonds to their nuclei , as shown in this fanciful image of a copper atom . when a bunch of metal atoms are together , they gladly share their outer electrons with each other , creating a `` swarm '' of electrons not associated with a particular nucleus . a very small electric force can make the electron swarm move . copper , gold , silver , and aluminum are good conductors . so is saltwater . there are also poor conductors . tungsten—a metal used for light bulb filaments—and carbon—used in graphite form in pencils—are relatively poor conductors because their electrons are less prone to move . insulators are materials whose outer electrons are tightly bound to their nuclei . modest electric forces are not able to pull these electrons free . when an electric force is applied , the electron clouds around the atom stretch and deform in response to the force , but the electrons do not depart . glass , plastic , stone , and air are insulators . even for insulators , though , electric force can always be turned up high enough to rip electrons away—this is called breakdown . that 's what is happening to air molecules when you see a spark . semiconductor materials fall between insulators and conductors . they usually act like insulators , but we can make them act like conductors under certain circumstances . the most well-known semiconductor material is silicon ( atomic number $ 14 $ ) . our ability to finely control the insulating and conducting properties of silicon allows us to create modern marvels like computers and mobile phones . the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current . current is reported as the number of charges per unit time passing through a boundary . visualize placing a boundary all the way through a wire . station yourself near the boundary and count the number of charges passing by . report how much charge passed through the boundary in one second . we assign a positive sign to current corresponding to the direction a positive charge would be moving . since current is the amount of charge passing through a boundary in a fixed amount of time , it can be expressed mathematically using the following equation : $ i = \dfrac { dq } { dt } $ that 's current in a nutshell . a few remarks on current what carries current in metal ? since electrons are free to move about in metals , moving electrons are what makes up the current in metals . the positive nuclei in metal atoms are fixed in place and do not contribute to current . even though electrons have a negative charge and do almost all the work in most electric circuits , we still define a positive current as the direction a positive charge would move . this is a very old historical convention . can current be carried by positive charges ? yes . there are lots of examples . current is carried by both positive and negative charges in saltwater : if we put ordinary table salt in water , it becomes a good conductor . table salt is sodium chloride , nacl . the salt dissolves in water , into free-floating na $ ^+ $ and cl $ ^- $ ions . both ions respond to electric force and move through the saltwater solution , in opposite directions . in this case , the current is composed of moving atoms , both positive and negative ions , not just loose electrons . inside our bodies , electrical currents are moving ions , both positive and negative . the same definition of current works : count the number of charges passing by in a fixed amount of time . what causes current ? charged objects move in response to electric and magnetic forces . these forces come from electric and magnetic fields , which in turn come from the position and motion of other charges . what is the speed of current ? we do n't talk very often about the speed of current . answering the question , `` how fast is the current flowing ? '' requires understanding of a complex physical phenomenon and is not often relevant . current usually is n't about meters per second , it 's about charge per second . more often , we answer the question `` how much current is flowing ? '' all the time . how do we talk about current ? when discussing current , terms like through and in make a lot of sense . current flows through a resistor ; current flows in a wire . if you hear , `` the current across ... '' , it should sound odd . voltage to get our initial toehold on the concept of voltage , let 's look at an analogy : voltage resembles gravity for a mass $ m $ , a change of height $ h $ corresponds to a change in potential energy , $ \delta u = mg\delta h $ . for a charged particle $ q $ , a voltage $ v $ corresponds to a change in potential energy , $ \delta u = qv $ . voltage in an electric circuit is analogous to the product of $ g\cdot \delta h $ . where $ g $ is the acceleration due to gravity and $ \delta h $ is the change of height . a ball at the top of the hill rolls down . when it is halfway down , it has given up half of its potential energy . an electron at the top of a voltage `` hill '' travels `` downhill '' through wires and elements of a circuit . it gives up its potential energy , doing work along the way . when the electron is halfway down the hill , it has given up , or `` dropped '' , half of its potential energy . for both the ball and the electron , the trip down the hill happens spontaneously . the ball and electron move towards a lower energy state all by themselves . on the trip down , there can be things in the way of the ball , like trees or bears to bounce off . for electrons , we can guide electrons using wires and make them flow through electronic components —circuit design— and do interesting things along the way . we can express the voltage between two points mathematically as the change of energy experienced by a charge : $ v = \dfrac { \delta u } { q } $ that 's an intuitive description of voltage in a nutshell . power power is defined as the rate energy ( $ \text u $ ) is transformed or transferred over time . we measure power in units of joules/second , also known as watts . ( $ 1 \ , \text { watt } = 1\ , \text { joule } /\text { second } $ ) $ \text { power } = \dfrac { \text du } { \text dt } $ an electric circuit is capable of transferring power . current is the rate of flow of charge , and voltage measures the energy transferred per unit of charge . we can insert these definitions into the equation for power : $ \text { power } = \dfrac { \text du } { \text dt } = \dfrac { \text du } { \text dq } \cdot \dfrac { \text dq } { \text dt } = v \ , i $ electrical power is the product of voltage times current . in units of watts . summary these mental models for current and voltage will get us started on all sorts of interesting electric circuits . if you want to reach beyond this intuitive description of voltage you can read this more formal mathematical description of electric potential and voltage .
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these forces come from electric and magnetic fields , which in turn come from the position and motion of other charges . what is the speed of current ? we do n't talk very often about the speed of current .
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about the topic discussed above `` what is the speed of current ?
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voltage and current are the cornerstone concepts in electricity . we will create our first mental models for these basic electrical quantities . we will also talk about power , which is what happens when voltage and current act together . charge the concept of electricity arises from an observation of nature . we observe a force between objects , that , like gravity , acts at a distance . the source of this force has been given the name charge . a very noticeable thing about electric force is that it is large , far greater than the force of gravity . unlike gravity , however , there are two types of electric charge . opposite types of charge attract , and like types of charge repel . gravity has only one type : it only attracts , never repels . conductors and insulators conductors are made of atoms whose outer , or valence , electrons have relatively weak bonds to their nuclei , as shown in this fanciful image of a copper atom . when a bunch of metal atoms are together , they gladly share their outer electrons with each other , creating a `` swarm '' of electrons not associated with a particular nucleus . a very small electric force can make the electron swarm move . copper , gold , silver , and aluminum are good conductors . so is saltwater . there are also poor conductors . tungsten—a metal used for light bulb filaments—and carbon—used in graphite form in pencils—are relatively poor conductors because their electrons are less prone to move . insulators are materials whose outer electrons are tightly bound to their nuclei . modest electric forces are not able to pull these electrons free . when an electric force is applied , the electron clouds around the atom stretch and deform in response to the force , but the electrons do not depart . glass , plastic , stone , and air are insulators . even for insulators , though , electric force can always be turned up high enough to rip electrons away—this is called breakdown . that 's what is happening to air molecules when you see a spark . semiconductor materials fall between insulators and conductors . they usually act like insulators , but we can make them act like conductors under certain circumstances . the most well-known semiconductor material is silicon ( atomic number $ 14 $ ) . our ability to finely control the insulating and conducting properties of silicon allows us to create modern marvels like computers and mobile phones . the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current . current is reported as the number of charges per unit time passing through a boundary . visualize placing a boundary all the way through a wire . station yourself near the boundary and count the number of charges passing by . report how much charge passed through the boundary in one second . we assign a positive sign to current corresponding to the direction a positive charge would be moving . since current is the amount of charge passing through a boundary in a fixed amount of time , it can be expressed mathematically using the following equation : $ i = \dfrac { dq } { dt } $ that 's current in a nutshell . a few remarks on current what carries current in metal ? since electrons are free to move about in metals , moving electrons are what makes up the current in metals . the positive nuclei in metal atoms are fixed in place and do not contribute to current . even though electrons have a negative charge and do almost all the work in most electric circuits , we still define a positive current as the direction a positive charge would move . this is a very old historical convention . can current be carried by positive charges ? yes . there are lots of examples . current is carried by both positive and negative charges in saltwater : if we put ordinary table salt in water , it becomes a good conductor . table salt is sodium chloride , nacl . the salt dissolves in water , into free-floating na $ ^+ $ and cl $ ^- $ ions . both ions respond to electric force and move through the saltwater solution , in opposite directions . in this case , the current is composed of moving atoms , both positive and negative ions , not just loose electrons . inside our bodies , electrical currents are moving ions , both positive and negative . the same definition of current works : count the number of charges passing by in a fixed amount of time . what causes current ? charged objects move in response to electric and magnetic forces . these forces come from electric and magnetic fields , which in turn come from the position and motion of other charges . what is the speed of current ? we do n't talk very often about the speed of current . answering the question , `` how fast is the current flowing ? '' requires understanding of a complex physical phenomenon and is not often relevant . current usually is n't about meters per second , it 's about charge per second . more often , we answer the question `` how much current is flowing ? '' all the time . how do we talk about current ? when discussing current , terms like through and in make a lot of sense . current flows through a resistor ; current flows in a wire . if you hear , `` the current across ... '' , it should sound odd . voltage to get our initial toehold on the concept of voltage , let 's look at an analogy : voltage resembles gravity for a mass $ m $ , a change of height $ h $ corresponds to a change in potential energy , $ \delta u = mg\delta h $ . for a charged particle $ q $ , a voltage $ v $ corresponds to a change in potential energy , $ \delta u = qv $ . voltage in an electric circuit is analogous to the product of $ g\cdot \delta h $ . where $ g $ is the acceleration due to gravity and $ \delta h $ is the change of height . a ball at the top of the hill rolls down . when it is halfway down , it has given up half of its potential energy . an electron at the top of a voltage `` hill '' travels `` downhill '' through wires and elements of a circuit . it gives up its potential energy , doing work along the way . when the electron is halfway down the hill , it has given up , or `` dropped '' , half of its potential energy . for both the ball and the electron , the trip down the hill happens spontaneously . the ball and electron move towards a lower energy state all by themselves . on the trip down , there can be things in the way of the ball , like trees or bears to bounce off . for electrons , we can guide electrons using wires and make them flow through electronic components —circuit design— and do interesting things along the way . we can express the voltage between two points mathematically as the change of energy experienced by a charge : $ v = \dfrac { \delta u } { q } $ that 's an intuitive description of voltage in a nutshell . power power is defined as the rate energy ( $ \text u $ ) is transformed or transferred over time . we measure power in units of joules/second , also known as watts . ( $ 1 \ , \text { watt } = 1\ , \text { joule } /\text { second } $ ) $ \text { power } = \dfrac { \text du } { \text dt } $ an electric circuit is capable of transferring power . current is the rate of flow of charge , and voltage measures the energy transferred per unit of charge . we can insert these definitions into the equation for power : $ \text { power } = \dfrac { \text du } { \text dt } = \dfrac { \text du } { \text dq } \cdot \dfrac { \text dq } { \text dt } = v \ , i $ electrical power is the product of voltage times current . in units of watts . summary these mental models for current and voltage will get us started on all sorts of interesting electric circuits . if you want to reach beyond this intuitive description of voltage you can read this more formal mathematical description of electric potential and voltage .
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requires understanding of a complex physical phenomenon and is not often relevant . current usually is n't about meters per second , it 's about charge per second . more often , we answer the question `` how much current is flowing ? ''
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`` , if current is charge per second , ca n't we know , given a certain distance ( d ) of wire and seeing how long a certain amount of charge takes to move that distance calculate the velocity of each individual charge ?
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voltage and current are the cornerstone concepts in electricity . we will create our first mental models for these basic electrical quantities . we will also talk about power , which is what happens when voltage and current act together . charge the concept of electricity arises from an observation of nature . we observe a force between objects , that , like gravity , acts at a distance . the source of this force has been given the name charge . a very noticeable thing about electric force is that it is large , far greater than the force of gravity . unlike gravity , however , there are two types of electric charge . opposite types of charge attract , and like types of charge repel . gravity has only one type : it only attracts , never repels . conductors and insulators conductors are made of atoms whose outer , or valence , electrons have relatively weak bonds to their nuclei , as shown in this fanciful image of a copper atom . when a bunch of metal atoms are together , they gladly share their outer electrons with each other , creating a `` swarm '' of electrons not associated with a particular nucleus . a very small electric force can make the electron swarm move . copper , gold , silver , and aluminum are good conductors . so is saltwater . there are also poor conductors . tungsten—a metal used for light bulb filaments—and carbon—used in graphite form in pencils—are relatively poor conductors because their electrons are less prone to move . insulators are materials whose outer electrons are tightly bound to their nuclei . modest electric forces are not able to pull these electrons free . when an electric force is applied , the electron clouds around the atom stretch and deform in response to the force , but the electrons do not depart . glass , plastic , stone , and air are insulators . even for insulators , though , electric force can always be turned up high enough to rip electrons away—this is called breakdown . that 's what is happening to air molecules when you see a spark . semiconductor materials fall between insulators and conductors . they usually act like insulators , but we can make them act like conductors under certain circumstances . the most well-known semiconductor material is silicon ( atomic number $ 14 $ ) . our ability to finely control the insulating and conducting properties of silicon allows us to create modern marvels like computers and mobile phones . the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current . current is reported as the number of charges per unit time passing through a boundary . visualize placing a boundary all the way through a wire . station yourself near the boundary and count the number of charges passing by . report how much charge passed through the boundary in one second . we assign a positive sign to current corresponding to the direction a positive charge would be moving . since current is the amount of charge passing through a boundary in a fixed amount of time , it can be expressed mathematically using the following equation : $ i = \dfrac { dq } { dt } $ that 's current in a nutshell . a few remarks on current what carries current in metal ? since electrons are free to move about in metals , moving electrons are what makes up the current in metals . the positive nuclei in metal atoms are fixed in place and do not contribute to current . even though electrons have a negative charge and do almost all the work in most electric circuits , we still define a positive current as the direction a positive charge would move . this is a very old historical convention . can current be carried by positive charges ? yes . there are lots of examples . current is carried by both positive and negative charges in saltwater : if we put ordinary table salt in water , it becomes a good conductor . table salt is sodium chloride , nacl . the salt dissolves in water , into free-floating na $ ^+ $ and cl $ ^- $ ions . both ions respond to electric force and move through the saltwater solution , in opposite directions . in this case , the current is composed of moving atoms , both positive and negative ions , not just loose electrons . inside our bodies , electrical currents are moving ions , both positive and negative . the same definition of current works : count the number of charges passing by in a fixed amount of time . what causes current ? charged objects move in response to electric and magnetic forces . these forces come from electric and magnetic fields , which in turn come from the position and motion of other charges . what is the speed of current ? we do n't talk very often about the speed of current . answering the question , `` how fast is the current flowing ? '' requires understanding of a complex physical phenomenon and is not often relevant . current usually is n't about meters per second , it 's about charge per second . more often , we answer the question `` how much current is flowing ? '' all the time . how do we talk about current ? when discussing current , terms like through and in make a lot of sense . current flows through a resistor ; current flows in a wire . if you hear , `` the current across ... '' , it should sound odd . voltage to get our initial toehold on the concept of voltage , let 's look at an analogy : voltage resembles gravity for a mass $ m $ , a change of height $ h $ corresponds to a change in potential energy , $ \delta u = mg\delta h $ . for a charged particle $ q $ , a voltage $ v $ corresponds to a change in potential energy , $ \delta u = qv $ . voltage in an electric circuit is analogous to the product of $ g\cdot \delta h $ . where $ g $ is the acceleration due to gravity and $ \delta h $ is the change of height . a ball at the top of the hill rolls down . when it is halfway down , it has given up half of its potential energy . an electron at the top of a voltage `` hill '' travels `` downhill '' through wires and elements of a circuit . it gives up its potential energy , doing work along the way . when the electron is halfway down the hill , it has given up , or `` dropped '' , half of its potential energy . for both the ball and the electron , the trip down the hill happens spontaneously . the ball and electron move towards a lower energy state all by themselves . on the trip down , there can be things in the way of the ball , like trees or bears to bounce off . for electrons , we can guide electrons using wires and make them flow through electronic components —circuit design— and do interesting things along the way . we can express the voltage between two points mathematically as the change of energy experienced by a charge : $ v = \dfrac { \delta u } { q } $ that 's an intuitive description of voltage in a nutshell . power power is defined as the rate energy ( $ \text u $ ) is transformed or transferred over time . we measure power in units of joules/second , also known as watts . ( $ 1 \ , \text { watt } = 1\ , \text { joule } /\text { second } $ ) $ \text { power } = \dfrac { \text du } { \text dt } $ an electric circuit is capable of transferring power . current is the rate of flow of charge , and voltage measures the energy transferred per unit of charge . we can insert these definitions into the equation for power : $ \text { power } = \dfrac { \text du } { \text dt } = \dfrac { \text du } { \text dq } \cdot \dfrac { \text dq } { \text dt } = v \ , i $ electrical power is the product of voltage times current . in units of watts . summary these mental models for current and voltage will get us started on all sorts of interesting electric circuits . if you want to reach beyond this intuitive description of voltage you can read this more formal mathematical description of electric potential and voltage .
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this is a very old historical convention . can current be carried by positive charges ? yes .
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( velocity=d/t ) also if we ca n't do that , could we assume that currents with higher values , where more charges pass a single section in each sec , have current moving faster through them ?
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voltage and current are the cornerstone concepts in electricity . we will create our first mental models for these basic electrical quantities . we will also talk about power , which is what happens when voltage and current act together . charge the concept of electricity arises from an observation of nature . we observe a force between objects , that , like gravity , acts at a distance . the source of this force has been given the name charge . a very noticeable thing about electric force is that it is large , far greater than the force of gravity . unlike gravity , however , there are two types of electric charge . opposite types of charge attract , and like types of charge repel . gravity has only one type : it only attracts , never repels . conductors and insulators conductors are made of atoms whose outer , or valence , electrons have relatively weak bonds to their nuclei , as shown in this fanciful image of a copper atom . when a bunch of metal atoms are together , they gladly share their outer electrons with each other , creating a `` swarm '' of electrons not associated with a particular nucleus . a very small electric force can make the electron swarm move . copper , gold , silver , and aluminum are good conductors . so is saltwater . there are also poor conductors . tungsten—a metal used for light bulb filaments—and carbon—used in graphite form in pencils—are relatively poor conductors because their electrons are less prone to move . insulators are materials whose outer electrons are tightly bound to their nuclei . modest electric forces are not able to pull these electrons free . when an electric force is applied , the electron clouds around the atom stretch and deform in response to the force , but the electrons do not depart . glass , plastic , stone , and air are insulators . even for insulators , though , electric force can always be turned up high enough to rip electrons away—this is called breakdown . that 's what is happening to air molecules when you see a spark . semiconductor materials fall between insulators and conductors . they usually act like insulators , but we can make them act like conductors under certain circumstances . the most well-known semiconductor material is silicon ( atomic number $ 14 $ ) . our ability to finely control the insulating and conducting properties of silicon allows us to create modern marvels like computers and mobile phones . the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current . current is reported as the number of charges per unit time passing through a boundary . visualize placing a boundary all the way through a wire . station yourself near the boundary and count the number of charges passing by . report how much charge passed through the boundary in one second . we assign a positive sign to current corresponding to the direction a positive charge would be moving . since current is the amount of charge passing through a boundary in a fixed amount of time , it can be expressed mathematically using the following equation : $ i = \dfrac { dq } { dt } $ that 's current in a nutshell . a few remarks on current what carries current in metal ? since electrons are free to move about in metals , moving electrons are what makes up the current in metals . the positive nuclei in metal atoms are fixed in place and do not contribute to current . even though electrons have a negative charge and do almost all the work in most electric circuits , we still define a positive current as the direction a positive charge would move . this is a very old historical convention . can current be carried by positive charges ? yes . there are lots of examples . current is carried by both positive and negative charges in saltwater : if we put ordinary table salt in water , it becomes a good conductor . table salt is sodium chloride , nacl . the salt dissolves in water , into free-floating na $ ^+ $ and cl $ ^- $ ions . both ions respond to electric force and move through the saltwater solution , in opposite directions . in this case , the current is composed of moving atoms , both positive and negative ions , not just loose electrons . inside our bodies , electrical currents are moving ions , both positive and negative . the same definition of current works : count the number of charges passing by in a fixed amount of time . what causes current ? charged objects move in response to electric and magnetic forces . these forces come from electric and magnetic fields , which in turn come from the position and motion of other charges . what is the speed of current ? we do n't talk very often about the speed of current . answering the question , `` how fast is the current flowing ? '' requires understanding of a complex physical phenomenon and is not often relevant . current usually is n't about meters per second , it 's about charge per second . more often , we answer the question `` how much current is flowing ? '' all the time . how do we talk about current ? when discussing current , terms like through and in make a lot of sense . current flows through a resistor ; current flows in a wire . if you hear , `` the current across ... '' , it should sound odd . voltage to get our initial toehold on the concept of voltage , let 's look at an analogy : voltage resembles gravity for a mass $ m $ , a change of height $ h $ corresponds to a change in potential energy , $ \delta u = mg\delta h $ . for a charged particle $ q $ , a voltage $ v $ corresponds to a change in potential energy , $ \delta u = qv $ . voltage in an electric circuit is analogous to the product of $ g\cdot \delta h $ . where $ g $ is the acceleration due to gravity and $ \delta h $ is the change of height . a ball at the top of the hill rolls down . when it is halfway down , it has given up half of its potential energy . an electron at the top of a voltage `` hill '' travels `` downhill '' through wires and elements of a circuit . it gives up its potential energy , doing work along the way . when the electron is halfway down the hill , it has given up , or `` dropped '' , half of its potential energy . for both the ball and the electron , the trip down the hill happens spontaneously . the ball and electron move towards a lower energy state all by themselves . on the trip down , there can be things in the way of the ball , like trees or bears to bounce off . for electrons , we can guide electrons using wires and make them flow through electronic components —circuit design— and do interesting things along the way . we can express the voltage between two points mathematically as the change of energy experienced by a charge : $ v = \dfrac { \delta u } { q } $ that 's an intuitive description of voltage in a nutshell . power power is defined as the rate energy ( $ \text u $ ) is transformed or transferred over time . we measure power in units of joules/second , also known as watts . ( $ 1 \ , \text { watt } = 1\ , \text { joule } /\text { second } $ ) $ \text { power } = \dfrac { \text du } { \text dt } $ an electric circuit is capable of transferring power . current is the rate of flow of charge , and voltage measures the energy transferred per unit of charge . we can insert these definitions into the equation for power : $ \text { power } = \dfrac { \text du } { \text dt } = \dfrac { \text du } { \text dq } \cdot \dfrac { \text dq } { \text dt } = v \ , i $ electrical power is the product of voltage times current . in units of watts . summary these mental models for current and voltage will get us started on all sorts of interesting electric circuits . if you want to reach beyond this intuitive description of voltage you can read this more formal mathematical description of electric potential and voltage .
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table salt is sodium chloride , nacl . the salt dissolves in water , into free-floating na $ ^+ $ and cl $ ^- $ ions . both ions respond to electric force and move through the saltwater solution , in opposite directions .
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if we are talking about saltwater ( with dissolved na+ ions , cl- ions ) , do the ions flow through the wire to the terminals of the battery ?
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voltage and current are the cornerstone concepts in electricity . we will create our first mental models for these basic electrical quantities . we will also talk about power , which is what happens when voltage and current act together . charge the concept of electricity arises from an observation of nature . we observe a force between objects , that , like gravity , acts at a distance . the source of this force has been given the name charge . a very noticeable thing about electric force is that it is large , far greater than the force of gravity . unlike gravity , however , there are two types of electric charge . opposite types of charge attract , and like types of charge repel . gravity has only one type : it only attracts , never repels . conductors and insulators conductors are made of atoms whose outer , or valence , electrons have relatively weak bonds to their nuclei , as shown in this fanciful image of a copper atom . when a bunch of metal atoms are together , they gladly share their outer electrons with each other , creating a `` swarm '' of electrons not associated with a particular nucleus . a very small electric force can make the electron swarm move . copper , gold , silver , and aluminum are good conductors . so is saltwater . there are also poor conductors . tungsten—a metal used for light bulb filaments—and carbon—used in graphite form in pencils—are relatively poor conductors because their electrons are less prone to move . insulators are materials whose outer electrons are tightly bound to their nuclei . modest electric forces are not able to pull these electrons free . when an electric force is applied , the electron clouds around the atom stretch and deform in response to the force , but the electrons do not depart . glass , plastic , stone , and air are insulators . even for insulators , though , electric force can always be turned up high enough to rip electrons away—this is called breakdown . that 's what is happening to air molecules when you see a spark . semiconductor materials fall between insulators and conductors . they usually act like insulators , but we can make them act like conductors under certain circumstances . the most well-known semiconductor material is silicon ( atomic number $ 14 $ ) . our ability to finely control the insulating and conducting properties of silicon allows us to create modern marvels like computers and mobile phones . the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current . current is reported as the number of charges per unit time passing through a boundary . visualize placing a boundary all the way through a wire . station yourself near the boundary and count the number of charges passing by . report how much charge passed through the boundary in one second . we assign a positive sign to current corresponding to the direction a positive charge would be moving . since current is the amount of charge passing through a boundary in a fixed amount of time , it can be expressed mathematically using the following equation : $ i = \dfrac { dq } { dt } $ that 's current in a nutshell . a few remarks on current what carries current in metal ? since electrons are free to move about in metals , moving electrons are what makes up the current in metals . the positive nuclei in metal atoms are fixed in place and do not contribute to current . even though electrons have a negative charge and do almost all the work in most electric circuits , we still define a positive current as the direction a positive charge would move . this is a very old historical convention . can current be carried by positive charges ? yes . there are lots of examples . current is carried by both positive and negative charges in saltwater : if we put ordinary table salt in water , it becomes a good conductor . table salt is sodium chloride , nacl . the salt dissolves in water , into free-floating na $ ^+ $ and cl $ ^- $ ions . both ions respond to electric force and move through the saltwater solution , in opposite directions . in this case , the current is composed of moving atoms , both positive and negative ions , not just loose electrons . inside our bodies , electrical currents are moving ions , both positive and negative . the same definition of current works : count the number of charges passing by in a fixed amount of time . what causes current ? charged objects move in response to electric and magnetic forces . these forces come from electric and magnetic fields , which in turn come from the position and motion of other charges . what is the speed of current ? we do n't talk very often about the speed of current . answering the question , `` how fast is the current flowing ? '' requires understanding of a complex physical phenomenon and is not often relevant . current usually is n't about meters per second , it 's about charge per second . more often , we answer the question `` how much current is flowing ? '' all the time . how do we talk about current ? when discussing current , terms like through and in make a lot of sense . current flows through a resistor ; current flows in a wire . if you hear , `` the current across ... '' , it should sound odd . voltage to get our initial toehold on the concept of voltage , let 's look at an analogy : voltage resembles gravity for a mass $ m $ , a change of height $ h $ corresponds to a change in potential energy , $ \delta u = mg\delta h $ . for a charged particle $ q $ , a voltage $ v $ corresponds to a change in potential energy , $ \delta u = qv $ . voltage in an electric circuit is analogous to the product of $ g\cdot \delta h $ . where $ g $ is the acceleration due to gravity and $ \delta h $ is the change of height . a ball at the top of the hill rolls down . when it is halfway down , it has given up half of its potential energy . an electron at the top of a voltage `` hill '' travels `` downhill '' through wires and elements of a circuit . it gives up its potential energy , doing work along the way . when the electron is halfway down the hill , it has given up , or `` dropped '' , half of its potential energy . for both the ball and the electron , the trip down the hill happens spontaneously . the ball and electron move towards a lower energy state all by themselves . on the trip down , there can be things in the way of the ball , like trees or bears to bounce off . for electrons , we can guide electrons using wires and make them flow through electronic components —circuit design— and do interesting things along the way . we can express the voltage between two points mathematically as the change of energy experienced by a charge : $ v = \dfrac { \delta u } { q } $ that 's an intuitive description of voltage in a nutshell . power power is defined as the rate energy ( $ \text u $ ) is transformed or transferred over time . we measure power in units of joules/second , also known as watts . ( $ 1 \ , \text { watt } = 1\ , \text { joule } /\text { second } $ ) $ \text { power } = \dfrac { \text du } { \text dt } $ an electric circuit is capable of transferring power . current is the rate of flow of charge , and voltage measures the energy transferred per unit of charge . we can insert these definitions into the equation for power : $ \text { power } = \dfrac { \text du } { \text dt } = \dfrac { \text du } { \text dq } \cdot \dfrac { \text dq } { \text dt } = v \ , i $ electrical power is the product of voltage times current . in units of watts . summary these mental models for current and voltage will get us started on all sorts of interesting electric circuits . if you want to reach beyond this intuitive description of voltage you can read this more formal mathematical description of electric potential and voltage .
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the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current .
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is there anything wrong with exchanging `` charge flows in a current '' into `` electrons flow in a current '' ?
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voltage and current are the cornerstone concepts in electricity . we will create our first mental models for these basic electrical quantities . we will also talk about power , which is what happens when voltage and current act together . charge the concept of electricity arises from an observation of nature . we observe a force between objects , that , like gravity , acts at a distance . the source of this force has been given the name charge . a very noticeable thing about electric force is that it is large , far greater than the force of gravity . unlike gravity , however , there are two types of electric charge . opposite types of charge attract , and like types of charge repel . gravity has only one type : it only attracts , never repels . conductors and insulators conductors are made of atoms whose outer , or valence , electrons have relatively weak bonds to their nuclei , as shown in this fanciful image of a copper atom . when a bunch of metal atoms are together , they gladly share their outer electrons with each other , creating a `` swarm '' of electrons not associated with a particular nucleus . a very small electric force can make the electron swarm move . copper , gold , silver , and aluminum are good conductors . so is saltwater . there are also poor conductors . tungsten—a metal used for light bulb filaments—and carbon—used in graphite form in pencils—are relatively poor conductors because their electrons are less prone to move . insulators are materials whose outer electrons are tightly bound to their nuclei . modest electric forces are not able to pull these electrons free . when an electric force is applied , the electron clouds around the atom stretch and deform in response to the force , but the electrons do not depart . glass , plastic , stone , and air are insulators . even for insulators , though , electric force can always be turned up high enough to rip electrons away—this is called breakdown . that 's what is happening to air molecules when you see a spark . semiconductor materials fall between insulators and conductors . they usually act like insulators , but we can make them act like conductors under certain circumstances . the most well-known semiconductor material is silicon ( atomic number $ 14 $ ) . our ability to finely control the insulating and conducting properties of silicon allows us to create modern marvels like computers and mobile phones . the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current . current is reported as the number of charges per unit time passing through a boundary . visualize placing a boundary all the way through a wire . station yourself near the boundary and count the number of charges passing by . report how much charge passed through the boundary in one second . we assign a positive sign to current corresponding to the direction a positive charge would be moving . since current is the amount of charge passing through a boundary in a fixed amount of time , it can be expressed mathematically using the following equation : $ i = \dfrac { dq } { dt } $ that 's current in a nutshell . a few remarks on current what carries current in metal ? since electrons are free to move about in metals , moving electrons are what makes up the current in metals . the positive nuclei in metal atoms are fixed in place and do not contribute to current . even though electrons have a negative charge and do almost all the work in most electric circuits , we still define a positive current as the direction a positive charge would move . this is a very old historical convention . can current be carried by positive charges ? yes . there are lots of examples . current is carried by both positive and negative charges in saltwater : if we put ordinary table salt in water , it becomes a good conductor . table salt is sodium chloride , nacl . the salt dissolves in water , into free-floating na $ ^+ $ and cl $ ^- $ ions . both ions respond to electric force and move through the saltwater solution , in opposite directions . in this case , the current is composed of moving atoms , both positive and negative ions , not just loose electrons . inside our bodies , electrical currents are moving ions , both positive and negative . the same definition of current works : count the number of charges passing by in a fixed amount of time . what causes current ? charged objects move in response to electric and magnetic forces . these forces come from electric and magnetic fields , which in turn come from the position and motion of other charges . what is the speed of current ? we do n't talk very often about the speed of current . answering the question , `` how fast is the current flowing ? '' requires understanding of a complex physical phenomenon and is not often relevant . current usually is n't about meters per second , it 's about charge per second . more often , we answer the question `` how much current is flowing ? '' all the time . how do we talk about current ? when discussing current , terms like through and in make a lot of sense . current flows through a resistor ; current flows in a wire . if you hear , `` the current across ... '' , it should sound odd . voltage to get our initial toehold on the concept of voltage , let 's look at an analogy : voltage resembles gravity for a mass $ m $ , a change of height $ h $ corresponds to a change in potential energy , $ \delta u = mg\delta h $ . for a charged particle $ q $ , a voltage $ v $ corresponds to a change in potential energy , $ \delta u = qv $ . voltage in an electric circuit is analogous to the product of $ g\cdot \delta h $ . where $ g $ is the acceleration due to gravity and $ \delta h $ is the change of height . a ball at the top of the hill rolls down . when it is halfway down , it has given up half of its potential energy . an electron at the top of a voltage `` hill '' travels `` downhill '' through wires and elements of a circuit . it gives up its potential energy , doing work along the way . when the electron is halfway down the hill , it has given up , or `` dropped '' , half of its potential energy . for both the ball and the electron , the trip down the hill happens spontaneously . the ball and electron move towards a lower energy state all by themselves . on the trip down , there can be things in the way of the ball , like trees or bears to bounce off . for electrons , we can guide electrons using wires and make them flow through electronic components —circuit design— and do interesting things along the way . we can express the voltage between two points mathematically as the change of energy experienced by a charge : $ v = \dfrac { \delta u } { q } $ that 's an intuitive description of voltage in a nutshell . power power is defined as the rate energy ( $ \text u $ ) is transformed or transferred over time . we measure power in units of joules/second , also known as watts . ( $ 1 \ , \text { watt } = 1\ , \text { joule } /\text { second } $ ) $ \text { power } = \dfrac { \text du } { \text dt } $ an electric circuit is capable of transferring power . current is the rate of flow of charge , and voltage measures the energy transferred per unit of charge . we can insert these definitions into the equation for power : $ \text { power } = \dfrac { \text du } { \text dt } = \dfrac { \text du } { \text dq } \cdot \dfrac { \text dq } { \text dt } = v \ , i $ electrical power is the product of voltage times current . in units of watts . summary these mental models for current and voltage will get us started on all sorts of interesting electric circuits . if you want to reach beyond this intuitive description of voltage you can read this more formal mathematical description of electric potential and voltage .
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the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current .
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i know that current is a flow of electrons , but what makes them actually flow from atom to atom ?
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voltage and current are the cornerstone concepts in electricity . we will create our first mental models for these basic electrical quantities . we will also talk about power , which is what happens when voltage and current act together . charge the concept of electricity arises from an observation of nature . we observe a force between objects , that , like gravity , acts at a distance . the source of this force has been given the name charge . a very noticeable thing about electric force is that it is large , far greater than the force of gravity . unlike gravity , however , there are two types of electric charge . opposite types of charge attract , and like types of charge repel . gravity has only one type : it only attracts , never repels . conductors and insulators conductors are made of atoms whose outer , or valence , electrons have relatively weak bonds to their nuclei , as shown in this fanciful image of a copper atom . when a bunch of metal atoms are together , they gladly share their outer electrons with each other , creating a `` swarm '' of electrons not associated with a particular nucleus . a very small electric force can make the electron swarm move . copper , gold , silver , and aluminum are good conductors . so is saltwater . there are also poor conductors . tungsten—a metal used for light bulb filaments—and carbon—used in graphite form in pencils—are relatively poor conductors because their electrons are less prone to move . insulators are materials whose outer electrons are tightly bound to their nuclei . modest electric forces are not able to pull these electrons free . when an electric force is applied , the electron clouds around the atom stretch and deform in response to the force , but the electrons do not depart . glass , plastic , stone , and air are insulators . even for insulators , though , electric force can always be turned up high enough to rip electrons away—this is called breakdown . that 's what is happening to air molecules when you see a spark . semiconductor materials fall between insulators and conductors . they usually act like insulators , but we can make them act like conductors under certain circumstances . the most well-known semiconductor material is silicon ( atomic number $ 14 $ ) . our ability to finely control the insulating and conducting properties of silicon allows us to create modern marvels like computers and mobile phones . the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current . current is reported as the number of charges per unit time passing through a boundary . visualize placing a boundary all the way through a wire . station yourself near the boundary and count the number of charges passing by . report how much charge passed through the boundary in one second . we assign a positive sign to current corresponding to the direction a positive charge would be moving . since current is the amount of charge passing through a boundary in a fixed amount of time , it can be expressed mathematically using the following equation : $ i = \dfrac { dq } { dt } $ that 's current in a nutshell . a few remarks on current what carries current in metal ? since electrons are free to move about in metals , moving electrons are what makes up the current in metals . the positive nuclei in metal atoms are fixed in place and do not contribute to current . even though electrons have a negative charge and do almost all the work in most electric circuits , we still define a positive current as the direction a positive charge would move . this is a very old historical convention . can current be carried by positive charges ? yes . there are lots of examples . current is carried by both positive and negative charges in saltwater : if we put ordinary table salt in water , it becomes a good conductor . table salt is sodium chloride , nacl . the salt dissolves in water , into free-floating na $ ^+ $ and cl $ ^- $ ions . both ions respond to electric force and move through the saltwater solution , in opposite directions . in this case , the current is composed of moving atoms , both positive and negative ions , not just loose electrons . inside our bodies , electrical currents are moving ions , both positive and negative . the same definition of current works : count the number of charges passing by in a fixed amount of time . what causes current ? charged objects move in response to electric and magnetic forces . these forces come from electric and magnetic fields , which in turn come from the position and motion of other charges . what is the speed of current ? we do n't talk very often about the speed of current . answering the question , `` how fast is the current flowing ? '' requires understanding of a complex physical phenomenon and is not often relevant . current usually is n't about meters per second , it 's about charge per second . more often , we answer the question `` how much current is flowing ? '' all the time . how do we talk about current ? when discussing current , terms like through and in make a lot of sense . current flows through a resistor ; current flows in a wire . if you hear , `` the current across ... '' , it should sound odd . voltage to get our initial toehold on the concept of voltage , let 's look at an analogy : voltage resembles gravity for a mass $ m $ , a change of height $ h $ corresponds to a change in potential energy , $ \delta u = mg\delta h $ . for a charged particle $ q $ , a voltage $ v $ corresponds to a change in potential energy , $ \delta u = qv $ . voltage in an electric circuit is analogous to the product of $ g\cdot \delta h $ . where $ g $ is the acceleration due to gravity and $ \delta h $ is the change of height . a ball at the top of the hill rolls down . when it is halfway down , it has given up half of its potential energy . an electron at the top of a voltage `` hill '' travels `` downhill '' through wires and elements of a circuit . it gives up its potential energy , doing work along the way . when the electron is halfway down the hill , it has given up , or `` dropped '' , half of its potential energy . for both the ball and the electron , the trip down the hill happens spontaneously . the ball and electron move towards a lower energy state all by themselves . on the trip down , there can be things in the way of the ball , like trees or bears to bounce off . for electrons , we can guide electrons using wires and make them flow through electronic components —circuit design— and do interesting things along the way . we can express the voltage between two points mathematically as the change of energy experienced by a charge : $ v = \dfrac { \delta u } { q } $ that 's an intuitive description of voltage in a nutshell . power power is defined as the rate energy ( $ \text u $ ) is transformed or transferred over time . we measure power in units of joules/second , also known as watts . ( $ 1 \ , \text { watt } = 1\ , \text { joule } /\text { second } $ ) $ \text { power } = \dfrac { \text du } { \text dt } $ an electric circuit is capable of transferring power . current is the rate of flow of charge , and voltage measures the energy transferred per unit of charge . we can insert these definitions into the equation for power : $ \text { power } = \dfrac { \text du } { \text dt } = \dfrac { \text du } { \text dq } \cdot \dfrac { \text dq } { \text dt } = v \ , i $ electrical power is the product of voltage times current . in units of watts . summary these mental models for current and voltage will get us started on all sorts of interesting electric circuits . if you want to reach beyond this intuitive description of voltage you can read this more formal mathematical description of electric potential and voltage .
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the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current .
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in the formulas of current and power , what does the `` d '' represent ?
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voltage and current are the cornerstone concepts in electricity . we will create our first mental models for these basic electrical quantities . we will also talk about power , which is what happens when voltage and current act together . charge the concept of electricity arises from an observation of nature . we observe a force between objects , that , like gravity , acts at a distance . the source of this force has been given the name charge . a very noticeable thing about electric force is that it is large , far greater than the force of gravity . unlike gravity , however , there are two types of electric charge . opposite types of charge attract , and like types of charge repel . gravity has only one type : it only attracts , never repels . conductors and insulators conductors are made of atoms whose outer , or valence , electrons have relatively weak bonds to their nuclei , as shown in this fanciful image of a copper atom . when a bunch of metal atoms are together , they gladly share their outer electrons with each other , creating a `` swarm '' of electrons not associated with a particular nucleus . a very small electric force can make the electron swarm move . copper , gold , silver , and aluminum are good conductors . so is saltwater . there are also poor conductors . tungsten—a metal used for light bulb filaments—and carbon—used in graphite form in pencils—are relatively poor conductors because their electrons are less prone to move . insulators are materials whose outer electrons are tightly bound to their nuclei . modest electric forces are not able to pull these electrons free . when an electric force is applied , the electron clouds around the atom stretch and deform in response to the force , but the electrons do not depart . glass , plastic , stone , and air are insulators . even for insulators , though , electric force can always be turned up high enough to rip electrons away—this is called breakdown . that 's what is happening to air molecules when you see a spark . semiconductor materials fall between insulators and conductors . they usually act like insulators , but we can make them act like conductors under certain circumstances . the most well-known semiconductor material is silicon ( atomic number $ 14 $ ) . our ability to finely control the insulating and conducting properties of silicon allows us to create modern marvels like computers and mobile phones . the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current . current is reported as the number of charges per unit time passing through a boundary . visualize placing a boundary all the way through a wire . station yourself near the boundary and count the number of charges passing by . report how much charge passed through the boundary in one second . we assign a positive sign to current corresponding to the direction a positive charge would be moving . since current is the amount of charge passing through a boundary in a fixed amount of time , it can be expressed mathematically using the following equation : $ i = \dfrac { dq } { dt } $ that 's current in a nutshell . a few remarks on current what carries current in metal ? since electrons are free to move about in metals , moving electrons are what makes up the current in metals . the positive nuclei in metal atoms are fixed in place and do not contribute to current . even though electrons have a negative charge and do almost all the work in most electric circuits , we still define a positive current as the direction a positive charge would move . this is a very old historical convention . can current be carried by positive charges ? yes . there are lots of examples . current is carried by both positive and negative charges in saltwater : if we put ordinary table salt in water , it becomes a good conductor . table salt is sodium chloride , nacl . the salt dissolves in water , into free-floating na $ ^+ $ and cl $ ^- $ ions . both ions respond to electric force and move through the saltwater solution , in opposite directions . in this case , the current is composed of moving atoms , both positive and negative ions , not just loose electrons . inside our bodies , electrical currents are moving ions , both positive and negative . the same definition of current works : count the number of charges passing by in a fixed amount of time . what causes current ? charged objects move in response to electric and magnetic forces . these forces come from electric and magnetic fields , which in turn come from the position and motion of other charges . what is the speed of current ? we do n't talk very often about the speed of current . answering the question , `` how fast is the current flowing ? '' requires understanding of a complex physical phenomenon and is not often relevant . current usually is n't about meters per second , it 's about charge per second . more often , we answer the question `` how much current is flowing ? '' all the time . how do we talk about current ? when discussing current , terms like through and in make a lot of sense . current flows through a resistor ; current flows in a wire . if you hear , `` the current across ... '' , it should sound odd . voltage to get our initial toehold on the concept of voltage , let 's look at an analogy : voltage resembles gravity for a mass $ m $ , a change of height $ h $ corresponds to a change in potential energy , $ \delta u = mg\delta h $ . for a charged particle $ q $ , a voltage $ v $ corresponds to a change in potential energy , $ \delta u = qv $ . voltage in an electric circuit is analogous to the product of $ g\cdot \delta h $ . where $ g $ is the acceleration due to gravity and $ \delta h $ is the change of height . a ball at the top of the hill rolls down . when it is halfway down , it has given up half of its potential energy . an electron at the top of a voltage `` hill '' travels `` downhill '' through wires and elements of a circuit . it gives up its potential energy , doing work along the way . when the electron is halfway down the hill , it has given up , or `` dropped '' , half of its potential energy . for both the ball and the electron , the trip down the hill happens spontaneously . the ball and electron move towards a lower energy state all by themselves . on the trip down , there can be things in the way of the ball , like trees or bears to bounce off . for electrons , we can guide electrons using wires and make them flow through electronic components —circuit design— and do interesting things along the way . we can express the voltage between two points mathematically as the change of energy experienced by a charge : $ v = \dfrac { \delta u } { q } $ that 's an intuitive description of voltage in a nutshell . power power is defined as the rate energy ( $ \text u $ ) is transformed or transferred over time . we measure power in units of joules/second , also known as watts . ( $ 1 \ , \text { watt } = 1\ , \text { joule } /\text { second } $ ) $ \text { power } = \dfrac { \text du } { \text dt } $ an electric circuit is capable of transferring power . current is the rate of flow of charge , and voltage measures the energy transferred per unit of charge . we can insert these definitions into the equation for power : $ \text { power } = \dfrac { \text du } { \text dt } = \dfrac { \text du } { \text dq } \cdot \dfrac { \text dq } { \text dt } = v \ , i $ electrical power is the product of voltage times current . in units of watts . summary these mental models for current and voltage will get us started on all sorts of interesting electric circuits . if you want to reach beyond this intuitive description of voltage you can read this more formal mathematical description of electric potential and voltage .
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we will create our first mental models for these basic electrical quantities . we will also talk about power , which is what happens when voltage and current act together . charge the concept of electricity arises from an observation of nature .
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if power changes , then how are voltage and current affected by it and by how much ?
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voltage and current are the cornerstone concepts in electricity . we will create our first mental models for these basic electrical quantities . we will also talk about power , which is what happens when voltage and current act together . charge the concept of electricity arises from an observation of nature . we observe a force between objects , that , like gravity , acts at a distance . the source of this force has been given the name charge . a very noticeable thing about electric force is that it is large , far greater than the force of gravity . unlike gravity , however , there are two types of electric charge . opposite types of charge attract , and like types of charge repel . gravity has only one type : it only attracts , never repels . conductors and insulators conductors are made of atoms whose outer , or valence , electrons have relatively weak bonds to their nuclei , as shown in this fanciful image of a copper atom . when a bunch of metal atoms are together , they gladly share their outer electrons with each other , creating a `` swarm '' of electrons not associated with a particular nucleus . a very small electric force can make the electron swarm move . copper , gold , silver , and aluminum are good conductors . so is saltwater . there are also poor conductors . tungsten—a metal used for light bulb filaments—and carbon—used in graphite form in pencils—are relatively poor conductors because their electrons are less prone to move . insulators are materials whose outer electrons are tightly bound to their nuclei . modest electric forces are not able to pull these electrons free . when an electric force is applied , the electron clouds around the atom stretch and deform in response to the force , but the electrons do not depart . glass , plastic , stone , and air are insulators . even for insulators , though , electric force can always be turned up high enough to rip electrons away—this is called breakdown . that 's what is happening to air molecules when you see a spark . semiconductor materials fall between insulators and conductors . they usually act like insulators , but we can make them act like conductors under certain circumstances . the most well-known semiconductor material is silicon ( atomic number $ 14 $ ) . our ability to finely control the insulating and conducting properties of silicon allows us to create modern marvels like computers and mobile phones . the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current . current is reported as the number of charges per unit time passing through a boundary . visualize placing a boundary all the way through a wire . station yourself near the boundary and count the number of charges passing by . report how much charge passed through the boundary in one second . we assign a positive sign to current corresponding to the direction a positive charge would be moving . since current is the amount of charge passing through a boundary in a fixed amount of time , it can be expressed mathematically using the following equation : $ i = \dfrac { dq } { dt } $ that 's current in a nutshell . a few remarks on current what carries current in metal ? since electrons are free to move about in metals , moving electrons are what makes up the current in metals . the positive nuclei in metal atoms are fixed in place and do not contribute to current . even though electrons have a negative charge and do almost all the work in most electric circuits , we still define a positive current as the direction a positive charge would move . this is a very old historical convention . can current be carried by positive charges ? yes . there are lots of examples . current is carried by both positive and negative charges in saltwater : if we put ordinary table salt in water , it becomes a good conductor . table salt is sodium chloride , nacl . the salt dissolves in water , into free-floating na $ ^+ $ and cl $ ^- $ ions . both ions respond to electric force and move through the saltwater solution , in opposite directions . in this case , the current is composed of moving atoms , both positive and negative ions , not just loose electrons . inside our bodies , electrical currents are moving ions , both positive and negative . the same definition of current works : count the number of charges passing by in a fixed amount of time . what causes current ? charged objects move in response to electric and magnetic forces . these forces come from electric and magnetic fields , which in turn come from the position and motion of other charges . what is the speed of current ? we do n't talk very often about the speed of current . answering the question , `` how fast is the current flowing ? '' requires understanding of a complex physical phenomenon and is not often relevant . current usually is n't about meters per second , it 's about charge per second . more often , we answer the question `` how much current is flowing ? '' all the time . how do we talk about current ? when discussing current , terms like through and in make a lot of sense . current flows through a resistor ; current flows in a wire . if you hear , `` the current across ... '' , it should sound odd . voltage to get our initial toehold on the concept of voltage , let 's look at an analogy : voltage resembles gravity for a mass $ m $ , a change of height $ h $ corresponds to a change in potential energy , $ \delta u = mg\delta h $ . for a charged particle $ q $ , a voltage $ v $ corresponds to a change in potential energy , $ \delta u = qv $ . voltage in an electric circuit is analogous to the product of $ g\cdot \delta h $ . where $ g $ is the acceleration due to gravity and $ \delta h $ is the change of height . a ball at the top of the hill rolls down . when it is halfway down , it has given up half of its potential energy . an electron at the top of a voltage `` hill '' travels `` downhill '' through wires and elements of a circuit . it gives up its potential energy , doing work along the way . when the electron is halfway down the hill , it has given up , or `` dropped '' , half of its potential energy . for both the ball and the electron , the trip down the hill happens spontaneously . the ball and electron move towards a lower energy state all by themselves . on the trip down , there can be things in the way of the ball , like trees or bears to bounce off . for electrons , we can guide electrons using wires and make them flow through electronic components —circuit design— and do interesting things along the way . we can express the voltage between two points mathematically as the change of energy experienced by a charge : $ v = \dfrac { \delta u } { q } $ that 's an intuitive description of voltage in a nutshell . power power is defined as the rate energy ( $ \text u $ ) is transformed or transferred over time . we measure power in units of joules/second , also known as watts . ( $ 1 \ , \text { watt } = 1\ , \text { joule } /\text { second } $ ) $ \text { power } = \dfrac { \text du } { \text dt } $ an electric circuit is capable of transferring power . current is the rate of flow of charge , and voltage measures the energy transferred per unit of charge . we can insert these definitions into the equation for power : $ \text { power } = \dfrac { \text du } { \text dt } = \dfrac { \text du } { \text dq } \cdot \dfrac { \text dq } { \text dt } = v \ , i $ electrical power is the product of voltage times current . in units of watts . summary these mental models for current and voltage will get us started on all sorts of interesting electric circuits . if you want to reach beyond this intuitive description of voltage you can read this more formal mathematical description of electric potential and voltage .
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unlike gravity , however , there are two types of electric charge . opposite types of charge attract , and like types of charge repel . gravity has only one type : it only attracts , never repels .
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it does n't repel but fails to attract ( thank god ) creating a weird harmony , does electricity have a similar effect ?
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voltage and current are the cornerstone concepts in electricity . we will create our first mental models for these basic electrical quantities . we will also talk about power , which is what happens when voltage and current act together . charge the concept of electricity arises from an observation of nature . we observe a force between objects , that , like gravity , acts at a distance . the source of this force has been given the name charge . a very noticeable thing about electric force is that it is large , far greater than the force of gravity . unlike gravity , however , there are two types of electric charge . opposite types of charge attract , and like types of charge repel . gravity has only one type : it only attracts , never repels . conductors and insulators conductors are made of atoms whose outer , or valence , electrons have relatively weak bonds to their nuclei , as shown in this fanciful image of a copper atom . when a bunch of metal atoms are together , they gladly share their outer electrons with each other , creating a `` swarm '' of electrons not associated with a particular nucleus . a very small electric force can make the electron swarm move . copper , gold , silver , and aluminum are good conductors . so is saltwater . there are also poor conductors . tungsten—a metal used for light bulb filaments—and carbon—used in graphite form in pencils—are relatively poor conductors because their electrons are less prone to move . insulators are materials whose outer electrons are tightly bound to their nuclei . modest electric forces are not able to pull these electrons free . when an electric force is applied , the electron clouds around the atom stretch and deform in response to the force , but the electrons do not depart . glass , plastic , stone , and air are insulators . even for insulators , though , electric force can always be turned up high enough to rip electrons away—this is called breakdown . that 's what is happening to air molecules when you see a spark . semiconductor materials fall between insulators and conductors . they usually act like insulators , but we can make them act like conductors under certain circumstances . the most well-known semiconductor material is silicon ( atomic number $ 14 $ ) . our ability to finely control the insulating and conducting properties of silicon allows us to create modern marvels like computers and mobile phones . the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current . current is reported as the number of charges per unit time passing through a boundary . visualize placing a boundary all the way through a wire . station yourself near the boundary and count the number of charges passing by . report how much charge passed through the boundary in one second . we assign a positive sign to current corresponding to the direction a positive charge would be moving . since current is the amount of charge passing through a boundary in a fixed amount of time , it can be expressed mathematically using the following equation : $ i = \dfrac { dq } { dt } $ that 's current in a nutshell . a few remarks on current what carries current in metal ? since electrons are free to move about in metals , moving electrons are what makes up the current in metals . the positive nuclei in metal atoms are fixed in place and do not contribute to current . even though electrons have a negative charge and do almost all the work in most electric circuits , we still define a positive current as the direction a positive charge would move . this is a very old historical convention . can current be carried by positive charges ? yes . there are lots of examples . current is carried by both positive and negative charges in saltwater : if we put ordinary table salt in water , it becomes a good conductor . table salt is sodium chloride , nacl . the salt dissolves in water , into free-floating na $ ^+ $ and cl $ ^- $ ions . both ions respond to electric force and move through the saltwater solution , in opposite directions . in this case , the current is composed of moving atoms , both positive and negative ions , not just loose electrons . inside our bodies , electrical currents are moving ions , both positive and negative . the same definition of current works : count the number of charges passing by in a fixed amount of time . what causes current ? charged objects move in response to electric and magnetic forces . these forces come from electric and magnetic fields , which in turn come from the position and motion of other charges . what is the speed of current ? we do n't talk very often about the speed of current . answering the question , `` how fast is the current flowing ? '' requires understanding of a complex physical phenomenon and is not often relevant . current usually is n't about meters per second , it 's about charge per second . more often , we answer the question `` how much current is flowing ? '' all the time . how do we talk about current ? when discussing current , terms like through and in make a lot of sense . current flows through a resistor ; current flows in a wire . if you hear , `` the current across ... '' , it should sound odd . voltage to get our initial toehold on the concept of voltage , let 's look at an analogy : voltage resembles gravity for a mass $ m $ , a change of height $ h $ corresponds to a change in potential energy , $ \delta u = mg\delta h $ . for a charged particle $ q $ , a voltage $ v $ corresponds to a change in potential energy , $ \delta u = qv $ . voltage in an electric circuit is analogous to the product of $ g\cdot \delta h $ . where $ g $ is the acceleration due to gravity and $ \delta h $ is the change of height . a ball at the top of the hill rolls down . when it is halfway down , it has given up half of its potential energy . an electron at the top of a voltage `` hill '' travels `` downhill '' through wires and elements of a circuit . it gives up its potential energy , doing work along the way . when the electron is halfway down the hill , it has given up , or `` dropped '' , half of its potential energy . for both the ball and the electron , the trip down the hill happens spontaneously . the ball and electron move towards a lower energy state all by themselves . on the trip down , there can be things in the way of the ball , like trees or bears to bounce off . for electrons , we can guide electrons using wires and make them flow through electronic components —circuit design— and do interesting things along the way . we can express the voltage between two points mathematically as the change of energy experienced by a charge : $ v = \dfrac { \delta u } { q } $ that 's an intuitive description of voltage in a nutshell . power power is defined as the rate energy ( $ \text u $ ) is transformed or transferred over time . we measure power in units of joules/second , also known as watts . ( $ 1 \ , \text { watt } = 1\ , \text { joule } /\text { second } $ ) $ \text { power } = \dfrac { \text du } { \text dt } $ an electric circuit is capable of transferring power . current is the rate of flow of charge , and voltage measures the energy transferred per unit of charge . we can insert these definitions into the equation for power : $ \text { power } = \dfrac { \text du } { \text dt } = \dfrac { \text du } { \text dq } \cdot \dfrac { \text dq } { \text dt } = v \ , i $ electrical power is the product of voltage times current . in units of watts . summary these mental models for current and voltage will get us started on all sorts of interesting electric circuits . if you want to reach beyond this intuitive description of voltage you can read this more formal mathematical description of electric potential and voltage .
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in units of watts . summary these mental models for current and voltage will get us started on all sorts of interesting electric circuits . if you want to reach beyond this intuitive description of voltage you can read this more formal mathematical description of electric potential and voltage .
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what is the difference between 'voltage ' and 'electric potential ' ?
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voltage and current are the cornerstone concepts in electricity . we will create our first mental models for these basic electrical quantities . we will also talk about power , which is what happens when voltage and current act together . charge the concept of electricity arises from an observation of nature . we observe a force between objects , that , like gravity , acts at a distance . the source of this force has been given the name charge . a very noticeable thing about electric force is that it is large , far greater than the force of gravity . unlike gravity , however , there are two types of electric charge . opposite types of charge attract , and like types of charge repel . gravity has only one type : it only attracts , never repels . conductors and insulators conductors are made of atoms whose outer , or valence , electrons have relatively weak bonds to their nuclei , as shown in this fanciful image of a copper atom . when a bunch of metal atoms are together , they gladly share their outer electrons with each other , creating a `` swarm '' of electrons not associated with a particular nucleus . a very small electric force can make the electron swarm move . copper , gold , silver , and aluminum are good conductors . so is saltwater . there are also poor conductors . tungsten—a metal used for light bulb filaments—and carbon—used in graphite form in pencils—are relatively poor conductors because their electrons are less prone to move . insulators are materials whose outer electrons are tightly bound to their nuclei . modest electric forces are not able to pull these electrons free . when an electric force is applied , the electron clouds around the atom stretch and deform in response to the force , but the electrons do not depart . glass , plastic , stone , and air are insulators . even for insulators , though , electric force can always be turned up high enough to rip electrons away—this is called breakdown . that 's what is happening to air molecules when you see a spark . semiconductor materials fall between insulators and conductors . they usually act like insulators , but we can make them act like conductors under certain circumstances . the most well-known semiconductor material is silicon ( atomic number $ 14 $ ) . our ability to finely control the insulating and conducting properties of silicon allows us to create modern marvels like computers and mobile phones . the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current . current is reported as the number of charges per unit time passing through a boundary . visualize placing a boundary all the way through a wire . station yourself near the boundary and count the number of charges passing by . report how much charge passed through the boundary in one second . we assign a positive sign to current corresponding to the direction a positive charge would be moving . since current is the amount of charge passing through a boundary in a fixed amount of time , it can be expressed mathematically using the following equation : $ i = \dfrac { dq } { dt } $ that 's current in a nutshell . a few remarks on current what carries current in metal ? since electrons are free to move about in metals , moving electrons are what makes up the current in metals . the positive nuclei in metal atoms are fixed in place and do not contribute to current . even though electrons have a negative charge and do almost all the work in most electric circuits , we still define a positive current as the direction a positive charge would move . this is a very old historical convention . can current be carried by positive charges ? yes . there are lots of examples . current is carried by both positive and negative charges in saltwater : if we put ordinary table salt in water , it becomes a good conductor . table salt is sodium chloride , nacl . the salt dissolves in water , into free-floating na $ ^+ $ and cl $ ^- $ ions . both ions respond to electric force and move through the saltwater solution , in opposite directions . in this case , the current is composed of moving atoms , both positive and negative ions , not just loose electrons . inside our bodies , electrical currents are moving ions , both positive and negative . the same definition of current works : count the number of charges passing by in a fixed amount of time . what causes current ? charged objects move in response to electric and magnetic forces . these forces come from electric and magnetic fields , which in turn come from the position and motion of other charges . what is the speed of current ? we do n't talk very often about the speed of current . answering the question , `` how fast is the current flowing ? '' requires understanding of a complex physical phenomenon and is not often relevant . current usually is n't about meters per second , it 's about charge per second . more often , we answer the question `` how much current is flowing ? '' all the time . how do we talk about current ? when discussing current , terms like through and in make a lot of sense . current flows through a resistor ; current flows in a wire . if you hear , `` the current across ... '' , it should sound odd . voltage to get our initial toehold on the concept of voltage , let 's look at an analogy : voltage resembles gravity for a mass $ m $ , a change of height $ h $ corresponds to a change in potential energy , $ \delta u = mg\delta h $ . for a charged particle $ q $ , a voltage $ v $ corresponds to a change in potential energy , $ \delta u = qv $ . voltage in an electric circuit is analogous to the product of $ g\cdot \delta h $ . where $ g $ is the acceleration due to gravity and $ \delta h $ is the change of height . a ball at the top of the hill rolls down . when it is halfway down , it has given up half of its potential energy . an electron at the top of a voltage `` hill '' travels `` downhill '' through wires and elements of a circuit . it gives up its potential energy , doing work along the way . when the electron is halfway down the hill , it has given up , or `` dropped '' , half of its potential energy . for both the ball and the electron , the trip down the hill happens spontaneously . the ball and electron move towards a lower energy state all by themselves . on the trip down , there can be things in the way of the ball , like trees or bears to bounce off . for electrons , we can guide electrons using wires and make them flow through electronic components —circuit design— and do interesting things along the way . we can express the voltage between two points mathematically as the change of energy experienced by a charge : $ v = \dfrac { \delta u } { q } $ that 's an intuitive description of voltage in a nutshell . power power is defined as the rate energy ( $ \text u $ ) is transformed or transferred over time . we measure power in units of joules/second , also known as watts . ( $ 1 \ , \text { watt } = 1\ , \text { joule } /\text { second } $ ) $ \text { power } = \dfrac { \text du } { \text dt } $ an electric circuit is capable of transferring power . current is the rate of flow of charge , and voltage measures the energy transferred per unit of charge . we can insert these definitions into the equation for power : $ \text { power } = \dfrac { \text du } { \text dt } = \dfrac { \text du } { \text dq } \cdot \dfrac { \text dq } { \text dt } = v \ , i $ electrical power is the product of voltage times current . in units of watts . summary these mental models for current and voltage will get us started on all sorts of interesting electric circuits . if you want to reach beyond this intuitive description of voltage you can read this more formal mathematical description of electric potential and voltage .
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an electron at the top of a voltage `` hill '' travels `` downhill '' through wires and elements of a circuit . it gives up its potential energy , doing work along the way . when the electron is halfway down the hill , it has given up , or `` dropped '' , half of its potential energy .
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as well as , what is the difference between 'potential difference ' and 'electric potential ' ?
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voltage and current are the cornerstone concepts in electricity . we will create our first mental models for these basic electrical quantities . we will also talk about power , which is what happens when voltage and current act together . charge the concept of electricity arises from an observation of nature . we observe a force between objects , that , like gravity , acts at a distance . the source of this force has been given the name charge . a very noticeable thing about electric force is that it is large , far greater than the force of gravity . unlike gravity , however , there are two types of electric charge . opposite types of charge attract , and like types of charge repel . gravity has only one type : it only attracts , never repels . conductors and insulators conductors are made of atoms whose outer , or valence , electrons have relatively weak bonds to their nuclei , as shown in this fanciful image of a copper atom . when a bunch of metal atoms are together , they gladly share their outer electrons with each other , creating a `` swarm '' of electrons not associated with a particular nucleus . a very small electric force can make the electron swarm move . copper , gold , silver , and aluminum are good conductors . so is saltwater . there are also poor conductors . tungsten—a metal used for light bulb filaments—and carbon—used in graphite form in pencils—are relatively poor conductors because their electrons are less prone to move . insulators are materials whose outer electrons are tightly bound to their nuclei . modest electric forces are not able to pull these electrons free . when an electric force is applied , the electron clouds around the atom stretch and deform in response to the force , but the electrons do not depart . glass , plastic , stone , and air are insulators . even for insulators , though , electric force can always be turned up high enough to rip electrons away—this is called breakdown . that 's what is happening to air molecules when you see a spark . semiconductor materials fall between insulators and conductors . they usually act like insulators , but we can make them act like conductors under certain circumstances . the most well-known semiconductor material is silicon ( atomic number $ 14 $ ) . our ability to finely control the insulating and conducting properties of silicon allows us to create modern marvels like computers and mobile phones . the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current . current is reported as the number of charges per unit time passing through a boundary . visualize placing a boundary all the way through a wire . station yourself near the boundary and count the number of charges passing by . report how much charge passed through the boundary in one second . we assign a positive sign to current corresponding to the direction a positive charge would be moving . since current is the amount of charge passing through a boundary in a fixed amount of time , it can be expressed mathematically using the following equation : $ i = \dfrac { dq } { dt } $ that 's current in a nutshell . a few remarks on current what carries current in metal ? since electrons are free to move about in metals , moving electrons are what makes up the current in metals . the positive nuclei in metal atoms are fixed in place and do not contribute to current . even though electrons have a negative charge and do almost all the work in most electric circuits , we still define a positive current as the direction a positive charge would move . this is a very old historical convention . can current be carried by positive charges ? yes . there are lots of examples . current is carried by both positive and negative charges in saltwater : if we put ordinary table salt in water , it becomes a good conductor . table salt is sodium chloride , nacl . the salt dissolves in water , into free-floating na $ ^+ $ and cl $ ^- $ ions . both ions respond to electric force and move through the saltwater solution , in opposite directions . in this case , the current is composed of moving atoms , both positive and negative ions , not just loose electrons . inside our bodies , electrical currents are moving ions , both positive and negative . the same definition of current works : count the number of charges passing by in a fixed amount of time . what causes current ? charged objects move in response to electric and magnetic forces . these forces come from electric and magnetic fields , which in turn come from the position and motion of other charges . what is the speed of current ? we do n't talk very often about the speed of current . answering the question , `` how fast is the current flowing ? '' requires understanding of a complex physical phenomenon and is not often relevant . current usually is n't about meters per second , it 's about charge per second . more often , we answer the question `` how much current is flowing ? '' all the time . how do we talk about current ? when discussing current , terms like through and in make a lot of sense . current flows through a resistor ; current flows in a wire . if you hear , `` the current across ... '' , it should sound odd . voltage to get our initial toehold on the concept of voltage , let 's look at an analogy : voltage resembles gravity for a mass $ m $ , a change of height $ h $ corresponds to a change in potential energy , $ \delta u = mg\delta h $ . for a charged particle $ q $ , a voltage $ v $ corresponds to a change in potential energy , $ \delta u = qv $ . voltage in an electric circuit is analogous to the product of $ g\cdot \delta h $ . where $ g $ is the acceleration due to gravity and $ \delta h $ is the change of height . a ball at the top of the hill rolls down . when it is halfway down , it has given up half of its potential energy . an electron at the top of a voltage `` hill '' travels `` downhill '' through wires and elements of a circuit . it gives up its potential energy , doing work along the way . when the electron is halfway down the hill , it has given up , or `` dropped '' , half of its potential energy . for both the ball and the electron , the trip down the hill happens spontaneously . the ball and electron move towards a lower energy state all by themselves . on the trip down , there can be things in the way of the ball , like trees or bears to bounce off . for electrons , we can guide electrons using wires and make them flow through electronic components —circuit design— and do interesting things along the way . we can express the voltage between two points mathematically as the change of energy experienced by a charge : $ v = \dfrac { \delta u } { q } $ that 's an intuitive description of voltage in a nutshell . power power is defined as the rate energy ( $ \text u $ ) is transformed or transferred over time . we measure power in units of joules/second , also known as watts . ( $ 1 \ , \text { watt } = 1\ , \text { joule } /\text { second } $ ) $ \text { power } = \dfrac { \text du } { \text dt } $ an electric circuit is capable of transferring power . current is the rate of flow of charge , and voltage measures the energy transferred per unit of charge . we can insert these definitions into the equation for power : $ \text { power } = \dfrac { \text du } { \text dt } = \dfrac { \text du } { \text dq } \cdot \dfrac { \text dq } { \text dt } = v \ , i $ electrical power is the product of voltage times current . in units of watts . summary these mental models for current and voltage will get us started on all sorts of interesting electric circuits . if you want to reach beyond this intuitive description of voltage you can read this more formal mathematical description of electric potential and voltage .
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the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current .
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what is exact definition of current is it flow of electron ?
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voltage and current are the cornerstone concepts in electricity . we will create our first mental models for these basic electrical quantities . we will also talk about power , which is what happens when voltage and current act together . charge the concept of electricity arises from an observation of nature . we observe a force between objects , that , like gravity , acts at a distance . the source of this force has been given the name charge . a very noticeable thing about electric force is that it is large , far greater than the force of gravity . unlike gravity , however , there are two types of electric charge . opposite types of charge attract , and like types of charge repel . gravity has only one type : it only attracts , never repels . conductors and insulators conductors are made of atoms whose outer , or valence , electrons have relatively weak bonds to their nuclei , as shown in this fanciful image of a copper atom . when a bunch of metal atoms are together , they gladly share their outer electrons with each other , creating a `` swarm '' of electrons not associated with a particular nucleus . a very small electric force can make the electron swarm move . copper , gold , silver , and aluminum are good conductors . so is saltwater . there are also poor conductors . tungsten—a metal used for light bulb filaments—and carbon—used in graphite form in pencils—are relatively poor conductors because their electrons are less prone to move . insulators are materials whose outer electrons are tightly bound to their nuclei . modest electric forces are not able to pull these electrons free . when an electric force is applied , the electron clouds around the atom stretch and deform in response to the force , but the electrons do not depart . glass , plastic , stone , and air are insulators . even for insulators , though , electric force can always be turned up high enough to rip electrons away—this is called breakdown . that 's what is happening to air molecules when you see a spark . semiconductor materials fall between insulators and conductors . they usually act like insulators , but we can make them act like conductors under certain circumstances . the most well-known semiconductor material is silicon ( atomic number $ 14 $ ) . our ability to finely control the insulating and conducting properties of silicon allows us to create modern marvels like computers and mobile phones . the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current . current is reported as the number of charges per unit time passing through a boundary . visualize placing a boundary all the way through a wire . station yourself near the boundary and count the number of charges passing by . report how much charge passed through the boundary in one second . we assign a positive sign to current corresponding to the direction a positive charge would be moving . since current is the amount of charge passing through a boundary in a fixed amount of time , it can be expressed mathematically using the following equation : $ i = \dfrac { dq } { dt } $ that 's current in a nutshell . a few remarks on current what carries current in metal ? since electrons are free to move about in metals , moving electrons are what makes up the current in metals . the positive nuclei in metal atoms are fixed in place and do not contribute to current . even though electrons have a negative charge and do almost all the work in most electric circuits , we still define a positive current as the direction a positive charge would move . this is a very old historical convention . can current be carried by positive charges ? yes . there are lots of examples . current is carried by both positive and negative charges in saltwater : if we put ordinary table salt in water , it becomes a good conductor . table salt is sodium chloride , nacl . the salt dissolves in water , into free-floating na $ ^+ $ and cl $ ^- $ ions . both ions respond to electric force and move through the saltwater solution , in opposite directions . in this case , the current is composed of moving atoms , both positive and negative ions , not just loose electrons . inside our bodies , electrical currents are moving ions , both positive and negative . the same definition of current works : count the number of charges passing by in a fixed amount of time . what causes current ? charged objects move in response to electric and magnetic forces . these forces come from electric and magnetic fields , which in turn come from the position and motion of other charges . what is the speed of current ? we do n't talk very often about the speed of current . answering the question , `` how fast is the current flowing ? '' requires understanding of a complex physical phenomenon and is not often relevant . current usually is n't about meters per second , it 's about charge per second . more often , we answer the question `` how much current is flowing ? '' all the time . how do we talk about current ? when discussing current , terms like through and in make a lot of sense . current flows through a resistor ; current flows in a wire . if you hear , `` the current across ... '' , it should sound odd . voltage to get our initial toehold on the concept of voltage , let 's look at an analogy : voltage resembles gravity for a mass $ m $ , a change of height $ h $ corresponds to a change in potential energy , $ \delta u = mg\delta h $ . for a charged particle $ q $ , a voltage $ v $ corresponds to a change in potential energy , $ \delta u = qv $ . voltage in an electric circuit is analogous to the product of $ g\cdot \delta h $ . where $ g $ is the acceleration due to gravity and $ \delta h $ is the change of height . a ball at the top of the hill rolls down . when it is halfway down , it has given up half of its potential energy . an electron at the top of a voltage `` hill '' travels `` downhill '' through wires and elements of a circuit . it gives up its potential energy , doing work along the way . when the electron is halfway down the hill , it has given up , or `` dropped '' , half of its potential energy . for both the ball and the electron , the trip down the hill happens spontaneously . the ball and electron move towards a lower energy state all by themselves . on the trip down , there can be things in the way of the ball , like trees or bears to bounce off . for electrons , we can guide electrons using wires and make them flow through electronic components —circuit design— and do interesting things along the way . we can express the voltage between two points mathematically as the change of energy experienced by a charge : $ v = \dfrac { \delta u } { q } $ that 's an intuitive description of voltage in a nutshell . power power is defined as the rate energy ( $ \text u $ ) is transformed or transferred over time . we measure power in units of joules/second , also known as watts . ( $ 1 \ , \text { watt } = 1\ , \text { joule } /\text { second } $ ) $ \text { power } = \dfrac { \text du } { \text dt } $ an electric circuit is capable of transferring power . current is the rate of flow of charge , and voltage measures the energy transferred per unit of charge . we can insert these definitions into the equation for power : $ \text { power } = \dfrac { \text du } { \text dt } = \dfrac { \text du } { \text dq } \cdot \dfrac { \text dq } { \text dt } = v \ , i $ electrical power is the product of voltage times current . in units of watts . summary these mental models for current and voltage will get us started on all sorts of interesting electric circuits . if you want to reach beyond this intuitive description of voltage you can read this more formal mathematical description of electric potential and voltage .
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we will create our first mental models for these basic electrical quantities . we will also talk about power , which is what happens when voltage and current act together . charge the concept of electricity arises from an observation of nature .
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how can i draw a chart with voltage , resistance and power ?
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voltage and current are the cornerstone concepts in electricity . we will create our first mental models for these basic electrical quantities . we will also talk about power , which is what happens when voltage and current act together . charge the concept of electricity arises from an observation of nature . we observe a force between objects , that , like gravity , acts at a distance . the source of this force has been given the name charge . a very noticeable thing about electric force is that it is large , far greater than the force of gravity . unlike gravity , however , there are two types of electric charge . opposite types of charge attract , and like types of charge repel . gravity has only one type : it only attracts , never repels . conductors and insulators conductors are made of atoms whose outer , or valence , electrons have relatively weak bonds to their nuclei , as shown in this fanciful image of a copper atom . when a bunch of metal atoms are together , they gladly share their outer electrons with each other , creating a `` swarm '' of electrons not associated with a particular nucleus . a very small electric force can make the electron swarm move . copper , gold , silver , and aluminum are good conductors . so is saltwater . there are also poor conductors . tungsten—a metal used for light bulb filaments—and carbon—used in graphite form in pencils—are relatively poor conductors because their electrons are less prone to move . insulators are materials whose outer electrons are tightly bound to their nuclei . modest electric forces are not able to pull these electrons free . when an electric force is applied , the electron clouds around the atom stretch and deform in response to the force , but the electrons do not depart . glass , plastic , stone , and air are insulators . even for insulators , though , electric force can always be turned up high enough to rip electrons away—this is called breakdown . that 's what is happening to air molecules when you see a spark . semiconductor materials fall between insulators and conductors . they usually act like insulators , but we can make them act like conductors under certain circumstances . the most well-known semiconductor material is silicon ( atomic number $ 14 $ ) . our ability to finely control the insulating and conducting properties of silicon allows us to create modern marvels like computers and mobile phones . the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current . current is reported as the number of charges per unit time passing through a boundary . visualize placing a boundary all the way through a wire . station yourself near the boundary and count the number of charges passing by . report how much charge passed through the boundary in one second . we assign a positive sign to current corresponding to the direction a positive charge would be moving . since current is the amount of charge passing through a boundary in a fixed amount of time , it can be expressed mathematically using the following equation : $ i = \dfrac { dq } { dt } $ that 's current in a nutshell . a few remarks on current what carries current in metal ? since electrons are free to move about in metals , moving electrons are what makes up the current in metals . the positive nuclei in metal atoms are fixed in place and do not contribute to current . even though electrons have a negative charge and do almost all the work in most electric circuits , we still define a positive current as the direction a positive charge would move . this is a very old historical convention . can current be carried by positive charges ? yes . there are lots of examples . current is carried by both positive and negative charges in saltwater : if we put ordinary table salt in water , it becomes a good conductor . table salt is sodium chloride , nacl . the salt dissolves in water , into free-floating na $ ^+ $ and cl $ ^- $ ions . both ions respond to electric force and move through the saltwater solution , in opposite directions . in this case , the current is composed of moving atoms , both positive and negative ions , not just loose electrons . inside our bodies , electrical currents are moving ions , both positive and negative . the same definition of current works : count the number of charges passing by in a fixed amount of time . what causes current ? charged objects move in response to electric and magnetic forces . these forces come from electric and magnetic fields , which in turn come from the position and motion of other charges . what is the speed of current ? we do n't talk very often about the speed of current . answering the question , `` how fast is the current flowing ? '' requires understanding of a complex physical phenomenon and is not often relevant . current usually is n't about meters per second , it 's about charge per second . more often , we answer the question `` how much current is flowing ? '' all the time . how do we talk about current ? when discussing current , terms like through and in make a lot of sense . current flows through a resistor ; current flows in a wire . if you hear , `` the current across ... '' , it should sound odd . voltage to get our initial toehold on the concept of voltage , let 's look at an analogy : voltage resembles gravity for a mass $ m $ , a change of height $ h $ corresponds to a change in potential energy , $ \delta u = mg\delta h $ . for a charged particle $ q $ , a voltage $ v $ corresponds to a change in potential energy , $ \delta u = qv $ . voltage in an electric circuit is analogous to the product of $ g\cdot \delta h $ . where $ g $ is the acceleration due to gravity and $ \delta h $ is the change of height . a ball at the top of the hill rolls down . when it is halfway down , it has given up half of its potential energy . an electron at the top of a voltage `` hill '' travels `` downhill '' through wires and elements of a circuit . it gives up its potential energy , doing work along the way . when the electron is halfway down the hill , it has given up , or `` dropped '' , half of its potential energy . for both the ball and the electron , the trip down the hill happens spontaneously . the ball and electron move towards a lower energy state all by themselves . on the trip down , there can be things in the way of the ball , like trees or bears to bounce off . for electrons , we can guide electrons using wires and make them flow through electronic components —circuit design— and do interesting things along the way . we can express the voltage between two points mathematically as the change of energy experienced by a charge : $ v = \dfrac { \delta u } { q } $ that 's an intuitive description of voltage in a nutshell . power power is defined as the rate energy ( $ \text u $ ) is transformed or transferred over time . we measure power in units of joules/second , also known as watts . ( $ 1 \ , \text { watt } = 1\ , \text { joule } /\text { second } $ ) $ \text { power } = \dfrac { \text du } { \text dt } $ an electric circuit is capable of transferring power . current is the rate of flow of charge , and voltage measures the energy transferred per unit of charge . we can insert these definitions into the equation for power : $ \text { power } = \dfrac { \text du } { \text dt } = \dfrac { \text du } { \text dq } \cdot \dfrac { \text dq } { \text dt } = v \ , i $ electrical power is the product of voltage times current . in units of watts . summary these mental models for current and voltage will get us started on all sorts of interesting electric circuits . if you want to reach beyond this intuitive description of voltage you can read this more formal mathematical description of electric potential and voltage .
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the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current .
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why does current flow the opposite direction of the flow of electrons ?
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voltage and current are the cornerstone concepts in electricity . we will create our first mental models for these basic electrical quantities . we will also talk about power , which is what happens when voltage and current act together . charge the concept of electricity arises from an observation of nature . we observe a force between objects , that , like gravity , acts at a distance . the source of this force has been given the name charge . a very noticeable thing about electric force is that it is large , far greater than the force of gravity . unlike gravity , however , there are two types of electric charge . opposite types of charge attract , and like types of charge repel . gravity has only one type : it only attracts , never repels . conductors and insulators conductors are made of atoms whose outer , or valence , electrons have relatively weak bonds to their nuclei , as shown in this fanciful image of a copper atom . when a bunch of metal atoms are together , they gladly share their outer electrons with each other , creating a `` swarm '' of electrons not associated with a particular nucleus . a very small electric force can make the electron swarm move . copper , gold , silver , and aluminum are good conductors . so is saltwater . there are also poor conductors . tungsten—a metal used for light bulb filaments—and carbon—used in graphite form in pencils—are relatively poor conductors because their electrons are less prone to move . insulators are materials whose outer electrons are tightly bound to their nuclei . modest electric forces are not able to pull these electrons free . when an electric force is applied , the electron clouds around the atom stretch and deform in response to the force , but the electrons do not depart . glass , plastic , stone , and air are insulators . even for insulators , though , electric force can always be turned up high enough to rip electrons away—this is called breakdown . that 's what is happening to air molecules when you see a spark . semiconductor materials fall between insulators and conductors . they usually act like insulators , but we can make them act like conductors under certain circumstances . the most well-known semiconductor material is silicon ( atomic number $ 14 $ ) . our ability to finely control the insulating and conducting properties of silicon allows us to create modern marvels like computers and mobile phones . the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current . current is reported as the number of charges per unit time passing through a boundary . visualize placing a boundary all the way through a wire . station yourself near the boundary and count the number of charges passing by . report how much charge passed through the boundary in one second . we assign a positive sign to current corresponding to the direction a positive charge would be moving . since current is the amount of charge passing through a boundary in a fixed amount of time , it can be expressed mathematically using the following equation : $ i = \dfrac { dq } { dt } $ that 's current in a nutshell . a few remarks on current what carries current in metal ? since electrons are free to move about in metals , moving electrons are what makes up the current in metals . the positive nuclei in metal atoms are fixed in place and do not contribute to current . even though electrons have a negative charge and do almost all the work in most electric circuits , we still define a positive current as the direction a positive charge would move . this is a very old historical convention . can current be carried by positive charges ? yes . there are lots of examples . current is carried by both positive and negative charges in saltwater : if we put ordinary table salt in water , it becomes a good conductor . table salt is sodium chloride , nacl . the salt dissolves in water , into free-floating na $ ^+ $ and cl $ ^- $ ions . both ions respond to electric force and move through the saltwater solution , in opposite directions . in this case , the current is composed of moving atoms , both positive and negative ions , not just loose electrons . inside our bodies , electrical currents are moving ions , both positive and negative . the same definition of current works : count the number of charges passing by in a fixed amount of time . what causes current ? charged objects move in response to electric and magnetic forces . these forces come from electric and magnetic fields , which in turn come from the position and motion of other charges . what is the speed of current ? we do n't talk very often about the speed of current . answering the question , `` how fast is the current flowing ? '' requires understanding of a complex physical phenomenon and is not often relevant . current usually is n't about meters per second , it 's about charge per second . more often , we answer the question `` how much current is flowing ? '' all the time . how do we talk about current ? when discussing current , terms like through and in make a lot of sense . current flows through a resistor ; current flows in a wire . if you hear , `` the current across ... '' , it should sound odd . voltage to get our initial toehold on the concept of voltage , let 's look at an analogy : voltage resembles gravity for a mass $ m $ , a change of height $ h $ corresponds to a change in potential energy , $ \delta u = mg\delta h $ . for a charged particle $ q $ , a voltage $ v $ corresponds to a change in potential energy , $ \delta u = qv $ . voltage in an electric circuit is analogous to the product of $ g\cdot \delta h $ . where $ g $ is the acceleration due to gravity and $ \delta h $ is the change of height . a ball at the top of the hill rolls down . when it is halfway down , it has given up half of its potential energy . an electron at the top of a voltage `` hill '' travels `` downhill '' through wires and elements of a circuit . it gives up its potential energy , doing work along the way . when the electron is halfway down the hill , it has given up , or `` dropped '' , half of its potential energy . for both the ball and the electron , the trip down the hill happens spontaneously . the ball and electron move towards a lower energy state all by themselves . on the trip down , there can be things in the way of the ball , like trees or bears to bounce off . for electrons , we can guide electrons using wires and make them flow through electronic components —circuit design— and do interesting things along the way . we can express the voltage between two points mathematically as the change of energy experienced by a charge : $ v = \dfrac { \delta u } { q } $ that 's an intuitive description of voltage in a nutshell . power power is defined as the rate energy ( $ \text u $ ) is transformed or transferred over time . we measure power in units of joules/second , also known as watts . ( $ 1 \ , \text { watt } = 1\ , \text { joule } /\text { second } $ ) $ \text { power } = \dfrac { \text du } { \text dt } $ an electric circuit is capable of transferring power . current is the rate of flow of charge , and voltage measures the energy transferred per unit of charge . we can insert these definitions into the equation for power : $ \text { power } = \dfrac { \text du } { \text dt } = \dfrac { \text du } { \text dq } \cdot \dfrac { \text dq } { \text dt } = v \ , i $ electrical power is the product of voltage times current . in units of watts . summary these mental models for current and voltage will get us started on all sorts of interesting electric circuits . if you want to reach beyond this intuitive description of voltage you can read this more formal mathematical description of electric potential and voltage .
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the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current .
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whould n't current flow be the same direction as the electrons ?
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voltage and current are the cornerstone concepts in electricity . we will create our first mental models for these basic electrical quantities . we will also talk about power , which is what happens when voltage and current act together . charge the concept of electricity arises from an observation of nature . we observe a force between objects , that , like gravity , acts at a distance . the source of this force has been given the name charge . a very noticeable thing about electric force is that it is large , far greater than the force of gravity . unlike gravity , however , there are two types of electric charge . opposite types of charge attract , and like types of charge repel . gravity has only one type : it only attracts , never repels . conductors and insulators conductors are made of atoms whose outer , or valence , electrons have relatively weak bonds to their nuclei , as shown in this fanciful image of a copper atom . when a bunch of metal atoms are together , they gladly share their outer electrons with each other , creating a `` swarm '' of electrons not associated with a particular nucleus . a very small electric force can make the electron swarm move . copper , gold , silver , and aluminum are good conductors . so is saltwater . there are also poor conductors . tungsten—a metal used for light bulb filaments—and carbon—used in graphite form in pencils—are relatively poor conductors because their electrons are less prone to move . insulators are materials whose outer electrons are tightly bound to their nuclei . modest electric forces are not able to pull these electrons free . when an electric force is applied , the electron clouds around the atom stretch and deform in response to the force , but the electrons do not depart . glass , plastic , stone , and air are insulators . even for insulators , though , electric force can always be turned up high enough to rip electrons away—this is called breakdown . that 's what is happening to air molecules when you see a spark . semiconductor materials fall between insulators and conductors . they usually act like insulators , but we can make them act like conductors under certain circumstances . the most well-known semiconductor material is silicon ( atomic number $ 14 $ ) . our ability to finely control the insulating and conducting properties of silicon allows us to create modern marvels like computers and mobile phones . the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current . current is reported as the number of charges per unit time passing through a boundary . visualize placing a boundary all the way through a wire . station yourself near the boundary and count the number of charges passing by . report how much charge passed through the boundary in one second . we assign a positive sign to current corresponding to the direction a positive charge would be moving . since current is the amount of charge passing through a boundary in a fixed amount of time , it can be expressed mathematically using the following equation : $ i = \dfrac { dq } { dt } $ that 's current in a nutshell . a few remarks on current what carries current in metal ? since electrons are free to move about in metals , moving electrons are what makes up the current in metals . the positive nuclei in metal atoms are fixed in place and do not contribute to current . even though electrons have a negative charge and do almost all the work in most electric circuits , we still define a positive current as the direction a positive charge would move . this is a very old historical convention . can current be carried by positive charges ? yes . there are lots of examples . current is carried by both positive and negative charges in saltwater : if we put ordinary table salt in water , it becomes a good conductor . table salt is sodium chloride , nacl . the salt dissolves in water , into free-floating na $ ^+ $ and cl $ ^- $ ions . both ions respond to electric force and move through the saltwater solution , in opposite directions . in this case , the current is composed of moving atoms , both positive and negative ions , not just loose electrons . inside our bodies , electrical currents are moving ions , both positive and negative . the same definition of current works : count the number of charges passing by in a fixed amount of time . what causes current ? charged objects move in response to electric and magnetic forces . these forces come from electric and magnetic fields , which in turn come from the position and motion of other charges . what is the speed of current ? we do n't talk very often about the speed of current . answering the question , `` how fast is the current flowing ? '' requires understanding of a complex physical phenomenon and is not often relevant . current usually is n't about meters per second , it 's about charge per second . more often , we answer the question `` how much current is flowing ? '' all the time . how do we talk about current ? when discussing current , terms like through and in make a lot of sense . current flows through a resistor ; current flows in a wire . if you hear , `` the current across ... '' , it should sound odd . voltage to get our initial toehold on the concept of voltage , let 's look at an analogy : voltage resembles gravity for a mass $ m $ , a change of height $ h $ corresponds to a change in potential energy , $ \delta u = mg\delta h $ . for a charged particle $ q $ , a voltage $ v $ corresponds to a change in potential energy , $ \delta u = qv $ . voltage in an electric circuit is analogous to the product of $ g\cdot \delta h $ . where $ g $ is the acceleration due to gravity and $ \delta h $ is the change of height . a ball at the top of the hill rolls down . when it is halfway down , it has given up half of its potential energy . an electron at the top of a voltage `` hill '' travels `` downhill '' through wires and elements of a circuit . it gives up its potential energy , doing work along the way . when the electron is halfway down the hill , it has given up , or `` dropped '' , half of its potential energy . for both the ball and the electron , the trip down the hill happens spontaneously . the ball and electron move towards a lower energy state all by themselves . on the trip down , there can be things in the way of the ball , like trees or bears to bounce off . for electrons , we can guide electrons using wires and make them flow through electronic components —circuit design— and do interesting things along the way . we can express the voltage between two points mathematically as the change of energy experienced by a charge : $ v = \dfrac { \delta u } { q } $ that 's an intuitive description of voltage in a nutshell . power power is defined as the rate energy ( $ \text u $ ) is transformed or transferred over time . we measure power in units of joules/second , also known as watts . ( $ 1 \ , \text { watt } = 1\ , \text { joule } /\text { second } $ ) $ \text { power } = \dfrac { \text du } { \text dt } $ an electric circuit is capable of transferring power . current is the rate of flow of charge , and voltage measures the energy transferred per unit of charge . we can insert these definitions into the equation for power : $ \text { power } = \dfrac { \text du } { \text dt } = \dfrac { \text du } { \text dq } \cdot \dfrac { \text dq } { \text dt } = v \ , i $ electrical power is the product of voltage times current . in units of watts . summary these mental models for current and voltage will get us started on all sorts of interesting electric circuits . if you want to reach beyond this intuitive description of voltage you can read this more formal mathematical description of electric potential and voltage .
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inside our bodies , electrical currents are moving ions , both positive and negative . the same definition of current works : count the number of charges passing by in a fixed amount of time . what causes current ?
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how does an alternator works ?
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voltage and current are the cornerstone concepts in electricity . we will create our first mental models for these basic electrical quantities . we will also talk about power , which is what happens when voltage and current act together . charge the concept of electricity arises from an observation of nature . we observe a force between objects , that , like gravity , acts at a distance . the source of this force has been given the name charge . a very noticeable thing about electric force is that it is large , far greater than the force of gravity . unlike gravity , however , there are two types of electric charge . opposite types of charge attract , and like types of charge repel . gravity has only one type : it only attracts , never repels . conductors and insulators conductors are made of atoms whose outer , or valence , electrons have relatively weak bonds to their nuclei , as shown in this fanciful image of a copper atom . when a bunch of metal atoms are together , they gladly share their outer electrons with each other , creating a `` swarm '' of electrons not associated with a particular nucleus . a very small electric force can make the electron swarm move . copper , gold , silver , and aluminum are good conductors . so is saltwater . there are also poor conductors . tungsten—a metal used for light bulb filaments—and carbon—used in graphite form in pencils—are relatively poor conductors because their electrons are less prone to move . insulators are materials whose outer electrons are tightly bound to their nuclei . modest electric forces are not able to pull these electrons free . when an electric force is applied , the electron clouds around the atom stretch and deform in response to the force , but the electrons do not depart . glass , plastic , stone , and air are insulators . even for insulators , though , electric force can always be turned up high enough to rip electrons away—this is called breakdown . that 's what is happening to air molecules when you see a spark . semiconductor materials fall between insulators and conductors . they usually act like insulators , but we can make them act like conductors under certain circumstances . the most well-known semiconductor material is silicon ( atomic number $ 14 $ ) . our ability to finely control the insulating and conducting properties of silicon allows us to create modern marvels like computers and mobile phones . the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current . current is reported as the number of charges per unit time passing through a boundary . visualize placing a boundary all the way through a wire . station yourself near the boundary and count the number of charges passing by . report how much charge passed through the boundary in one second . we assign a positive sign to current corresponding to the direction a positive charge would be moving . since current is the amount of charge passing through a boundary in a fixed amount of time , it can be expressed mathematically using the following equation : $ i = \dfrac { dq } { dt } $ that 's current in a nutshell . a few remarks on current what carries current in metal ? since electrons are free to move about in metals , moving electrons are what makes up the current in metals . the positive nuclei in metal atoms are fixed in place and do not contribute to current . even though electrons have a negative charge and do almost all the work in most electric circuits , we still define a positive current as the direction a positive charge would move . this is a very old historical convention . can current be carried by positive charges ? yes . there are lots of examples . current is carried by both positive and negative charges in saltwater : if we put ordinary table salt in water , it becomes a good conductor . table salt is sodium chloride , nacl . the salt dissolves in water , into free-floating na $ ^+ $ and cl $ ^- $ ions . both ions respond to electric force and move through the saltwater solution , in opposite directions . in this case , the current is composed of moving atoms , both positive and negative ions , not just loose electrons . inside our bodies , electrical currents are moving ions , both positive and negative . the same definition of current works : count the number of charges passing by in a fixed amount of time . what causes current ? charged objects move in response to electric and magnetic forces . these forces come from electric and magnetic fields , which in turn come from the position and motion of other charges . what is the speed of current ? we do n't talk very often about the speed of current . answering the question , `` how fast is the current flowing ? '' requires understanding of a complex physical phenomenon and is not often relevant . current usually is n't about meters per second , it 's about charge per second . more often , we answer the question `` how much current is flowing ? '' all the time . how do we talk about current ? when discussing current , terms like through and in make a lot of sense . current flows through a resistor ; current flows in a wire . if you hear , `` the current across ... '' , it should sound odd . voltage to get our initial toehold on the concept of voltage , let 's look at an analogy : voltage resembles gravity for a mass $ m $ , a change of height $ h $ corresponds to a change in potential energy , $ \delta u = mg\delta h $ . for a charged particle $ q $ , a voltage $ v $ corresponds to a change in potential energy , $ \delta u = qv $ . voltage in an electric circuit is analogous to the product of $ g\cdot \delta h $ . where $ g $ is the acceleration due to gravity and $ \delta h $ is the change of height . a ball at the top of the hill rolls down . when it is halfway down , it has given up half of its potential energy . an electron at the top of a voltage `` hill '' travels `` downhill '' through wires and elements of a circuit . it gives up its potential energy , doing work along the way . when the electron is halfway down the hill , it has given up , or `` dropped '' , half of its potential energy . for both the ball and the electron , the trip down the hill happens spontaneously . the ball and electron move towards a lower energy state all by themselves . on the trip down , there can be things in the way of the ball , like trees or bears to bounce off . for electrons , we can guide electrons using wires and make them flow through electronic components —circuit design— and do interesting things along the way . we can express the voltage between two points mathematically as the change of energy experienced by a charge : $ v = \dfrac { \delta u } { q } $ that 's an intuitive description of voltage in a nutshell . power power is defined as the rate energy ( $ \text u $ ) is transformed or transferred over time . we measure power in units of joules/second , also known as watts . ( $ 1 \ , \text { watt } = 1\ , \text { joule } /\text { second } $ ) $ \text { power } = \dfrac { \text du } { \text dt } $ an electric circuit is capable of transferring power . current is the rate of flow of charge , and voltage measures the energy transferred per unit of charge . we can insert these definitions into the equation for power : $ \text { power } = \dfrac { \text du } { \text dt } = \dfrac { \text du } { \text dq } \cdot \dfrac { \text dq } { \text dt } = v \ , i $ electrical power is the product of voltage times current . in units of watts . summary these mental models for current and voltage will get us started on all sorts of interesting electric circuits . if you want to reach beyond this intuitive description of voltage you can read this more formal mathematical description of electric potential and voltage .
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this is a very old historical convention . can current be carried by positive charges ? yes .
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what is the positive charges ?
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voltage and current are the cornerstone concepts in electricity . we will create our first mental models for these basic electrical quantities . we will also talk about power , which is what happens when voltage and current act together . charge the concept of electricity arises from an observation of nature . we observe a force between objects , that , like gravity , acts at a distance . the source of this force has been given the name charge . a very noticeable thing about electric force is that it is large , far greater than the force of gravity . unlike gravity , however , there are two types of electric charge . opposite types of charge attract , and like types of charge repel . gravity has only one type : it only attracts , never repels . conductors and insulators conductors are made of atoms whose outer , or valence , electrons have relatively weak bonds to their nuclei , as shown in this fanciful image of a copper atom . when a bunch of metal atoms are together , they gladly share their outer electrons with each other , creating a `` swarm '' of electrons not associated with a particular nucleus . a very small electric force can make the electron swarm move . copper , gold , silver , and aluminum are good conductors . so is saltwater . there are also poor conductors . tungsten—a metal used for light bulb filaments—and carbon—used in graphite form in pencils—are relatively poor conductors because their electrons are less prone to move . insulators are materials whose outer electrons are tightly bound to their nuclei . modest electric forces are not able to pull these electrons free . when an electric force is applied , the electron clouds around the atom stretch and deform in response to the force , but the electrons do not depart . glass , plastic , stone , and air are insulators . even for insulators , though , electric force can always be turned up high enough to rip electrons away—this is called breakdown . that 's what is happening to air molecules when you see a spark . semiconductor materials fall between insulators and conductors . they usually act like insulators , but we can make them act like conductors under certain circumstances . the most well-known semiconductor material is silicon ( atomic number $ 14 $ ) . our ability to finely control the insulating and conducting properties of silicon allows us to create modern marvels like computers and mobile phones . the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current . current is reported as the number of charges per unit time passing through a boundary . visualize placing a boundary all the way through a wire . station yourself near the boundary and count the number of charges passing by . report how much charge passed through the boundary in one second . we assign a positive sign to current corresponding to the direction a positive charge would be moving . since current is the amount of charge passing through a boundary in a fixed amount of time , it can be expressed mathematically using the following equation : $ i = \dfrac { dq } { dt } $ that 's current in a nutshell . a few remarks on current what carries current in metal ? since electrons are free to move about in metals , moving electrons are what makes up the current in metals . the positive nuclei in metal atoms are fixed in place and do not contribute to current . even though electrons have a negative charge and do almost all the work in most electric circuits , we still define a positive current as the direction a positive charge would move . this is a very old historical convention . can current be carried by positive charges ? yes . there are lots of examples . current is carried by both positive and negative charges in saltwater : if we put ordinary table salt in water , it becomes a good conductor . table salt is sodium chloride , nacl . the salt dissolves in water , into free-floating na $ ^+ $ and cl $ ^- $ ions . both ions respond to electric force and move through the saltwater solution , in opposite directions . in this case , the current is composed of moving atoms , both positive and negative ions , not just loose electrons . inside our bodies , electrical currents are moving ions , both positive and negative . the same definition of current works : count the number of charges passing by in a fixed amount of time . what causes current ? charged objects move in response to electric and magnetic forces . these forces come from electric and magnetic fields , which in turn come from the position and motion of other charges . what is the speed of current ? we do n't talk very often about the speed of current . answering the question , `` how fast is the current flowing ? '' requires understanding of a complex physical phenomenon and is not often relevant . current usually is n't about meters per second , it 's about charge per second . more often , we answer the question `` how much current is flowing ? '' all the time . how do we talk about current ? when discussing current , terms like through and in make a lot of sense . current flows through a resistor ; current flows in a wire . if you hear , `` the current across ... '' , it should sound odd . voltage to get our initial toehold on the concept of voltage , let 's look at an analogy : voltage resembles gravity for a mass $ m $ , a change of height $ h $ corresponds to a change in potential energy , $ \delta u = mg\delta h $ . for a charged particle $ q $ , a voltage $ v $ corresponds to a change in potential energy , $ \delta u = qv $ . voltage in an electric circuit is analogous to the product of $ g\cdot \delta h $ . where $ g $ is the acceleration due to gravity and $ \delta h $ is the change of height . a ball at the top of the hill rolls down . when it is halfway down , it has given up half of its potential energy . an electron at the top of a voltage `` hill '' travels `` downhill '' through wires and elements of a circuit . it gives up its potential energy , doing work along the way . when the electron is halfway down the hill , it has given up , or `` dropped '' , half of its potential energy . for both the ball and the electron , the trip down the hill happens spontaneously . the ball and electron move towards a lower energy state all by themselves . on the trip down , there can be things in the way of the ball , like trees or bears to bounce off . for electrons , we can guide electrons using wires and make them flow through electronic components —circuit design— and do interesting things along the way . we can express the voltage between two points mathematically as the change of energy experienced by a charge : $ v = \dfrac { \delta u } { q } $ that 's an intuitive description of voltage in a nutshell . power power is defined as the rate energy ( $ \text u $ ) is transformed or transferred over time . we measure power in units of joules/second , also known as watts . ( $ 1 \ , \text { watt } = 1\ , \text { joule } /\text { second } $ ) $ \text { power } = \dfrac { \text du } { \text dt } $ an electric circuit is capable of transferring power . current is the rate of flow of charge , and voltage measures the energy transferred per unit of charge . we can insert these definitions into the equation for power : $ \text { power } = \dfrac { \text du } { \text dt } = \dfrac { \text du } { \text dq } \cdot \dfrac { \text dq } { \text dt } = v \ , i $ electrical power is the product of voltage times current . in units of watts . summary these mental models for current and voltage will get us started on all sorts of interesting electric circuits . if you want to reach beyond this intuitive description of voltage you can read this more formal mathematical description of electric potential and voltage .
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summary these mental models for current and voltage will get us started on all sorts of interesting electric circuits . if you want to reach beyond this intuitive description of voltage you can read this more formal mathematical description of electric potential and voltage .
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is there any difference between voltage and potential difference ?
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voltage and current are the cornerstone concepts in electricity . we will create our first mental models for these basic electrical quantities . we will also talk about power , which is what happens when voltage and current act together . charge the concept of electricity arises from an observation of nature . we observe a force between objects , that , like gravity , acts at a distance . the source of this force has been given the name charge . a very noticeable thing about electric force is that it is large , far greater than the force of gravity . unlike gravity , however , there are two types of electric charge . opposite types of charge attract , and like types of charge repel . gravity has only one type : it only attracts , never repels . conductors and insulators conductors are made of atoms whose outer , or valence , electrons have relatively weak bonds to their nuclei , as shown in this fanciful image of a copper atom . when a bunch of metal atoms are together , they gladly share their outer electrons with each other , creating a `` swarm '' of electrons not associated with a particular nucleus . a very small electric force can make the electron swarm move . copper , gold , silver , and aluminum are good conductors . so is saltwater . there are also poor conductors . tungsten—a metal used for light bulb filaments—and carbon—used in graphite form in pencils—are relatively poor conductors because their electrons are less prone to move . insulators are materials whose outer electrons are tightly bound to their nuclei . modest electric forces are not able to pull these electrons free . when an electric force is applied , the electron clouds around the atom stretch and deform in response to the force , but the electrons do not depart . glass , plastic , stone , and air are insulators . even for insulators , though , electric force can always be turned up high enough to rip electrons away—this is called breakdown . that 's what is happening to air molecules when you see a spark . semiconductor materials fall between insulators and conductors . they usually act like insulators , but we can make them act like conductors under certain circumstances . the most well-known semiconductor material is silicon ( atomic number $ 14 $ ) . our ability to finely control the insulating and conducting properties of silicon allows us to create modern marvels like computers and mobile phones . the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current . current is reported as the number of charges per unit time passing through a boundary . visualize placing a boundary all the way through a wire . station yourself near the boundary and count the number of charges passing by . report how much charge passed through the boundary in one second . we assign a positive sign to current corresponding to the direction a positive charge would be moving . since current is the amount of charge passing through a boundary in a fixed amount of time , it can be expressed mathematically using the following equation : $ i = \dfrac { dq } { dt } $ that 's current in a nutshell . a few remarks on current what carries current in metal ? since electrons are free to move about in metals , moving electrons are what makes up the current in metals . the positive nuclei in metal atoms are fixed in place and do not contribute to current . even though electrons have a negative charge and do almost all the work in most electric circuits , we still define a positive current as the direction a positive charge would move . this is a very old historical convention . can current be carried by positive charges ? yes . there are lots of examples . current is carried by both positive and negative charges in saltwater : if we put ordinary table salt in water , it becomes a good conductor . table salt is sodium chloride , nacl . the salt dissolves in water , into free-floating na $ ^+ $ and cl $ ^- $ ions . both ions respond to electric force and move through the saltwater solution , in opposite directions . in this case , the current is composed of moving atoms , both positive and negative ions , not just loose electrons . inside our bodies , electrical currents are moving ions , both positive and negative . the same definition of current works : count the number of charges passing by in a fixed amount of time . what causes current ? charged objects move in response to electric and magnetic forces . these forces come from electric and magnetic fields , which in turn come from the position and motion of other charges . what is the speed of current ? we do n't talk very often about the speed of current . answering the question , `` how fast is the current flowing ? '' requires understanding of a complex physical phenomenon and is not often relevant . current usually is n't about meters per second , it 's about charge per second . more often , we answer the question `` how much current is flowing ? '' all the time . how do we talk about current ? when discussing current , terms like through and in make a lot of sense . current flows through a resistor ; current flows in a wire . if you hear , `` the current across ... '' , it should sound odd . voltage to get our initial toehold on the concept of voltage , let 's look at an analogy : voltage resembles gravity for a mass $ m $ , a change of height $ h $ corresponds to a change in potential energy , $ \delta u = mg\delta h $ . for a charged particle $ q $ , a voltage $ v $ corresponds to a change in potential energy , $ \delta u = qv $ . voltage in an electric circuit is analogous to the product of $ g\cdot \delta h $ . where $ g $ is the acceleration due to gravity and $ \delta h $ is the change of height . a ball at the top of the hill rolls down . when it is halfway down , it has given up half of its potential energy . an electron at the top of a voltage `` hill '' travels `` downhill '' through wires and elements of a circuit . it gives up its potential energy , doing work along the way . when the electron is halfway down the hill , it has given up , or `` dropped '' , half of its potential energy . for both the ball and the electron , the trip down the hill happens spontaneously . the ball and electron move towards a lower energy state all by themselves . on the trip down , there can be things in the way of the ball , like trees or bears to bounce off . for electrons , we can guide electrons using wires and make them flow through electronic components —circuit design— and do interesting things along the way . we can express the voltage between two points mathematically as the change of energy experienced by a charge : $ v = \dfrac { \delta u } { q } $ that 's an intuitive description of voltage in a nutshell . power power is defined as the rate energy ( $ \text u $ ) is transformed or transferred over time . we measure power in units of joules/second , also known as watts . ( $ 1 \ , \text { watt } = 1\ , \text { joule } /\text { second } $ ) $ \text { power } = \dfrac { \text du } { \text dt } $ an electric circuit is capable of transferring power . current is the rate of flow of charge , and voltage measures the energy transferred per unit of charge . we can insert these definitions into the equation for power : $ \text { power } = \dfrac { \text du } { \text dt } = \dfrac { \text du } { \text dq } \cdot \dfrac { \text dq } { \text dt } = v \ , i $ electrical power is the product of voltage times current . in units of watts . summary these mental models for current and voltage will get us started on all sorts of interesting electric circuits . if you want to reach beyond this intuitive description of voltage you can read this more formal mathematical description of electric potential and voltage .
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glass , plastic , stone , and air are insulators . even for insulators , though , electric force can always be turned up high enough to rip electrons away—this is called breakdown . that 's what is happening to air molecules when you see a spark .
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why ammeter is always connected in series and voltmeter is always connected parellely ?
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voltage and current are the cornerstone concepts in electricity . we will create our first mental models for these basic electrical quantities . we will also talk about power , which is what happens when voltage and current act together . charge the concept of electricity arises from an observation of nature . we observe a force between objects , that , like gravity , acts at a distance . the source of this force has been given the name charge . a very noticeable thing about electric force is that it is large , far greater than the force of gravity . unlike gravity , however , there are two types of electric charge . opposite types of charge attract , and like types of charge repel . gravity has only one type : it only attracts , never repels . conductors and insulators conductors are made of atoms whose outer , or valence , electrons have relatively weak bonds to their nuclei , as shown in this fanciful image of a copper atom . when a bunch of metal atoms are together , they gladly share their outer electrons with each other , creating a `` swarm '' of electrons not associated with a particular nucleus . a very small electric force can make the electron swarm move . copper , gold , silver , and aluminum are good conductors . so is saltwater . there are also poor conductors . tungsten—a metal used for light bulb filaments—and carbon—used in graphite form in pencils—are relatively poor conductors because their electrons are less prone to move . insulators are materials whose outer electrons are tightly bound to their nuclei . modest electric forces are not able to pull these electrons free . when an electric force is applied , the electron clouds around the atom stretch and deform in response to the force , but the electrons do not depart . glass , plastic , stone , and air are insulators . even for insulators , though , electric force can always be turned up high enough to rip electrons away—this is called breakdown . that 's what is happening to air molecules when you see a spark . semiconductor materials fall between insulators and conductors . they usually act like insulators , but we can make them act like conductors under certain circumstances . the most well-known semiconductor material is silicon ( atomic number $ 14 $ ) . our ability to finely control the insulating and conducting properties of silicon allows us to create modern marvels like computers and mobile phones . the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current . current is reported as the number of charges per unit time passing through a boundary . visualize placing a boundary all the way through a wire . station yourself near the boundary and count the number of charges passing by . report how much charge passed through the boundary in one second . we assign a positive sign to current corresponding to the direction a positive charge would be moving . since current is the amount of charge passing through a boundary in a fixed amount of time , it can be expressed mathematically using the following equation : $ i = \dfrac { dq } { dt } $ that 's current in a nutshell . a few remarks on current what carries current in metal ? since electrons are free to move about in metals , moving electrons are what makes up the current in metals . the positive nuclei in metal atoms are fixed in place and do not contribute to current . even though electrons have a negative charge and do almost all the work in most electric circuits , we still define a positive current as the direction a positive charge would move . this is a very old historical convention . can current be carried by positive charges ? yes . there are lots of examples . current is carried by both positive and negative charges in saltwater : if we put ordinary table salt in water , it becomes a good conductor . table salt is sodium chloride , nacl . the salt dissolves in water , into free-floating na $ ^+ $ and cl $ ^- $ ions . both ions respond to electric force and move through the saltwater solution , in opposite directions . in this case , the current is composed of moving atoms , both positive and negative ions , not just loose electrons . inside our bodies , electrical currents are moving ions , both positive and negative . the same definition of current works : count the number of charges passing by in a fixed amount of time . what causes current ? charged objects move in response to electric and magnetic forces . these forces come from electric and magnetic fields , which in turn come from the position and motion of other charges . what is the speed of current ? we do n't talk very often about the speed of current . answering the question , `` how fast is the current flowing ? '' requires understanding of a complex physical phenomenon and is not often relevant . current usually is n't about meters per second , it 's about charge per second . more often , we answer the question `` how much current is flowing ? '' all the time . how do we talk about current ? when discussing current , terms like through and in make a lot of sense . current flows through a resistor ; current flows in a wire . if you hear , `` the current across ... '' , it should sound odd . voltage to get our initial toehold on the concept of voltage , let 's look at an analogy : voltage resembles gravity for a mass $ m $ , a change of height $ h $ corresponds to a change in potential energy , $ \delta u = mg\delta h $ . for a charged particle $ q $ , a voltage $ v $ corresponds to a change in potential energy , $ \delta u = qv $ . voltage in an electric circuit is analogous to the product of $ g\cdot \delta h $ . where $ g $ is the acceleration due to gravity and $ \delta h $ is the change of height . a ball at the top of the hill rolls down . when it is halfway down , it has given up half of its potential energy . an electron at the top of a voltage `` hill '' travels `` downhill '' through wires and elements of a circuit . it gives up its potential energy , doing work along the way . when the electron is halfway down the hill , it has given up , or `` dropped '' , half of its potential energy . for both the ball and the electron , the trip down the hill happens spontaneously . the ball and electron move towards a lower energy state all by themselves . on the trip down , there can be things in the way of the ball , like trees or bears to bounce off . for electrons , we can guide electrons using wires and make them flow through electronic components —circuit design— and do interesting things along the way . we can express the voltage between two points mathematically as the change of energy experienced by a charge : $ v = \dfrac { \delta u } { q } $ that 's an intuitive description of voltage in a nutshell . power power is defined as the rate energy ( $ \text u $ ) is transformed or transferred over time . we measure power in units of joules/second , also known as watts . ( $ 1 \ , \text { watt } = 1\ , \text { joule } /\text { second } $ ) $ \text { power } = \dfrac { \text du } { \text dt } $ an electric circuit is capable of transferring power . current is the rate of flow of charge , and voltage measures the energy transferred per unit of charge . we can insert these definitions into the equation for power : $ \text { power } = \dfrac { \text du } { \text dt } = \dfrac { \text du } { \text dq } \cdot \dfrac { \text dq } { \text dt } = v \ , i $ electrical power is the product of voltage times current . in units of watts . summary these mental models for current and voltage will get us started on all sorts of interesting electric circuits . if you want to reach beyond this intuitive description of voltage you can read this more formal mathematical description of electric potential and voltage .
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voltage and current are the cornerstone concepts in electricity . we will create our first mental models for these basic electrical quantities .
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what is the difference between rheostat and variable resistance ?
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voltage and current are the cornerstone concepts in electricity . we will create our first mental models for these basic electrical quantities . we will also talk about power , which is what happens when voltage and current act together . charge the concept of electricity arises from an observation of nature . we observe a force between objects , that , like gravity , acts at a distance . the source of this force has been given the name charge . a very noticeable thing about electric force is that it is large , far greater than the force of gravity . unlike gravity , however , there are two types of electric charge . opposite types of charge attract , and like types of charge repel . gravity has only one type : it only attracts , never repels . conductors and insulators conductors are made of atoms whose outer , or valence , electrons have relatively weak bonds to their nuclei , as shown in this fanciful image of a copper atom . when a bunch of metal atoms are together , they gladly share their outer electrons with each other , creating a `` swarm '' of electrons not associated with a particular nucleus . a very small electric force can make the electron swarm move . copper , gold , silver , and aluminum are good conductors . so is saltwater . there are also poor conductors . tungsten—a metal used for light bulb filaments—and carbon—used in graphite form in pencils—are relatively poor conductors because their electrons are less prone to move . insulators are materials whose outer electrons are tightly bound to their nuclei . modest electric forces are not able to pull these electrons free . when an electric force is applied , the electron clouds around the atom stretch and deform in response to the force , but the electrons do not depart . glass , plastic , stone , and air are insulators . even for insulators , though , electric force can always be turned up high enough to rip electrons away—this is called breakdown . that 's what is happening to air molecules when you see a spark . semiconductor materials fall between insulators and conductors . they usually act like insulators , but we can make them act like conductors under certain circumstances . the most well-known semiconductor material is silicon ( atomic number $ 14 $ ) . our ability to finely control the insulating and conducting properties of silicon allows us to create modern marvels like computers and mobile phones . the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current . current is reported as the number of charges per unit time passing through a boundary . visualize placing a boundary all the way through a wire . station yourself near the boundary and count the number of charges passing by . report how much charge passed through the boundary in one second . we assign a positive sign to current corresponding to the direction a positive charge would be moving . since current is the amount of charge passing through a boundary in a fixed amount of time , it can be expressed mathematically using the following equation : $ i = \dfrac { dq } { dt } $ that 's current in a nutshell . a few remarks on current what carries current in metal ? since electrons are free to move about in metals , moving electrons are what makes up the current in metals . the positive nuclei in metal atoms are fixed in place and do not contribute to current . even though electrons have a negative charge and do almost all the work in most electric circuits , we still define a positive current as the direction a positive charge would move . this is a very old historical convention . can current be carried by positive charges ? yes . there are lots of examples . current is carried by both positive and negative charges in saltwater : if we put ordinary table salt in water , it becomes a good conductor . table salt is sodium chloride , nacl . the salt dissolves in water , into free-floating na $ ^+ $ and cl $ ^- $ ions . both ions respond to electric force and move through the saltwater solution , in opposite directions . in this case , the current is composed of moving atoms , both positive and negative ions , not just loose electrons . inside our bodies , electrical currents are moving ions , both positive and negative . the same definition of current works : count the number of charges passing by in a fixed amount of time . what causes current ? charged objects move in response to electric and magnetic forces . these forces come from electric and magnetic fields , which in turn come from the position and motion of other charges . what is the speed of current ? we do n't talk very often about the speed of current . answering the question , `` how fast is the current flowing ? '' requires understanding of a complex physical phenomenon and is not often relevant . current usually is n't about meters per second , it 's about charge per second . more often , we answer the question `` how much current is flowing ? '' all the time . how do we talk about current ? when discussing current , terms like through and in make a lot of sense . current flows through a resistor ; current flows in a wire . if you hear , `` the current across ... '' , it should sound odd . voltage to get our initial toehold on the concept of voltage , let 's look at an analogy : voltage resembles gravity for a mass $ m $ , a change of height $ h $ corresponds to a change in potential energy , $ \delta u = mg\delta h $ . for a charged particle $ q $ , a voltage $ v $ corresponds to a change in potential energy , $ \delta u = qv $ . voltage in an electric circuit is analogous to the product of $ g\cdot \delta h $ . where $ g $ is the acceleration due to gravity and $ \delta h $ is the change of height . a ball at the top of the hill rolls down . when it is halfway down , it has given up half of its potential energy . an electron at the top of a voltage `` hill '' travels `` downhill '' through wires and elements of a circuit . it gives up its potential energy , doing work along the way . when the electron is halfway down the hill , it has given up , or `` dropped '' , half of its potential energy . for both the ball and the electron , the trip down the hill happens spontaneously . the ball and electron move towards a lower energy state all by themselves . on the trip down , there can be things in the way of the ball , like trees or bears to bounce off . for electrons , we can guide electrons using wires and make them flow through electronic components —circuit design— and do interesting things along the way . we can express the voltage between two points mathematically as the change of energy experienced by a charge : $ v = \dfrac { \delta u } { q } $ that 's an intuitive description of voltage in a nutshell . power power is defined as the rate energy ( $ \text u $ ) is transformed or transferred over time . we measure power in units of joules/second , also known as watts . ( $ 1 \ , \text { watt } = 1\ , \text { joule } /\text { second } $ ) $ \text { power } = \dfrac { \text du } { \text dt } $ an electric circuit is capable of transferring power . current is the rate of flow of charge , and voltage measures the energy transferred per unit of charge . we can insert these definitions into the equation for power : $ \text { power } = \dfrac { \text du } { \text dt } = \dfrac { \text du } { \text dq } \cdot \dfrac { \text dq } { \text dt } = v \ , i $ electrical power is the product of voltage times current . in units of watts . summary these mental models for current and voltage will get us started on all sorts of interesting electric circuits . if you want to reach beyond this intuitive description of voltage you can read this more formal mathematical description of electric potential and voltage .
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both ions respond to electric force and move through the saltwater solution , in opposite directions . in this case , the current is composed of moving atoms , both positive and negative ions , not just loose electrons . inside our bodies , electrical currents are moving ions , both positive and negative .
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why in the case of refraction , when incident ray falls on the normal it deflects back at 0degree ?
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voltage and current are the cornerstone concepts in electricity . we will create our first mental models for these basic electrical quantities . we will also talk about power , which is what happens when voltage and current act together . charge the concept of electricity arises from an observation of nature . we observe a force between objects , that , like gravity , acts at a distance . the source of this force has been given the name charge . a very noticeable thing about electric force is that it is large , far greater than the force of gravity . unlike gravity , however , there are two types of electric charge . opposite types of charge attract , and like types of charge repel . gravity has only one type : it only attracts , never repels . conductors and insulators conductors are made of atoms whose outer , or valence , electrons have relatively weak bonds to their nuclei , as shown in this fanciful image of a copper atom . when a bunch of metal atoms are together , they gladly share their outer electrons with each other , creating a `` swarm '' of electrons not associated with a particular nucleus . a very small electric force can make the electron swarm move . copper , gold , silver , and aluminum are good conductors . so is saltwater . there are also poor conductors . tungsten—a metal used for light bulb filaments—and carbon—used in graphite form in pencils—are relatively poor conductors because their electrons are less prone to move . insulators are materials whose outer electrons are tightly bound to their nuclei . modest electric forces are not able to pull these electrons free . when an electric force is applied , the electron clouds around the atom stretch and deform in response to the force , but the electrons do not depart . glass , plastic , stone , and air are insulators . even for insulators , though , electric force can always be turned up high enough to rip electrons away—this is called breakdown . that 's what is happening to air molecules when you see a spark . semiconductor materials fall between insulators and conductors . they usually act like insulators , but we can make them act like conductors under certain circumstances . the most well-known semiconductor material is silicon ( atomic number $ 14 $ ) . our ability to finely control the insulating and conducting properties of silicon allows us to create modern marvels like computers and mobile phones . the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current . current is reported as the number of charges per unit time passing through a boundary . visualize placing a boundary all the way through a wire . station yourself near the boundary and count the number of charges passing by . report how much charge passed through the boundary in one second . we assign a positive sign to current corresponding to the direction a positive charge would be moving . since current is the amount of charge passing through a boundary in a fixed amount of time , it can be expressed mathematically using the following equation : $ i = \dfrac { dq } { dt } $ that 's current in a nutshell . a few remarks on current what carries current in metal ? since electrons are free to move about in metals , moving electrons are what makes up the current in metals . the positive nuclei in metal atoms are fixed in place and do not contribute to current . even though electrons have a negative charge and do almost all the work in most electric circuits , we still define a positive current as the direction a positive charge would move . this is a very old historical convention . can current be carried by positive charges ? yes . there are lots of examples . current is carried by both positive and negative charges in saltwater : if we put ordinary table salt in water , it becomes a good conductor . table salt is sodium chloride , nacl . the salt dissolves in water , into free-floating na $ ^+ $ and cl $ ^- $ ions . both ions respond to electric force and move through the saltwater solution , in opposite directions . in this case , the current is composed of moving atoms , both positive and negative ions , not just loose electrons . inside our bodies , electrical currents are moving ions , both positive and negative . the same definition of current works : count the number of charges passing by in a fixed amount of time . what causes current ? charged objects move in response to electric and magnetic forces . these forces come from electric and magnetic fields , which in turn come from the position and motion of other charges . what is the speed of current ? we do n't talk very often about the speed of current . answering the question , `` how fast is the current flowing ? '' requires understanding of a complex physical phenomenon and is not often relevant . current usually is n't about meters per second , it 's about charge per second . more often , we answer the question `` how much current is flowing ? '' all the time . how do we talk about current ? when discussing current , terms like through and in make a lot of sense . current flows through a resistor ; current flows in a wire . if you hear , `` the current across ... '' , it should sound odd . voltage to get our initial toehold on the concept of voltage , let 's look at an analogy : voltage resembles gravity for a mass $ m $ , a change of height $ h $ corresponds to a change in potential energy , $ \delta u = mg\delta h $ . for a charged particle $ q $ , a voltage $ v $ corresponds to a change in potential energy , $ \delta u = qv $ . voltage in an electric circuit is analogous to the product of $ g\cdot \delta h $ . where $ g $ is the acceleration due to gravity and $ \delta h $ is the change of height . a ball at the top of the hill rolls down . when it is halfway down , it has given up half of its potential energy . an electron at the top of a voltage `` hill '' travels `` downhill '' through wires and elements of a circuit . it gives up its potential energy , doing work along the way . when the electron is halfway down the hill , it has given up , or `` dropped '' , half of its potential energy . for both the ball and the electron , the trip down the hill happens spontaneously . the ball and electron move towards a lower energy state all by themselves . on the trip down , there can be things in the way of the ball , like trees or bears to bounce off . for electrons , we can guide electrons using wires and make them flow through electronic components —circuit design— and do interesting things along the way . we can express the voltage between two points mathematically as the change of energy experienced by a charge : $ v = \dfrac { \delta u } { q } $ that 's an intuitive description of voltage in a nutshell . power power is defined as the rate energy ( $ \text u $ ) is transformed or transferred over time . we measure power in units of joules/second , also known as watts . ( $ 1 \ , \text { watt } = 1\ , \text { joule } /\text { second } $ ) $ \text { power } = \dfrac { \text du } { \text dt } $ an electric circuit is capable of transferring power . current is the rate of flow of charge , and voltage measures the energy transferred per unit of charge . we can insert these definitions into the equation for power : $ \text { power } = \dfrac { \text du } { \text dt } = \dfrac { \text du } { \text dq } \cdot \dfrac { \text dq } { \text dt } = v \ , i $ electrical power is the product of voltage times current . in units of watts . summary these mental models for current and voltage will get us started on all sorts of interesting electric circuits . if you want to reach beyond this intuitive description of voltage you can read this more formal mathematical description of electric potential and voltage .
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if you hear , `` the current across ... '' , it should sound odd . voltage to get our initial toehold on the concept of voltage , let 's look at an analogy : voltage resembles gravity for a mass $ m $ , a change of height $ h $ corresponds to a change in potential energy , $ \delta u = mg\delta h $ . for a charged particle $ q $ , a voltage $ v $ corresponds to a change in potential energy , $ \delta u = qv $ .
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how does voltage affect the gravity of an object which have potential energy ?
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voltage and current are the cornerstone concepts in electricity . we will create our first mental models for these basic electrical quantities . we will also talk about power , which is what happens when voltage and current act together . charge the concept of electricity arises from an observation of nature . we observe a force between objects , that , like gravity , acts at a distance . the source of this force has been given the name charge . a very noticeable thing about electric force is that it is large , far greater than the force of gravity . unlike gravity , however , there are two types of electric charge . opposite types of charge attract , and like types of charge repel . gravity has only one type : it only attracts , never repels . conductors and insulators conductors are made of atoms whose outer , or valence , electrons have relatively weak bonds to their nuclei , as shown in this fanciful image of a copper atom . when a bunch of metal atoms are together , they gladly share their outer electrons with each other , creating a `` swarm '' of electrons not associated with a particular nucleus . a very small electric force can make the electron swarm move . copper , gold , silver , and aluminum are good conductors . so is saltwater . there are also poor conductors . tungsten—a metal used for light bulb filaments—and carbon—used in graphite form in pencils—are relatively poor conductors because their electrons are less prone to move . insulators are materials whose outer electrons are tightly bound to their nuclei . modest electric forces are not able to pull these electrons free . when an electric force is applied , the electron clouds around the atom stretch and deform in response to the force , but the electrons do not depart . glass , plastic , stone , and air are insulators . even for insulators , though , electric force can always be turned up high enough to rip electrons away—this is called breakdown . that 's what is happening to air molecules when you see a spark . semiconductor materials fall between insulators and conductors . they usually act like insulators , but we can make them act like conductors under certain circumstances . the most well-known semiconductor material is silicon ( atomic number $ 14 $ ) . our ability to finely control the insulating and conducting properties of silicon allows us to create modern marvels like computers and mobile phones . the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current . current is reported as the number of charges per unit time passing through a boundary . visualize placing a boundary all the way through a wire . station yourself near the boundary and count the number of charges passing by . report how much charge passed through the boundary in one second . we assign a positive sign to current corresponding to the direction a positive charge would be moving . since current is the amount of charge passing through a boundary in a fixed amount of time , it can be expressed mathematically using the following equation : $ i = \dfrac { dq } { dt } $ that 's current in a nutshell . a few remarks on current what carries current in metal ? since electrons are free to move about in metals , moving electrons are what makes up the current in metals . the positive nuclei in metal atoms are fixed in place and do not contribute to current . even though electrons have a negative charge and do almost all the work in most electric circuits , we still define a positive current as the direction a positive charge would move . this is a very old historical convention . can current be carried by positive charges ? yes . there are lots of examples . current is carried by both positive and negative charges in saltwater : if we put ordinary table salt in water , it becomes a good conductor . table salt is sodium chloride , nacl . the salt dissolves in water , into free-floating na $ ^+ $ and cl $ ^- $ ions . both ions respond to electric force and move through the saltwater solution , in opposite directions . in this case , the current is composed of moving atoms , both positive and negative ions , not just loose electrons . inside our bodies , electrical currents are moving ions , both positive and negative . the same definition of current works : count the number of charges passing by in a fixed amount of time . what causes current ? charged objects move in response to electric and magnetic forces . these forces come from electric and magnetic fields , which in turn come from the position and motion of other charges . what is the speed of current ? we do n't talk very often about the speed of current . answering the question , `` how fast is the current flowing ? '' requires understanding of a complex physical phenomenon and is not often relevant . current usually is n't about meters per second , it 's about charge per second . more often , we answer the question `` how much current is flowing ? '' all the time . how do we talk about current ? when discussing current , terms like through and in make a lot of sense . current flows through a resistor ; current flows in a wire . if you hear , `` the current across ... '' , it should sound odd . voltage to get our initial toehold on the concept of voltage , let 's look at an analogy : voltage resembles gravity for a mass $ m $ , a change of height $ h $ corresponds to a change in potential energy , $ \delta u = mg\delta h $ . for a charged particle $ q $ , a voltage $ v $ corresponds to a change in potential energy , $ \delta u = qv $ . voltage in an electric circuit is analogous to the product of $ g\cdot \delta h $ . where $ g $ is the acceleration due to gravity and $ \delta h $ is the change of height . a ball at the top of the hill rolls down . when it is halfway down , it has given up half of its potential energy . an electron at the top of a voltage `` hill '' travels `` downhill '' through wires and elements of a circuit . it gives up its potential energy , doing work along the way . when the electron is halfway down the hill , it has given up , or `` dropped '' , half of its potential energy . for both the ball and the electron , the trip down the hill happens spontaneously . the ball and electron move towards a lower energy state all by themselves . on the trip down , there can be things in the way of the ball , like trees or bears to bounce off . for electrons , we can guide electrons using wires and make them flow through electronic components —circuit design— and do interesting things along the way . we can express the voltage between two points mathematically as the change of energy experienced by a charge : $ v = \dfrac { \delta u } { q } $ that 's an intuitive description of voltage in a nutshell . power power is defined as the rate energy ( $ \text u $ ) is transformed or transferred over time . we measure power in units of joules/second , also known as watts . ( $ 1 \ , \text { watt } = 1\ , \text { joule } /\text { second } $ ) $ \text { power } = \dfrac { \text du } { \text dt } $ an electric circuit is capable of transferring power . current is the rate of flow of charge , and voltage measures the energy transferred per unit of charge . we can insert these definitions into the equation for power : $ \text { power } = \dfrac { \text du } { \text dt } = \dfrac { \text du } { \text dq } \cdot \dfrac { \text dq } { \text dt } = v \ , i $ electrical power is the product of voltage times current . in units of watts . summary these mental models for current and voltage will get us started on all sorts of interesting electric circuits . if you want to reach beyond this intuitive description of voltage you can read this more formal mathematical description of electric potential and voltage .
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what causes current ? charged objects move in response to electric and magnetic forces . these forces come from electric and magnetic fields , which in turn come from the position and motion of other charges .
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and how would you know the differences between different objects ?
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voltage and current are the cornerstone concepts in electricity . we will create our first mental models for these basic electrical quantities . we will also talk about power , which is what happens when voltage and current act together . charge the concept of electricity arises from an observation of nature . we observe a force between objects , that , like gravity , acts at a distance . the source of this force has been given the name charge . a very noticeable thing about electric force is that it is large , far greater than the force of gravity . unlike gravity , however , there are two types of electric charge . opposite types of charge attract , and like types of charge repel . gravity has only one type : it only attracts , never repels . conductors and insulators conductors are made of atoms whose outer , or valence , electrons have relatively weak bonds to their nuclei , as shown in this fanciful image of a copper atom . when a bunch of metal atoms are together , they gladly share their outer electrons with each other , creating a `` swarm '' of electrons not associated with a particular nucleus . a very small electric force can make the electron swarm move . copper , gold , silver , and aluminum are good conductors . so is saltwater . there are also poor conductors . tungsten—a metal used for light bulb filaments—and carbon—used in graphite form in pencils—are relatively poor conductors because their electrons are less prone to move . insulators are materials whose outer electrons are tightly bound to their nuclei . modest electric forces are not able to pull these electrons free . when an electric force is applied , the electron clouds around the atom stretch and deform in response to the force , but the electrons do not depart . glass , plastic , stone , and air are insulators . even for insulators , though , electric force can always be turned up high enough to rip electrons away—this is called breakdown . that 's what is happening to air molecules when you see a spark . semiconductor materials fall between insulators and conductors . they usually act like insulators , but we can make them act like conductors under certain circumstances . the most well-known semiconductor material is silicon ( atomic number $ 14 $ ) . our ability to finely control the insulating and conducting properties of silicon allows us to create modern marvels like computers and mobile phones . the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current . current is reported as the number of charges per unit time passing through a boundary . visualize placing a boundary all the way through a wire . station yourself near the boundary and count the number of charges passing by . report how much charge passed through the boundary in one second . we assign a positive sign to current corresponding to the direction a positive charge would be moving . since current is the amount of charge passing through a boundary in a fixed amount of time , it can be expressed mathematically using the following equation : $ i = \dfrac { dq } { dt } $ that 's current in a nutshell . a few remarks on current what carries current in metal ? since electrons are free to move about in metals , moving electrons are what makes up the current in metals . the positive nuclei in metal atoms are fixed in place and do not contribute to current . even though electrons have a negative charge and do almost all the work in most electric circuits , we still define a positive current as the direction a positive charge would move . this is a very old historical convention . can current be carried by positive charges ? yes . there are lots of examples . current is carried by both positive and negative charges in saltwater : if we put ordinary table salt in water , it becomes a good conductor . table salt is sodium chloride , nacl . the salt dissolves in water , into free-floating na $ ^+ $ and cl $ ^- $ ions . both ions respond to electric force and move through the saltwater solution , in opposite directions . in this case , the current is composed of moving atoms , both positive and negative ions , not just loose electrons . inside our bodies , electrical currents are moving ions , both positive and negative . the same definition of current works : count the number of charges passing by in a fixed amount of time . what causes current ? charged objects move in response to electric and magnetic forces . these forces come from electric and magnetic fields , which in turn come from the position and motion of other charges . what is the speed of current ? we do n't talk very often about the speed of current . answering the question , `` how fast is the current flowing ? '' requires understanding of a complex physical phenomenon and is not often relevant . current usually is n't about meters per second , it 's about charge per second . more often , we answer the question `` how much current is flowing ? '' all the time . how do we talk about current ? when discussing current , terms like through and in make a lot of sense . current flows through a resistor ; current flows in a wire . if you hear , `` the current across ... '' , it should sound odd . voltage to get our initial toehold on the concept of voltage , let 's look at an analogy : voltage resembles gravity for a mass $ m $ , a change of height $ h $ corresponds to a change in potential energy , $ \delta u = mg\delta h $ . for a charged particle $ q $ , a voltage $ v $ corresponds to a change in potential energy , $ \delta u = qv $ . voltage in an electric circuit is analogous to the product of $ g\cdot \delta h $ . where $ g $ is the acceleration due to gravity and $ \delta h $ is the change of height . a ball at the top of the hill rolls down . when it is halfway down , it has given up half of its potential energy . an electron at the top of a voltage `` hill '' travels `` downhill '' through wires and elements of a circuit . it gives up its potential energy , doing work along the way . when the electron is halfway down the hill , it has given up , or `` dropped '' , half of its potential energy . for both the ball and the electron , the trip down the hill happens spontaneously . the ball and electron move towards a lower energy state all by themselves . on the trip down , there can be things in the way of the ball , like trees or bears to bounce off . for electrons , we can guide electrons using wires and make them flow through electronic components —circuit design— and do interesting things along the way . we can express the voltage between two points mathematically as the change of energy experienced by a charge : $ v = \dfrac { \delta u } { q } $ that 's an intuitive description of voltage in a nutshell . power power is defined as the rate energy ( $ \text u $ ) is transformed or transferred over time . we measure power in units of joules/second , also known as watts . ( $ 1 \ , \text { watt } = 1\ , \text { joule } /\text { second } $ ) $ \text { power } = \dfrac { \text du } { \text dt } $ an electric circuit is capable of transferring power . current is the rate of flow of charge , and voltage measures the energy transferred per unit of charge . we can insert these definitions into the equation for power : $ \text { power } = \dfrac { \text du } { \text dt } = \dfrac { \text du } { \text dq } \cdot \dfrac { \text dq } { \text dt } = v \ , i $ electrical power is the product of voltage times current . in units of watts . summary these mental models for current and voltage will get us started on all sorts of interesting electric circuits . if you want to reach beyond this intuitive description of voltage you can read this more formal mathematical description of electric potential and voltage .
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it gives up its potential energy , doing work along the way . when the electron is halfway down the hill , it has given up , or `` dropped '' , half of its potential energy . for both the ball and the electron , the trip down the hill happens spontaneously .
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if there is nothing in the circuit ( shortcut ) , will the electron still lose half of its potential energy when halfway ?
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voltage and current are the cornerstone concepts in electricity . we will create our first mental models for these basic electrical quantities . we will also talk about power , which is what happens when voltage and current act together . charge the concept of electricity arises from an observation of nature . we observe a force between objects , that , like gravity , acts at a distance . the source of this force has been given the name charge . a very noticeable thing about electric force is that it is large , far greater than the force of gravity . unlike gravity , however , there are two types of electric charge . opposite types of charge attract , and like types of charge repel . gravity has only one type : it only attracts , never repels . conductors and insulators conductors are made of atoms whose outer , or valence , electrons have relatively weak bonds to their nuclei , as shown in this fanciful image of a copper atom . when a bunch of metal atoms are together , they gladly share their outer electrons with each other , creating a `` swarm '' of electrons not associated with a particular nucleus . a very small electric force can make the electron swarm move . copper , gold , silver , and aluminum are good conductors . so is saltwater . there are also poor conductors . tungsten—a metal used for light bulb filaments—and carbon—used in graphite form in pencils—are relatively poor conductors because their electrons are less prone to move . insulators are materials whose outer electrons are tightly bound to their nuclei . modest electric forces are not able to pull these electrons free . when an electric force is applied , the electron clouds around the atom stretch and deform in response to the force , but the electrons do not depart . glass , plastic , stone , and air are insulators . even for insulators , though , electric force can always be turned up high enough to rip electrons away—this is called breakdown . that 's what is happening to air molecules when you see a spark . semiconductor materials fall between insulators and conductors . they usually act like insulators , but we can make them act like conductors under certain circumstances . the most well-known semiconductor material is silicon ( atomic number $ 14 $ ) . our ability to finely control the insulating and conducting properties of silicon allows us to create modern marvels like computers and mobile phones . the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current . current is reported as the number of charges per unit time passing through a boundary . visualize placing a boundary all the way through a wire . station yourself near the boundary and count the number of charges passing by . report how much charge passed through the boundary in one second . we assign a positive sign to current corresponding to the direction a positive charge would be moving . since current is the amount of charge passing through a boundary in a fixed amount of time , it can be expressed mathematically using the following equation : $ i = \dfrac { dq } { dt } $ that 's current in a nutshell . a few remarks on current what carries current in metal ? since electrons are free to move about in metals , moving electrons are what makes up the current in metals . the positive nuclei in metal atoms are fixed in place and do not contribute to current . even though electrons have a negative charge and do almost all the work in most electric circuits , we still define a positive current as the direction a positive charge would move . this is a very old historical convention . can current be carried by positive charges ? yes . there are lots of examples . current is carried by both positive and negative charges in saltwater : if we put ordinary table salt in water , it becomes a good conductor . table salt is sodium chloride , nacl . the salt dissolves in water , into free-floating na $ ^+ $ and cl $ ^- $ ions . both ions respond to electric force and move through the saltwater solution , in opposite directions . in this case , the current is composed of moving atoms , both positive and negative ions , not just loose electrons . inside our bodies , electrical currents are moving ions , both positive and negative . the same definition of current works : count the number of charges passing by in a fixed amount of time . what causes current ? charged objects move in response to electric and magnetic forces . these forces come from electric and magnetic fields , which in turn come from the position and motion of other charges . what is the speed of current ? we do n't talk very often about the speed of current . answering the question , `` how fast is the current flowing ? '' requires understanding of a complex physical phenomenon and is not often relevant . current usually is n't about meters per second , it 's about charge per second . more often , we answer the question `` how much current is flowing ? '' all the time . how do we talk about current ? when discussing current , terms like through and in make a lot of sense . current flows through a resistor ; current flows in a wire . if you hear , `` the current across ... '' , it should sound odd . voltage to get our initial toehold on the concept of voltage , let 's look at an analogy : voltage resembles gravity for a mass $ m $ , a change of height $ h $ corresponds to a change in potential energy , $ \delta u = mg\delta h $ . for a charged particle $ q $ , a voltage $ v $ corresponds to a change in potential energy , $ \delta u = qv $ . voltage in an electric circuit is analogous to the product of $ g\cdot \delta h $ . where $ g $ is the acceleration due to gravity and $ \delta h $ is the change of height . a ball at the top of the hill rolls down . when it is halfway down , it has given up half of its potential energy . an electron at the top of a voltage `` hill '' travels `` downhill '' through wires and elements of a circuit . it gives up its potential energy , doing work along the way . when the electron is halfway down the hill , it has given up , or `` dropped '' , half of its potential energy . for both the ball and the electron , the trip down the hill happens spontaneously . the ball and electron move towards a lower energy state all by themselves . on the trip down , there can be things in the way of the ball , like trees or bears to bounce off . for electrons , we can guide electrons using wires and make them flow through electronic components —circuit design— and do interesting things along the way . we can express the voltage between two points mathematically as the change of energy experienced by a charge : $ v = \dfrac { \delta u } { q } $ that 's an intuitive description of voltage in a nutshell . power power is defined as the rate energy ( $ \text u $ ) is transformed or transferred over time . we measure power in units of joules/second , also known as watts . ( $ 1 \ , \text { watt } = 1\ , \text { joule } /\text { second } $ ) $ \text { power } = \dfrac { \text du } { \text dt } $ an electric circuit is capable of transferring power . current is the rate of flow of charge , and voltage measures the energy transferred per unit of charge . we can insert these definitions into the equation for power : $ \text { power } = \dfrac { \text du } { \text dt } = \dfrac { \text du } { \text dq } \cdot \dfrac { \text dq } { \text dt } = v \ , i $ electrical power is the product of voltage times current . in units of watts . summary these mental models for current and voltage will get us started on all sorts of interesting electric circuits . if you want to reach beyond this intuitive description of voltage you can read this more formal mathematical description of electric potential and voltage .
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both ions respond to electric force and move through the saltwater solution , in opposite directions . in this case , the current is composed of moving atoms , both positive and negative ions , not just loose electrons . inside our bodies , electrical currents are moving ions , both positive and negative .
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so , current does n't only consist of electrons , but also positive , and negative ions , right ?
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voltage and current are the cornerstone concepts in electricity . we will create our first mental models for these basic electrical quantities . we will also talk about power , which is what happens when voltage and current act together . charge the concept of electricity arises from an observation of nature . we observe a force between objects , that , like gravity , acts at a distance . the source of this force has been given the name charge . a very noticeable thing about electric force is that it is large , far greater than the force of gravity . unlike gravity , however , there are two types of electric charge . opposite types of charge attract , and like types of charge repel . gravity has only one type : it only attracts , never repels . conductors and insulators conductors are made of atoms whose outer , or valence , electrons have relatively weak bonds to their nuclei , as shown in this fanciful image of a copper atom . when a bunch of metal atoms are together , they gladly share their outer electrons with each other , creating a `` swarm '' of electrons not associated with a particular nucleus . a very small electric force can make the electron swarm move . copper , gold , silver , and aluminum are good conductors . so is saltwater . there are also poor conductors . tungsten—a metal used for light bulb filaments—and carbon—used in graphite form in pencils—are relatively poor conductors because their electrons are less prone to move . insulators are materials whose outer electrons are tightly bound to their nuclei . modest electric forces are not able to pull these electrons free . when an electric force is applied , the electron clouds around the atom stretch and deform in response to the force , but the electrons do not depart . glass , plastic , stone , and air are insulators . even for insulators , though , electric force can always be turned up high enough to rip electrons away—this is called breakdown . that 's what is happening to air molecules when you see a spark . semiconductor materials fall between insulators and conductors . they usually act like insulators , but we can make them act like conductors under certain circumstances . the most well-known semiconductor material is silicon ( atomic number $ 14 $ ) . our ability to finely control the insulating and conducting properties of silicon allows us to create modern marvels like computers and mobile phones . the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current . current is reported as the number of charges per unit time passing through a boundary . visualize placing a boundary all the way through a wire . station yourself near the boundary and count the number of charges passing by . report how much charge passed through the boundary in one second . we assign a positive sign to current corresponding to the direction a positive charge would be moving . since current is the amount of charge passing through a boundary in a fixed amount of time , it can be expressed mathematically using the following equation : $ i = \dfrac { dq } { dt } $ that 's current in a nutshell . a few remarks on current what carries current in metal ? since electrons are free to move about in metals , moving electrons are what makes up the current in metals . the positive nuclei in metal atoms are fixed in place and do not contribute to current . even though electrons have a negative charge and do almost all the work in most electric circuits , we still define a positive current as the direction a positive charge would move . this is a very old historical convention . can current be carried by positive charges ? yes . there are lots of examples . current is carried by both positive and negative charges in saltwater : if we put ordinary table salt in water , it becomes a good conductor . table salt is sodium chloride , nacl . the salt dissolves in water , into free-floating na $ ^+ $ and cl $ ^- $ ions . both ions respond to electric force and move through the saltwater solution , in opposite directions . in this case , the current is composed of moving atoms , both positive and negative ions , not just loose electrons . inside our bodies , electrical currents are moving ions , both positive and negative . the same definition of current works : count the number of charges passing by in a fixed amount of time . what causes current ? charged objects move in response to electric and magnetic forces . these forces come from electric and magnetic fields , which in turn come from the position and motion of other charges . what is the speed of current ? we do n't talk very often about the speed of current . answering the question , `` how fast is the current flowing ? '' requires understanding of a complex physical phenomenon and is not often relevant . current usually is n't about meters per second , it 's about charge per second . more often , we answer the question `` how much current is flowing ? '' all the time . how do we talk about current ? when discussing current , terms like through and in make a lot of sense . current flows through a resistor ; current flows in a wire . if you hear , `` the current across ... '' , it should sound odd . voltage to get our initial toehold on the concept of voltage , let 's look at an analogy : voltage resembles gravity for a mass $ m $ , a change of height $ h $ corresponds to a change in potential energy , $ \delta u = mg\delta h $ . for a charged particle $ q $ , a voltage $ v $ corresponds to a change in potential energy , $ \delta u = qv $ . voltage in an electric circuit is analogous to the product of $ g\cdot \delta h $ . where $ g $ is the acceleration due to gravity and $ \delta h $ is the change of height . a ball at the top of the hill rolls down . when it is halfway down , it has given up half of its potential energy . an electron at the top of a voltage `` hill '' travels `` downhill '' through wires and elements of a circuit . it gives up its potential energy , doing work along the way . when the electron is halfway down the hill , it has given up , or `` dropped '' , half of its potential energy . for both the ball and the electron , the trip down the hill happens spontaneously . the ball and electron move towards a lower energy state all by themselves . on the trip down , there can be things in the way of the ball , like trees or bears to bounce off . for electrons , we can guide electrons using wires and make them flow through electronic components —circuit design— and do interesting things along the way . we can express the voltage between two points mathematically as the change of energy experienced by a charge : $ v = \dfrac { \delta u } { q } $ that 's an intuitive description of voltage in a nutshell . power power is defined as the rate energy ( $ \text u $ ) is transformed or transferred over time . we measure power in units of joules/second , also known as watts . ( $ 1 \ , \text { watt } = 1\ , \text { joule } /\text { second } $ ) $ \text { power } = \dfrac { \text du } { \text dt } $ an electric circuit is capable of transferring power . current is the rate of flow of charge , and voltage measures the energy transferred per unit of charge . we can insert these definitions into the equation for power : $ \text { power } = \dfrac { \text du } { \text dt } = \dfrac { \text du } { \text dq } \cdot \dfrac { \text dq } { \text dt } = v \ , i $ electrical power is the product of voltage times current . in units of watts . summary these mental models for current and voltage will get us started on all sorts of interesting electric circuits . if you want to reach beyond this intuitive description of voltage you can read this more formal mathematical description of electric potential and voltage .
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voltage and current are the cornerstone concepts in electricity . we will create our first mental models for these basic electrical quantities .
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what does d mean in the formulas ?
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voltage and current are the cornerstone concepts in electricity . we will create our first mental models for these basic electrical quantities . we will also talk about power , which is what happens when voltage and current act together . charge the concept of electricity arises from an observation of nature . we observe a force between objects , that , like gravity , acts at a distance . the source of this force has been given the name charge . a very noticeable thing about electric force is that it is large , far greater than the force of gravity . unlike gravity , however , there are two types of electric charge . opposite types of charge attract , and like types of charge repel . gravity has only one type : it only attracts , never repels . conductors and insulators conductors are made of atoms whose outer , or valence , electrons have relatively weak bonds to their nuclei , as shown in this fanciful image of a copper atom . when a bunch of metal atoms are together , they gladly share their outer electrons with each other , creating a `` swarm '' of electrons not associated with a particular nucleus . a very small electric force can make the electron swarm move . copper , gold , silver , and aluminum are good conductors . so is saltwater . there are also poor conductors . tungsten—a metal used for light bulb filaments—and carbon—used in graphite form in pencils—are relatively poor conductors because their electrons are less prone to move . insulators are materials whose outer electrons are tightly bound to their nuclei . modest electric forces are not able to pull these electrons free . when an electric force is applied , the electron clouds around the atom stretch and deform in response to the force , but the electrons do not depart . glass , plastic , stone , and air are insulators . even for insulators , though , electric force can always be turned up high enough to rip electrons away—this is called breakdown . that 's what is happening to air molecules when you see a spark . semiconductor materials fall between insulators and conductors . they usually act like insulators , but we can make them act like conductors under certain circumstances . the most well-known semiconductor material is silicon ( atomic number $ 14 $ ) . our ability to finely control the insulating and conducting properties of silicon allows us to create modern marvels like computers and mobile phones . the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current . current is reported as the number of charges per unit time passing through a boundary . visualize placing a boundary all the way through a wire . station yourself near the boundary and count the number of charges passing by . report how much charge passed through the boundary in one second . we assign a positive sign to current corresponding to the direction a positive charge would be moving . since current is the amount of charge passing through a boundary in a fixed amount of time , it can be expressed mathematically using the following equation : $ i = \dfrac { dq } { dt } $ that 's current in a nutshell . a few remarks on current what carries current in metal ? since electrons are free to move about in metals , moving electrons are what makes up the current in metals . the positive nuclei in metal atoms are fixed in place and do not contribute to current . even though electrons have a negative charge and do almost all the work in most electric circuits , we still define a positive current as the direction a positive charge would move . this is a very old historical convention . can current be carried by positive charges ? yes . there are lots of examples . current is carried by both positive and negative charges in saltwater : if we put ordinary table salt in water , it becomes a good conductor . table salt is sodium chloride , nacl . the salt dissolves in water , into free-floating na $ ^+ $ and cl $ ^- $ ions . both ions respond to electric force and move through the saltwater solution , in opposite directions . in this case , the current is composed of moving atoms , both positive and negative ions , not just loose electrons . inside our bodies , electrical currents are moving ions , both positive and negative . the same definition of current works : count the number of charges passing by in a fixed amount of time . what causes current ? charged objects move in response to electric and magnetic forces . these forces come from electric and magnetic fields , which in turn come from the position and motion of other charges . what is the speed of current ? we do n't talk very often about the speed of current . answering the question , `` how fast is the current flowing ? '' requires understanding of a complex physical phenomenon and is not often relevant . current usually is n't about meters per second , it 's about charge per second . more often , we answer the question `` how much current is flowing ? '' all the time . how do we talk about current ? when discussing current , terms like through and in make a lot of sense . current flows through a resistor ; current flows in a wire . if you hear , `` the current across ... '' , it should sound odd . voltage to get our initial toehold on the concept of voltage , let 's look at an analogy : voltage resembles gravity for a mass $ m $ , a change of height $ h $ corresponds to a change in potential energy , $ \delta u = mg\delta h $ . for a charged particle $ q $ , a voltage $ v $ corresponds to a change in potential energy , $ \delta u = qv $ . voltage in an electric circuit is analogous to the product of $ g\cdot \delta h $ . where $ g $ is the acceleration due to gravity and $ \delta h $ is the change of height . a ball at the top of the hill rolls down . when it is halfway down , it has given up half of its potential energy . an electron at the top of a voltage `` hill '' travels `` downhill '' through wires and elements of a circuit . it gives up its potential energy , doing work along the way . when the electron is halfway down the hill , it has given up , or `` dropped '' , half of its potential energy . for both the ball and the electron , the trip down the hill happens spontaneously . the ball and electron move towards a lower energy state all by themselves . on the trip down , there can be things in the way of the ball , like trees or bears to bounce off . for electrons , we can guide electrons using wires and make them flow through electronic components —circuit design— and do interesting things along the way . we can express the voltage between two points mathematically as the change of energy experienced by a charge : $ v = \dfrac { \delta u } { q } $ that 's an intuitive description of voltage in a nutshell . power power is defined as the rate energy ( $ \text u $ ) is transformed or transferred over time . we measure power in units of joules/second , also known as watts . ( $ 1 \ , \text { watt } = 1\ , \text { joule } /\text { second } $ ) $ \text { power } = \dfrac { \text du } { \text dt } $ an electric circuit is capable of transferring power . current is the rate of flow of charge , and voltage measures the energy transferred per unit of charge . we can insert these definitions into the equation for power : $ \text { power } = \dfrac { \text du } { \text dt } = \dfrac { \text du } { \text dq } \cdot \dfrac { \text dq } { \text dt } = v \ , i $ electrical power is the product of voltage times current . in units of watts . summary these mental models for current and voltage will get us started on all sorts of interesting electric circuits . if you want to reach beyond this intuitive description of voltage you can read this more formal mathematical description of electric potential and voltage .
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so is saltwater . there are also poor conductors . tungsten—a metal used for light bulb filaments—and carbon—used in graphite form in pencils—are relatively poor conductors because their electrons are less prone to move .
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why graphite is a poor conductor ?
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voltage and current are the cornerstone concepts in electricity . we will create our first mental models for these basic electrical quantities . we will also talk about power , which is what happens when voltage and current act together . charge the concept of electricity arises from an observation of nature . we observe a force between objects , that , like gravity , acts at a distance . the source of this force has been given the name charge . a very noticeable thing about electric force is that it is large , far greater than the force of gravity . unlike gravity , however , there are two types of electric charge . opposite types of charge attract , and like types of charge repel . gravity has only one type : it only attracts , never repels . conductors and insulators conductors are made of atoms whose outer , or valence , electrons have relatively weak bonds to their nuclei , as shown in this fanciful image of a copper atom . when a bunch of metal atoms are together , they gladly share their outer electrons with each other , creating a `` swarm '' of electrons not associated with a particular nucleus . a very small electric force can make the electron swarm move . copper , gold , silver , and aluminum are good conductors . so is saltwater . there are also poor conductors . tungsten—a metal used for light bulb filaments—and carbon—used in graphite form in pencils—are relatively poor conductors because their electrons are less prone to move . insulators are materials whose outer electrons are tightly bound to their nuclei . modest electric forces are not able to pull these electrons free . when an electric force is applied , the electron clouds around the atom stretch and deform in response to the force , but the electrons do not depart . glass , plastic , stone , and air are insulators . even for insulators , though , electric force can always be turned up high enough to rip electrons away—this is called breakdown . that 's what is happening to air molecules when you see a spark . semiconductor materials fall between insulators and conductors . they usually act like insulators , but we can make them act like conductors under certain circumstances . the most well-known semiconductor material is silicon ( atomic number $ 14 $ ) . our ability to finely control the insulating and conducting properties of silicon allows us to create modern marvels like computers and mobile phones . the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current . current is reported as the number of charges per unit time passing through a boundary . visualize placing a boundary all the way through a wire . station yourself near the boundary and count the number of charges passing by . report how much charge passed through the boundary in one second . we assign a positive sign to current corresponding to the direction a positive charge would be moving . since current is the amount of charge passing through a boundary in a fixed amount of time , it can be expressed mathematically using the following equation : $ i = \dfrac { dq } { dt } $ that 's current in a nutshell . a few remarks on current what carries current in metal ? since electrons are free to move about in metals , moving electrons are what makes up the current in metals . the positive nuclei in metal atoms are fixed in place and do not contribute to current . even though electrons have a negative charge and do almost all the work in most electric circuits , we still define a positive current as the direction a positive charge would move . this is a very old historical convention . can current be carried by positive charges ? yes . there are lots of examples . current is carried by both positive and negative charges in saltwater : if we put ordinary table salt in water , it becomes a good conductor . table salt is sodium chloride , nacl . the salt dissolves in water , into free-floating na $ ^+ $ and cl $ ^- $ ions . both ions respond to electric force and move through the saltwater solution , in opposite directions . in this case , the current is composed of moving atoms , both positive and negative ions , not just loose electrons . inside our bodies , electrical currents are moving ions , both positive and negative . the same definition of current works : count the number of charges passing by in a fixed amount of time . what causes current ? charged objects move in response to electric and magnetic forces . these forces come from electric and magnetic fields , which in turn come from the position and motion of other charges . what is the speed of current ? we do n't talk very often about the speed of current . answering the question , `` how fast is the current flowing ? '' requires understanding of a complex physical phenomenon and is not often relevant . current usually is n't about meters per second , it 's about charge per second . more often , we answer the question `` how much current is flowing ? '' all the time . how do we talk about current ? when discussing current , terms like through and in make a lot of sense . current flows through a resistor ; current flows in a wire . if you hear , `` the current across ... '' , it should sound odd . voltage to get our initial toehold on the concept of voltage , let 's look at an analogy : voltage resembles gravity for a mass $ m $ , a change of height $ h $ corresponds to a change in potential energy , $ \delta u = mg\delta h $ . for a charged particle $ q $ , a voltage $ v $ corresponds to a change in potential energy , $ \delta u = qv $ . voltage in an electric circuit is analogous to the product of $ g\cdot \delta h $ . where $ g $ is the acceleration due to gravity and $ \delta h $ is the change of height . a ball at the top of the hill rolls down . when it is halfway down , it has given up half of its potential energy . an electron at the top of a voltage `` hill '' travels `` downhill '' through wires and elements of a circuit . it gives up its potential energy , doing work along the way . when the electron is halfway down the hill , it has given up , or `` dropped '' , half of its potential energy . for both the ball and the electron , the trip down the hill happens spontaneously . the ball and electron move towards a lower energy state all by themselves . on the trip down , there can be things in the way of the ball , like trees or bears to bounce off . for electrons , we can guide electrons using wires and make them flow through electronic components —circuit design— and do interesting things along the way . we can express the voltage between two points mathematically as the change of energy experienced by a charge : $ v = \dfrac { \delta u } { q } $ that 's an intuitive description of voltage in a nutshell . power power is defined as the rate energy ( $ \text u $ ) is transformed or transferred over time . we measure power in units of joules/second , also known as watts . ( $ 1 \ , \text { watt } = 1\ , \text { joule } /\text { second } $ ) $ \text { power } = \dfrac { \text du } { \text dt } $ an electric circuit is capable of transferring power . current is the rate of flow of charge , and voltage measures the energy transferred per unit of charge . we can insert these definitions into the equation for power : $ \text { power } = \dfrac { \text du } { \text dt } = \dfrac { \text du } { \text dq } \cdot \dfrac { \text dq } { \text dt } = v \ , i $ electrical power is the product of voltage times current . in units of watts . summary these mental models for current and voltage will get us started on all sorts of interesting electric circuits . if you want to reach beyond this intuitive description of voltage you can read this more formal mathematical description of electric potential and voltage .
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voltage and current are the cornerstone concepts in electricity . we will create our first mental models for these basic electrical quantities .
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what does the d mean ?
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voltage and current are the cornerstone concepts in electricity . we will create our first mental models for these basic electrical quantities . we will also talk about power , which is what happens when voltage and current act together . charge the concept of electricity arises from an observation of nature . we observe a force between objects , that , like gravity , acts at a distance . the source of this force has been given the name charge . a very noticeable thing about electric force is that it is large , far greater than the force of gravity . unlike gravity , however , there are two types of electric charge . opposite types of charge attract , and like types of charge repel . gravity has only one type : it only attracts , never repels . conductors and insulators conductors are made of atoms whose outer , or valence , electrons have relatively weak bonds to their nuclei , as shown in this fanciful image of a copper atom . when a bunch of metal atoms are together , they gladly share their outer electrons with each other , creating a `` swarm '' of electrons not associated with a particular nucleus . a very small electric force can make the electron swarm move . copper , gold , silver , and aluminum are good conductors . so is saltwater . there are also poor conductors . tungsten—a metal used for light bulb filaments—and carbon—used in graphite form in pencils—are relatively poor conductors because their electrons are less prone to move . insulators are materials whose outer electrons are tightly bound to their nuclei . modest electric forces are not able to pull these electrons free . when an electric force is applied , the electron clouds around the atom stretch and deform in response to the force , but the electrons do not depart . glass , plastic , stone , and air are insulators . even for insulators , though , electric force can always be turned up high enough to rip electrons away—this is called breakdown . that 's what is happening to air molecules when you see a spark . semiconductor materials fall between insulators and conductors . they usually act like insulators , but we can make them act like conductors under certain circumstances . the most well-known semiconductor material is silicon ( atomic number $ 14 $ ) . our ability to finely control the insulating and conducting properties of silicon allows us to create modern marvels like computers and mobile phones . the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current . current is reported as the number of charges per unit time passing through a boundary . visualize placing a boundary all the way through a wire . station yourself near the boundary and count the number of charges passing by . report how much charge passed through the boundary in one second . we assign a positive sign to current corresponding to the direction a positive charge would be moving . since current is the amount of charge passing through a boundary in a fixed amount of time , it can be expressed mathematically using the following equation : $ i = \dfrac { dq } { dt } $ that 's current in a nutshell . a few remarks on current what carries current in metal ? since electrons are free to move about in metals , moving electrons are what makes up the current in metals . the positive nuclei in metal atoms are fixed in place and do not contribute to current . even though electrons have a negative charge and do almost all the work in most electric circuits , we still define a positive current as the direction a positive charge would move . this is a very old historical convention . can current be carried by positive charges ? yes . there are lots of examples . current is carried by both positive and negative charges in saltwater : if we put ordinary table salt in water , it becomes a good conductor . table salt is sodium chloride , nacl . the salt dissolves in water , into free-floating na $ ^+ $ and cl $ ^- $ ions . both ions respond to electric force and move through the saltwater solution , in opposite directions . in this case , the current is composed of moving atoms , both positive and negative ions , not just loose electrons . inside our bodies , electrical currents are moving ions , both positive and negative . the same definition of current works : count the number of charges passing by in a fixed amount of time . what causes current ? charged objects move in response to electric and magnetic forces . these forces come from electric and magnetic fields , which in turn come from the position and motion of other charges . what is the speed of current ? we do n't talk very often about the speed of current . answering the question , `` how fast is the current flowing ? '' requires understanding of a complex physical phenomenon and is not often relevant . current usually is n't about meters per second , it 's about charge per second . more often , we answer the question `` how much current is flowing ? '' all the time . how do we talk about current ? when discussing current , terms like through and in make a lot of sense . current flows through a resistor ; current flows in a wire . if you hear , `` the current across ... '' , it should sound odd . voltage to get our initial toehold on the concept of voltage , let 's look at an analogy : voltage resembles gravity for a mass $ m $ , a change of height $ h $ corresponds to a change in potential energy , $ \delta u = mg\delta h $ . for a charged particle $ q $ , a voltage $ v $ corresponds to a change in potential energy , $ \delta u = qv $ . voltage in an electric circuit is analogous to the product of $ g\cdot \delta h $ . where $ g $ is the acceleration due to gravity and $ \delta h $ is the change of height . a ball at the top of the hill rolls down . when it is halfway down , it has given up half of its potential energy . an electron at the top of a voltage `` hill '' travels `` downhill '' through wires and elements of a circuit . it gives up its potential energy , doing work along the way . when the electron is halfway down the hill , it has given up , or `` dropped '' , half of its potential energy . for both the ball and the electron , the trip down the hill happens spontaneously . the ball and electron move towards a lower energy state all by themselves . on the trip down , there can be things in the way of the ball , like trees or bears to bounce off . for electrons , we can guide electrons using wires and make them flow through electronic components —circuit design— and do interesting things along the way . we can express the voltage between two points mathematically as the change of energy experienced by a charge : $ v = \dfrac { \delta u } { q } $ that 's an intuitive description of voltage in a nutshell . power power is defined as the rate energy ( $ \text u $ ) is transformed or transferred over time . we measure power in units of joules/second , also known as watts . ( $ 1 \ , \text { watt } = 1\ , \text { joule } /\text { second } $ ) $ \text { power } = \dfrac { \text du } { \text dt } $ an electric circuit is capable of transferring power . current is the rate of flow of charge , and voltage measures the energy transferred per unit of charge . we can insert these definitions into the equation for power : $ \text { power } = \dfrac { \text du } { \text dt } = \dfrac { \text du } { \text dq } \cdot \dfrac { \text dq } { \text dt } = v \ , i $ electrical power is the product of voltage times current . in units of watts . summary these mental models for current and voltage will get us started on all sorts of interesting electric circuits . if you want to reach beyond this intuitive description of voltage you can read this more formal mathematical description of electric potential and voltage .
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when an electric force is applied , the electron clouds around the atom stretch and deform in response to the force , but the electrons do not depart . glass , plastic , stone , and air are insulators . even for insulators , though , electric force can always be turned up high enough to rip electrons away—this is called breakdown .
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do insulators attract to magnets ?
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voltage and current are the cornerstone concepts in electricity . we will create our first mental models for these basic electrical quantities . we will also talk about power , which is what happens when voltage and current act together . charge the concept of electricity arises from an observation of nature . we observe a force between objects , that , like gravity , acts at a distance . the source of this force has been given the name charge . a very noticeable thing about electric force is that it is large , far greater than the force of gravity . unlike gravity , however , there are two types of electric charge . opposite types of charge attract , and like types of charge repel . gravity has only one type : it only attracts , never repels . conductors and insulators conductors are made of atoms whose outer , or valence , electrons have relatively weak bonds to their nuclei , as shown in this fanciful image of a copper atom . when a bunch of metal atoms are together , they gladly share their outer electrons with each other , creating a `` swarm '' of electrons not associated with a particular nucleus . a very small electric force can make the electron swarm move . copper , gold , silver , and aluminum are good conductors . so is saltwater . there are also poor conductors . tungsten—a metal used for light bulb filaments—and carbon—used in graphite form in pencils—are relatively poor conductors because their electrons are less prone to move . insulators are materials whose outer electrons are tightly bound to their nuclei . modest electric forces are not able to pull these electrons free . when an electric force is applied , the electron clouds around the atom stretch and deform in response to the force , but the electrons do not depart . glass , plastic , stone , and air are insulators . even for insulators , though , electric force can always be turned up high enough to rip electrons away—this is called breakdown . that 's what is happening to air molecules when you see a spark . semiconductor materials fall between insulators and conductors . they usually act like insulators , but we can make them act like conductors under certain circumstances . the most well-known semiconductor material is silicon ( atomic number $ 14 $ ) . our ability to finely control the insulating and conducting properties of silicon allows us to create modern marvels like computers and mobile phones . the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current . current is reported as the number of charges per unit time passing through a boundary . visualize placing a boundary all the way through a wire . station yourself near the boundary and count the number of charges passing by . report how much charge passed through the boundary in one second . we assign a positive sign to current corresponding to the direction a positive charge would be moving . since current is the amount of charge passing through a boundary in a fixed amount of time , it can be expressed mathematically using the following equation : $ i = \dfrac { dq } { dt } $ that 's current in a nutshell . a few remarks on current what carries current in metal ? since electrons are free to move about in metals , moving electrons are what makes up the current in metals . the positive nuclei in metal atoms are fixed in place and do not contribute to current . even though electrons have a negative charge and do almost all the work in most electric circuits , we still define a positive current as the direction a positive charge would move . this is a very old historical convention . can current be carried by positive charges ? yes . there are lots of examples . current is carried by both positive and negative charges in saltwater : if we put ordinary table salt in water , it becomes a good conductor . table salt is sodium chloride , nacl . the salt dissolves in water , into free-floating na $ ^+ $ and cl $ ^- $ ions . both ions respond to electric force and move through the saltwater solution , in opposite directions . in this case , the current is composed of moving atoms , both positive and negative ions , not just loose electrons . inside our bodies , electrical currents are moving ions , both positive and negative . the same definition of current works : count the number of charges passing by in a fixed amount of time . what causes current ? charged objects move in response to electric and magnetic forces . these forces come from electric and magnetic fields , which in turn come from the position and motion of other charges . what is the speed of current ? we do n't talk very often about the speed of current . answering the question , `` how fast is the current flowing ? '' requires understanding of a complex physical phenomenon and is not often relevant . current usually is n't about meters per second , it 's about charge per second . more often , we answer the question `` how much current is flowing ? '' all the time . how do we talk about current ? when discussing current , terms like through and in make a lot of sense . current flows through a resistor ; current flows in a wire . if you hear , `` the current across ... '' , it should sound odd . voltage to get our initial toehold on the concept of voltage , let 's look at an analogy : voltage resembles gravity for a mass $ m $ , a change of height $ h $ corresponds to a change in potential energy , $ \delta u = mg\delta h $ . for a charged particle $ q $ , a voltage $ v $ corresponds to a change in potential energy , $ \delta u = qv $ . voltage in an electric circuit is analogous to the product of $ g\cdot \delta h $ . where $ g $ is the acceleration due to gravity and $ \delta h $ is the change of height . a ball at the top of the hill rolls down . when it is halfway down , it has given up half of its potential energy . an electron at the top of a voltage `` hill '' travels `` downhill '' through wires and elements of a circuit . it gives up its potential energy , doing work along the way . when the electron is halfway down the hill , it has given up , or `` dropped '' , half of its potential energy . for both the ball and the electron , the trip down the hill happens spontaneously . the ball and electron move towards a lower energy state all by themselves . on the trip down , there can be things in the way of the ball , like trees or bears to bounce off . for electrons , we can guide electrons using wires and make them flow through electronic components —circuit design— and do interesting things along the way . we can express the voltage between two points mathematically as the change of energy experienced by a charge : $ v = \dfrac { \delta u } { q } $ that 's an intuitive description of voltage in a nutshell . power power is defined as the rate energy ( $ \text u $ ) is transformed or transferred over time . we measure power in units of joules/second , also known as watts . ( $ 1 \ , \text { watt } = 1\ , \text { joule } /\text { second } $ ) $ \text { power } = \dfrac { \text du } { \text dt } $ an electric circuit is capable of transferring power . current is the rate of flow of charge , and voltage measures the energy transferred per unit of charge . we can insert these definitions into the equation for power : $ \text { power } = \dfrac { \text du } { \text dt } = \dfrac { \text du } { \text dq } \cdot \dfrac { \text dq } { \text dt } = v \ , i $ electrical power is the product of voltage times current . in units of watts . summary these mental models for current and voltage will get us started on all sorts of interesting electric circuits . if you want to reach beyond this intuitive description of voltage you can read this more formal mathematical description of electric potential and voltage .
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modest electric forces are not able to pull these electrons free . when an electric force is applied , the electron clouds around the atom stretch and deform in response to the force , but the electrons do not depart . glass , plastic , stone , and air are insulators .
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this is just a more general question , but when electrons jump from atom to atom as described in the second section , what happens to the atom that loses an electron ?
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voltage and current are the cornerstone concepts in electricity . we will create our first mental models for these basic electrical quantities . we will also talk about power , which is what happens when voltage and current act together . charge the concept of electricity arises from an observation of nature . we observe a force between objects , that , like gravity , acts at a distance . the source of this force has been given the name charge . a very noticeable thing about electric force is that it is large , far greater than the force of gravity . unlike gravity , however , there are two types of electric charge . opposite types of charge attract , and like types of charge repel . gravity has only one type : it only attracts , never repels . conductors and insulators conductors are made of atoms whose outer , or valence , electrons have relatively weak bonds to their nuclei , as shown in this fanciful image of a copper atom . when a bunch of metal atoms are together , they gladly share their outer electrons with each other , creating a `` swarm '' of electrons not associated with a particular nucleus . a very small electric force can make the electron swarm move . copper , gold , silver , and aluminum are good conductors . so is saltwater . there are also poor conductors . tungsten—a metal used for light bulb filaments—and carbon—used in graphite form in pencils—are relatively poor conductors because their electrons are less prone to move . insulators are materials whose outer electrons are tightly bound to their nuclei . modest electric forces are not able to pull these electrons free . when an electric force is applied , the electron clouds around the atom stretch and deform in response to the force , but the electrons do not depart . glass , plastic , stone , and air are insulators . even for insulators , though , electric force can always be turned up high enough to rip electrons away—this is called breakdown . that 's what is happening to air molecules when you see a spark . semiconductor materials fall between insulators and conductors . they usually act like insulators , but we can make them act like conductors under certain circumstances . the most well-known semiconductor material is silicon ( atomic number $ 14 $ ) . our ability to finely control the insulating and conducting properties of silicon allows us to create modern marvels like computers and mobile phones . the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current . current is reported as the number of charges per unit time passing through a boundary . visualize placing a boundary all the way through a wire . station yourself near the boundary and count the number of charges passing by . report how much charge passed through the boundary in one second . we assign a positive sign to current corresponding to the direction a positive charge would be moving . since current is the amount of charge passing through a boundary in a fixed amount of time , it can be expressed mathematically using the following equation : $ i = \dfrac { dq } { dt } $ that 's current in a nutshell . a few remarks on current what carries current in metal ? since electrons are free to move about in metals , moving electrons are what makes up the current in metals . the positive nuclei in metal atoms are fixed in place and do not contribute to current . even though electrons have a negative charge and do almost all the work in most electric circuits , we still define a positive current as the direction a positive charge would move . this is a very old historical convention . can current be carried by positive charges ? yes . there are lots of examples . current is carried by both positive and negative charges in saltwater : if we put ordinary table salt in water , it becomes a good conductor . table salt is sodium chloride , nacl . the salt dissolves in water , into free-floating na $ ^+ $ and cl $ ^- $ ions . both ions respond to electric force and move through the saltwater solution , in opposite directions . in this case , the current is composed of moving atoms , both positive and negative ions , not just loose electrons . inside our bodies , electrical currents are moving ions , both positive and negative . the same definition of current works : count the number of charges passing by in a fixed amount of time . what causes current ? charged objects move in response to electric and magnetic forces . these forces come from electric and magnetic fields , which in turn come from the position and motion of other charges . what is the speed of current ? we do n't talk very often about the speed of current . answering the question , `` how fast is the current flowing ? '' requires understanding of a complex physical phenomenon and is not often relevant . current usually is n't about meters per second , it 's about charge per second . more often , we answer the question `` how much current is flowing ? '' all the time . how do we talk about current ? when discussing current , terms like through and in make a lot of sense . current flows through a resistor ; current flows in a wire . if you hear , `` the current across ... '' , it should sound odd . voltage to get our initial toehold on the concept of voltage , let 's look at an analogy : voltage resembles gravity for a mass $ m $ , a change of height $ h $ corresponds to a change in potential energy , $ \delta u = mg\delta h $ . for a charged particle $ q $ , a voltage $ v $ corresponds to a change in potential energy , $ \delta u = qv $ . voltage in an electric circuit is analogous to the product of $ g\cdot \delta h $ . where $ g $ is the acceleration due to gravity and $ \delta h $ is the change of height . a ball at the top of the hill rolls down . when it is halfway down , it has given up half of its potential energy . an electron at the top of a voltage `` hill '' travels `` downhill '' through wires and elements of a circuit . it gives up its potential energy , doing work along the way . when the electron is halfway down the hill , it has given up , or `` dropped '' , half of its potential energy . for both the ball and the electron , the trip down the hill happens spontaneously . the ball and electron move towards a lower energy state all by themselves . on the trip down , there can be things in the way of the ball , like trees or bears to bounce off . for electrons , we can guide electrons using wires and make them flow through electronic components —circuit design— and do interesting things along the way . we can express the voltage between two points mathematically as the change of energy experienced by a charge : $ v = \dfrac { \delta u } { q } $ that 's an intuitive description of voltage in a nutshell . power power is defined as the rate energy ( $ \text u $ ) is transformed or transferred over time . we measure power in units of joules/second , also known as watts . ( $ 1 \ , \text { watt } = 1\ , \text { joule } /\text { second } $ ) $ \text { power } = \dfrac { \text du } { \text dt } $ an electric circuit is capable of transferring power . current is the rate of flow of charge , and voltage measures the energy transferred per unit of charge . we can insert these definitions into the equation for power : $ \text { power } = \dfrac { \text du } { \text dt } = \dfrac { \text du } { \text dq } \cdot \dfrac { \text dq } { \text dt } = v \ , i $ electrical power is the product of voltage times current . in units of watts . summary these mental models for current and voltage will get us started on all sorts of interesting electric circuits . if you want to reach beyond this intuitive description of voltage you can read this more formal mathematical description of electric potential and voltage .
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voltage and current are the cornerstone concepts in electricity . we will create our first mental models for these basic electrical quantities .
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what do your variables in the equations represent ?
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voltage and current are the cornerstone concepts in electricity . we will create our first mental models for these basic electrical quantities . we will also talk about power , which is what happens when voltage and current act together . charge the concept of electricity arises from an observation of nature . we observe a force between objects , that , like gravity , acts at a distance . the source of this force has been given the name charge . a very noticeable thing about electric force is that it is large , far greater than the force of gravity . unlike gravity , however , there are two types of electric charge . opposite types of charge attract , and like types of charge repel . gravity has only one type : it only attracts , never repels . conductors and insulators conductors are made of atoms whose outer , or valence , electrons have relatively weak bonds to their nuclei , as shown in this fanciful image of a copper atom . when a bunch of metal atoms are together , they gladly share their outer electrons with each other , creating a `` swarm '' of electrons not associated with a particular nucleus . a very small electric force can make the electron swarm move . copper , gold , silver , and aluminum are good conductors . so is saltwater . there are also poor conductors . tungsten—a metal used for light bulb filaments—and carbon—used in graphite form in pencils—are relatively poor conductors because their electrons are less prone to move . insulators are materials whose outer electrons are tightly bound to their nuclei . modest electric forces are not able to pull these electrons free . when an electric force is applied , the electron clouds around the atom stretch and deform in response to the force , but the electrons do not depart . glass , plastic , stone , and air are insulators . even for insulators , though , electric force can always be turned up high enough to rip electrons away—this is called breakdown . that 's what is happening to air molecules when you see a spark . semiconductor materials fall between insulators and conductors . they usually act like insulators , but we can make them act like conductors under certain circumstances . the most well-known semiconductor material is silicon ( atomic number $ 14 $ ) . our ability to finely control the insulating and conducting properties of silicon allows us to create modern marvels like computers and mobile phones . the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current . current is reported as the number of charges per unit time passing through a boundary . visualize placing a boundary all the way through a wire . station yourself near the boundary and count the number of charges passing by . report how much charge passed through the boundary in one second . we assign a positive sign to current corresponding to the direction a positive charge would be moving . since current is the amount of charge passing through a boundary in a fixed amount of time , it can be expressed mathematically using the following equation : $ i = \dfrac { dq } { dt } $ that 's current in a nutshell . a few remarks on current what carries current in metal ? since electrons are free to move about in metals , moving electrons are what makes up the current in metals . the positive nuclei in metal atoms are fixed in place and do not contribute to current . even though electrons have a negative charge and do almost all the work in most electric circuits , we still define a positive current as the direction a positive charge would move . this is a very old historical convention . can current be carried by positive charges ? yes . there are lots of examples . current is carried by both positive and negative charges in saltwater : if we put ordinary table salt in water , it becomes a good conductor . table salt is sodium chloride , nacl . the salt dissolves in water , into free-floating na $ ^+ $ and cl $ ^- $ ions . both ions respond to electric force and move through the saltwater solution , in opposite directions . in this case , the current is composed of moving atoms , both positive and negative ions , not just loose electrons . inside our bodies , electrical currents are moving ions , both positive and negative . the same definition of current works : count the number of charges passing by in a fixed amount of time . what causes current ? charged objects move in response to electric and magnetic forces . these forces come from electric and magnetic fields , which in turn come from the position and motion of other charges . what is the speed of current ? we do n't talk very often about the speed of current . answering the question , `` how fast is the current flowing ? '' requires understanding of a complex physical phenomenon and is not often relevant . current usually is n't about meters per second , it 's about charge per second . more often , we answer the question `` how much current is flowing ? '' all the time . how do we talk about current ? when discussing current , terms like through and in make a lot of sense . current flows through a resistor ; current flows in a wire . if you hear , `` the current across ... '' , it should sound odd . voltage to get our initial toehold on the concept of voltage , let 's look at an analogy : voltage resembles gravity for a mass $ m $ , a change of height $ h $ corresponds to a change in potential energy , $ \delta u = mg\delta h $ . for a charged particle $ q $ , a voltage $ v $ corresponds to a change in potential energy , $ \delta u = qv $ . voltage in an electric circuit is analogous to the product of $ g\cdot \delta h $ . where $ g $ is the acceleration due to gravity and $ \delta h $ is the change of height . a ball at the top of the hill rolls down . when it is halfway down , it has given up half of its potential energy . an electron at the top of a voltage `` hill '' travels `` downhill '' through wires and elements of a circuit . it gives up its potential energy , doing work along the way . when the electron is halfway down the hill , it has given up , or `` dropped '' , half of its potential energy . for both the ball and the electron , the trip down the hill happens spontaneously . the ball and electron move towards a lower energy state all by themselves . on the trip down , there can be things in the way of the ball , like trees or bears to bounce off . for electrons , we can guide electrons using wires and make them flow through electronic components —circuit design— and do interesting things along the way . we can express the voltage between two points mathematically as the change of energy experienced by a charge : $ v = \dfrac { \delta u } { q } $ that 's an intuitive description of voltage in a nutshell . power power is defined as the rate energy ( $ \text u $ ) is transformed or transferred over time . we measure power in units of joules/second , also known as watts . ( $ 1 \ , \text { watt } = 1\ , \text { joule } /\text { second } $ ) $ \text { power } = \dfrac { \text du } { \text dt } $ an electric circuit is capable of transferring power . current is the rate of flow of charge , and voltage measures the energy transferred per unit of charge . we can insert these definitions into the equation for power : $ \text { power } = \dfrac { \text du } { \text dt } = \dfrac { \text du } { \text dq } \cdot \dfrac { \text dq } { \text dt } = v \ , i $ electrical power is the product of voltage times current . in units of watts . summary these mental models for current and voltage will get us started on all sorts of interesting electric circuits . if you want to reach beyond this intuitive description of voltage you can read this more formal mathematical description of electric potential and voltage .
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insulators are materials whose outer electrons are tightly bound to their nuclei . modest electric forces are not able to pull these electrons free . when an electric force is applied , the electron clouds around the atom stretch and deform in response to the force , but the electrons do not depart .
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do heat conduction and electricity conduction ruled by the same mechanics ( the free movement of electrons ) ?
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voltage and current are the cornerstone concepts in electricity . we will create our first mental models for these basic electrical quantities . we will also talk about power , which is what happens when voltage and current act together . charge the concept of electricity arises from an observation of nature . we observe a force between objects , that , like gravity , acts at a distance . the source of this force has been given the name charge . a very noticeable thing about electric force is that it is large , far greater than the force of gravity . unlike gravity , however , there are two types of electric charge . opposite types of charge attract , and like types of charge repel . gravity has only one type : it only attracts , never repels . conductors and insulators conductors are made of atoms whose outer , or valence , electrons have relatively weak bonds to their nuclei , as shown in this fanciful image of a copper atom . when a bunch of metal atoms are together , they gladly share their outer electrons with each other , creating a `` swarm '' of electrons not associated with a particular nucleus . a very small electric force can make the electron swarm move . copper , gold , silver , and aluminum are good conductors . so is saltwater . there are also poor conductors . tungsten—a metal used for light bulb filaments—and carbon—used in graphite form in pencils—are relatively poor conductors because their electrons are less prone to move . insulators are materials whose outer electrons are tightly bound to their nuclei . modest electric forces are not able to pull these electrons free . when an electric force is applied , the electron clouds around the atom stretch and deform in response to the force , but the electrons do not depart . glass , plastic , stone , and air are insulators . even for insulators , though , electric force can always be turned up high enough to rip electrons away—this is called breakdown . that 's what is happening to air molecules when you see a spark . semiconductor materials fall between insulators and conductors . they usually act like insulators , but we can make them act like conductors under certain circumstances . the most well-known semiconductor material is silicon ( atomic number $ 14 $ ) . our ability to finely control the insulating and conducting properties of silicon allows us to create modern marvels like computers and mobile phones . the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current . current is reported as the number of charges per unit time passing through a boundary . visualize placing a boundary all the way through a wire . station yourself near the boundary and count the number of charges passing by . report how much charge passed through the boundary in one second . we assign a positive sign to current corresponding to the direction a positive charge would be moving . since current is the amount of charge passing through a boundary in a fixed amount of time , it can be expressed mathematically using the following equation : $ i = \dfrac { dq } { dt } $ that 's current in a nutshell . a few remarks on current what carries current in metal ? since electrons are free to move about in metals , moving electrons are what makes up the current in metals . the positive nuclei in metal atoms are fixed in place and do not contribute to current . even though electrons have a negative charge and do almost all the work in most electric circuits , we still define a positive current as the direction a positive charge would move . this is a very old historical convention . can current be carried by positive charges ? yes . there are lots of examples . current is carried by both positive and negative charges in saltwater : if we put ordinary table salt in water , it becomes a good conductor . table salt is sodium chloride , nacl . the salt dissolves in water , into free-floating na $ ^+ $ and cl $ ^- $ ions . both ions respond to electric force and move through the saltwater solution , in opposite directions . in this case , the current is composed of moving atoms , both positive and negative ions , not just loose electrons . inside our bodies , electrical currents are moving ions , both positive and negative . the same definition of current works : count the number of charges passing by in a fixed amount of time . what causes current ? charged objects move in response to electric and magnetic forces . these forces come from electric and magnetic fields , which in turn come from the position and motion of other charges . what is the speed of current ? we do n't talk very often about the speed of current . answering the question , `` how fast is the current flowing ? '' requires understanding of a complex physical phenomenon and is not often relevant . current usually is n't about meters per second , it 's about charge per second . more often , we answer the question `` how much current is flowing ? '' all the time . how do we talk about current ? when discussing current , terms like through and in make a lot of sense . current flows through a resistor ; current flows in a wire . if you hear , `` the current across ... '' , it should sound odd . voltage to get our initial toehold on the concept of voltage , let 's look at an analogy : voltage resembles gravity for a mass $ m $ , a change of height $ h $ corresponds to a change in potential energy , $ \delta u = mg\delta h $ . for a charged particle $ q $ , a voltage $ v $ corresponds to a change in potential energy , $ \delta u = qv $ . voltage in an electric circuit is analogous to the product of $ g\cdot \delta h $ . where $ g $ is the acceleration due to gravity and $ \delta h $ is the change of height . a ball at the top of the hill rolls down . when it is halfway down , it has given up half of its potential energy . an electron at the top of a voltage `` hill '' travels `` downhill '' through wires and elements of a circuit . it gives up its potential energy , doing work along the way . when the electron is halfway down the hill , it has given up , or `` dropped '' , half of its potential energy . for both the ball and the electron , the trip down the hill happens spontaneously . the ball and electron move towards a lower energy state all by themselves . on the trip down , there can be things in the way of the ball , like trees or bears to bounce off . for electrons , we can guide electrons using wires and make them flow through electronic components —circuit design— and do interesting things along the way . we can express the voltage between two points mathematically as the change of energy experienced by a charge : $ v = \dfrac { \delta u } { q } $ that 's an intuitive description of voltage in a nutshell . power power is defined as the rate energy ( $ \text u $ ) is transformed or transferred over time . we measure power in units of joules/second , also known as watts . ( $ 1 \ , \text { watt } = 1\ , \text { joule } /\text { second } $ ) $ \text { power } = \dfrac { \text du } { \text dt } $ an electric circuit is capable of transferring power . current is the rate of flow of charge , and voltage measures the energy transferred per unit of charge . we can insert these definitions into the equation for power : $ \text { power } = \dfrac { \text du } { \text dt } = \dfrac { \text du } { \text dq } \cdot \dfrac { \text dq } { \text dt } = v \ , i $ electrical power is the product of voltage times current . in units of watts . summary these mental models for current and voltage will get us started on all sorts of interesting electric circuits . if you want to reach beyond this intuitive description of voltage you can read this more formal mathematical description of electric potential and voltage .
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a very small electric force can make the electron swarm move . copper , gold , silver , and aluminum are good conductors . so is saltwater .
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and why are copper and silver the good conductors for electricity conduction as well as for heat conduction ?
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voltage and current are the cornerstone concepts in electricity . we will create our first mental models for these basic electrical quantities . we will also talk about power , which is what happens when voltage and current act together . charge the concept of electricity arises from an observation of nature . we observe a force between objects , that , like gravity , acts at a distance . the source of this force has been given the name charge . a very noticeable thing about electric force is that it is large , far greater than the force of gravity . unlike gravity , however , there are two types of electric charge . opposite types of charge attract , and like types of charge repel . gravity has only one type : it only attracts , never repels . conductors and insulators conductors are made of atoms whose outer , or valence , electrons have relatively weak bonds to their nuclei , as shown in this fanciful image of a copper atom . when a bunch of metal atoms are together , they gladly share their outer electrons with each other , creating a `` swarm '' of electrons not associated with a particular nucleus . a very small electric force can make the electron swarm move . copper , gold , silver , and aluminum are good conductors . so is saltwater . there are also poor conductors . tungsten—a metal used for light bulb filaments—and carbon—used in graphite form in pencils—are relatively poor conductors because their electrons are less prone to move . insulators are materials whose outer electrons are tightly bound to their nuclei . modest electric forces are not able to pull these electrons free . when an electric force is applied , the electron clouds around the atom stretch and deform in response to the force , but the electrons do not depart . glass , plastic , stone , and air are insulators . even for insulators , though , electric force can always be turned up high enough to rip electrons away—this is called breakdown . that 's what is happening to air molecules when you see a spark . semiconductor materials fall between insulators and conductors . they usually act like insulators , but we can make them act like conductors under certain circumstances . the most well-known semiconductor material is silicon ( atomic number $ 14 $ ) . our ability to finely control the insulating and conducting properties of silicon allows us to create modern marvels like computers and mobile phones . the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current . current is reported as the number of charges per unit time passing through a boundary . visualize placing a boundary all the way through a wire . station yourself near the boundary and count the number of charges passing by . report how much charge passed through the boundary in one second . we assign a positive sign to current corresponding to the direction a positive charge would be moving . since current is the amount of charge passing through a boundary in a fixed amount of time , it can be expressed mathematically using the following equation : $ i = \dfrac { dq } { dt } $ that 's current in a nutshell . a few remarks on current what carries current in metal ? since electrons are free to move about in metals , moving electrons are what makes up the current in metals . the positive nuclei in metal atoms are fixed in place and do not contribute to current . even though electrons have a negative charge and do almost all the work in most electric circuits , we still define a positive current as the direction a positive charge would move . this is a very old historical convention . can current be carried by positive charges ? yes . there are lots of examples . current is carried by both positive and negative charges in saltwater : if we put ordinary table salt in water , it becomes a good conductor . table salt is sodium chloride , nacl . the salt dissolves in water , into free-floating na $ ^+ $ and cl $ ^- $ ions . both ions respond to electric force and move through the saltwater solution , in opposite directions . in this case , the current is composed of moving atoms , both positive and negative ions , not just loose electrons . inside our bodies , electrical currents are moving ions , both positive and negative . the same definition of current works : count the number of charges passing by in a fixed amount of time . what causes current ? charged objects move in response to electric and magnetic forces . these forces come from electric and magnetic fields , which in turn come from the position and motion of other charges . what is the speed of current ? we do n't talk very often about the speed of current . answering the question , `` how fast is the current flowing ? '' requires understanding of a complex physical phenomenon and is not often relevant . current usually is n't about meters per second , it 's about charge per second . more often , we answer the question `` how much current is flowing ? '' all the time . how do we talk about current ? when discussing current , terms like through and in make a lot of sense . current flows through a resistor ; current flows in a wire . if you hear , `` the current across ... '' , it should sound odd . voltage to get our initial toehold on the concept of voltage , let 's look at an analogy : voltage resembles gravity for a mass $ m $ , a change of height $ h $ corresponds to a change in potential energy , $ \delta u = mg\delta h $ . for a charged particle $ q $ , a voltage $ v $ corresponds to a change in potential energy , $ \delta u = qv $ . voltage in an electric circuit is analogous to the product of $ g\cdot \delta h $ . where $ g $ is the acceleration due to gravity and $ \delta h $ is the change of height . a ball at the top of the hill rolls down . when it is halfway down , it has given up half of its potential energy . an electron at the top of a voltage `` hill '' travels `` downhill '' through wires and elements of a circuit . it gives up its potential energy , doing work along the way . when the electron is halfway down the hill , it has given up , or `` dropped '' , half of its potential energy . for both the ball and the electron , the trip down the hill happens spontaneously . the ball and electron move towards a lower energy state all by themselves . on the trip down , there can be things in the way of the ball , like trees or bears to bounce off . for electrons , we can guide electrons using wires and make them flow through electronic components —circuit design— and do interesting things along the way . we can express the voltage between two points mathematically as the change of energy experienced by a charge : $ v = \dfrac { \delta u } { q } $ that 's an intuitive description of voltage in a nutshell . power power is defined as the rate energy ( $ \text u $ ) is transformed or transferred over time . we measure power in units of joules/second , also known as watts . ( $ 1 \ , \text { watt } = 1\ , \text { joule } /\text { second } $ ) $ \text { power } = \dfrac { \text du } { \text dt } $ an electric circuit is capable of transferring power . current is the rate of flow of charge , and voltage measures the energy transferred per unit of charge . we can insert these definitions into the equation for power : $ \text { power } = \dfrac { \text du } { \text dt } = \dfrac { \text du } { \text dq } \cdot \dfrac { \text dq } { \text dt } = v \ , i $ electrical power is the product of voltage times current . in units of watts . summary these mental models for current and voltage will get us started on all sorts of interesting electric circuits . if you want to reach beyond this intuitive description of voltage you can read this more formal mathematical description of electric potential and voltage .
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for a charged particle $ q $ , a voltage $ v $ corresponds to a change in potential energy , $ \delta u = qv $ . voltage in an electric circuit is analogous to the product of $ g\cdot \delta h $ . where $ g $ is the acceleration due to gravity and $ \delta h $ is the change of height .
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is it possible to have a circuit in which the p.d across the terminals of a battery in the circuit is zero ?
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voltage and current are the cornerstone concepts in electricity . we will create our first mental models for these basic electrical quantities . we will also talk about power , which is what happens when voltage and current act together . charge the concept of electricity arises from an observation of nature . we observe a force between objects , that , like gravity , acts at a distance . the source of this force has been given the name charge . a very noticeable thing about electric force is that it is large , far greater than the force of gravity . unlike gravity , however , there are two types of electric charge . opposite types of charge attract , and like types of charge repel . gravity has only one type : it only attracts , never repels . conductors and insulators conductors are made of atoms whose outer , or valence , electrons have relatively weak bonds to their nuclei , as shown in this fanciful image of a copper atom . when a bunch of metal atoms are together , they gladly share their outer electrons with each other , creating a `` swarm '' of electrons not associated with a particular nucleus . a very small electric force can make the electron swarm move . copper , gold , silver , and aluminum are good conductors . so is saltwater . there are also poor conductors . tungsten—a metal used for light bulb filaments—and carbon—used in graphite form in pencils—are relatively poor conductors because their electrons are less prone to move . insulators are materials whose outer electrons are tightly bound to their nuclei . modest electric forces are not able to pull these electrons free . when an electric force is applied , the electron clouds around the atom stretch and deform in response to the force , but the electrons do not depart . glass , plastic , stone , and air are insulators . even for insulators , though , electric force can always be turned up high enough to rip electrons away—this is called breakdown . that 's what is happening to air molecules when you see a spark . semiconductor materials fall between insulators and conductors . they usually act like insulators , but we can make them act like conductors under certain circumstances . the most well-known semiconductor material is silicon ( atomic number $ 14 $ ) . our ability to finely control the insulating and conducting properties of silicon allows us to create modern marvels like computers and mobile phones . the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current . current is reported as the number of charges per unit time passing through a boundary . visualize placing a boundary all the way through a wire . station yourself near the boundary and count the number of charges passing by . report how much charge passed through the boundary in one second . we assign a positive sign to current corresponding to the direction a positive charge would be moving . since current is the amount of charge passing through a boundary in a fixed amount of time , it can be expressed mathematically using the following equation : $ i = \dfrac { dq } { dt } $ that 's current in a nutshell . a few remarks on current what carries current in metal ? since electrons are free to move about in metals , moving electrons are what makes up the current in metals . the positive nuclei in metal atoms are fixed in place and do not contribute to current . even though electrons have a negative charge and do almost all the work in most electric circuits , we still define a positive current as the direction a positive charge would move . this is a very old historical convention . can current be carried by positive charges ? yes . there are lots of examples . current is carried by both positive and negative charges in saltwater : if we put ordinary table salt in water , it becomes a good conductor . table salt is sodium chloride , nacl . the salt dissolves in water , into free-floating na $ ^+ $ and cl $ ^- $ ions . both ions respond to electric force and move through the saltwater solution , in opposite directions . in this case , the current is composed of moving atoms , both positive and negative ions , not just loose electrons . inside our bodies , electrical currents are moving ions , both positive and negative . the same definition of current works : count the number of charges passing by in a fixed amount of time . what causes current ? charged objects move in response to electric and magnetic forces . these forces come from electric and magnetic fields , which in turn come from the position and motion of other charges . what is the speed of current ? we do n't talk very often about the speed of current . answering the question , `` how fast is the current flowing ? '' requires understanding of a complex physical phenomenon and is not often relevant . current usually is n't about meters per second , it 's about charge per second . more often , we answer the question `` how much current is flowing ? '' all the time . how do we talk about current ? when discussing current , terms like through and in make a lot of sense . current flows through a resistor ; current flows in a wire . if you hear , `` the current across ... '' , it should sound odd . voltage to get our initial toehold on the concept of voltage , let 's look at an analogy : voltage resembles gravity for a mass $ m $ , a change of height $ h $ corresponds to a change in potential energy , $ \delta u = mg\delta h $ . for a charged particle $ q $ , a voltage $ v $ corresponds to a change in potential energy , $ \delta u = qv $ . voltage in an electric circuit is analogous to the product of $ g\cdot \delta h $ . where $ g $ is the acceleration due to gravity and $ \delta h $ is the change of height . a ball at the top of the hill rolls down . when it is halfway down , it has given up half of its potential energy . an electron at the top of a voltage `` hill '' travels `` downhill '' through wires and elements of a circuit . it gives up its potential energy , doing work along the way . when the electron is halfway down the hill , it has given up , or `` dropped '' , half of its potential energy . for both the ball and the electron , the trip down the hill happens spontaneously . the ball and electron move towards a lower energy state all by themselves . on the trip down , there can be things in the way of the ball , like trees or bears to bounce off . for electrons , we can guide electrons using wires and make them flow through electronic components —circuit design— and do interesting things along the way . we can express the voltage between two points mathematically as the change of energy experienced by a charge : $ v = \dfrac { \delta u } { q } $ that 's an intuitive description of voltage in a nutshell . power power is defined as the rate energy ( $ \text u $ ) is transformed or transferred over time . we measure power in units of joules/second , also known as watts . ( $ 1 \ , \text { watt } = 1\ , \text { joule } /\text { second } $ ) $ \text { power } = \dfrac { \text du } { \text dt } $ an electric circuit is capable of transferring power . current is the rate of flow of charge , and voltage measures the energy transferred per unit of charge . we can insert these definitions into the equation for power : $ \text { power } = \dfrac { \text du } { \text dt } = \dfrac { \text du } { \text dq } \cdot \dfrac { \text dq } { \text dt } = v \ , i $ electrical power is the product of voltage times current . in units of watts . summary these mental models for current and voltage will get us started on all sorts of interesting electric circuits . if you want to reach beyond this intuitive description of voltage you can read this more formal mathematical description of electric potential and voltage .
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copper , gold , silver , and aluminum are good conductors . so is saltwater . there are also poor conductors .
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how is saltwater a conducter ?
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voltage and current are the cornerstone concepts in electricity . we will create our first mental models for these basic electrical quantities . we will also talk about power , which is what happens when voltage and current act together . charge the concept of electricity arises from an observation of nature . we observe a force between objects , that , like gravity , acts at a distance . the source of this force has been given the name charge . a very noticeable thing about electric force is that it is large , far greater than the force of gravity . unlike gravity , however , there are two types of electric charge . opposite types of charge attract , and like types of charge repel . gravity has only one type : it only attracts , never repels . conductors and insulators conductors are made of atoms whose outer , or valence , electrons have relatively weak bonds to their nuclei , as shown in this fanciful image of a copper atom . when a bunch of metal atoms are together , they gladly share their outer electrons with each other , creating a `` swarm '' of electrons not associated with a particular nucleus . a very small electric force can make the electron swarm move . copper , gold , silver , and aluminum are good conductors . so is saltwater . there are also poor conductors . tungsten—a metal used for light bulb filaments—and carbon—used in graphite form in pencils—are relatively poor conductors because their electrons are less prone to move . insulators are materials whose outer electrons are tightly bound to their nuclei . modest electric forces are not able to pull these electrons free . when an electric force is applied , the electron clouds around the atom stretch and deform in response to the force , but the electrons do not depart . glass , plastic , stone , and air are insulators . even for insulators , though , electric force can always be turned up high enough to rip electrons away—this is called breakdown . that 's what is happening to air molecules when you see a spark . semiconductor materials fall between insulators and conductors . they usually act like insulators , but we can make them act like conductors under certain circumstances . the most well-known semiconductor material is silicon ( atomic number $ 14 $ ) . our ability to finely control the insulating and conducting properties of silicon allows us to create modern marvels like computers and mobile phones . the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current . current is reported as the number of charges per unit time passing through a boundary . visualize placing a boundary all the way through a wire . station yourself near the boundary and count the number of charges passing by . report how much charge passed through the boundary in one second . we assign a positive sign to current corresponding to the direction a positive charge would be moving . since current is the amount of charge passing through a boundary in a fixed amount of time , it can be expressed mathematically using the following equation : $ i = \dfrac { dq } { dt } $ that 's current in a nutshell . a few remarks on current what carries current in metal ? since electrons are free to move about in metals , moving electrons are what makes up the current in metals . the positive nuclei in metal atoms are fixed in place and do not contribute to current . even though electrons have a negative charge and do almost all the work in most electric circuits , we still define a positive current as the direction a positive charge would move . this is a very old historical convention . can current be carried by positive charges ? yes . there are lots of examples . current is carried by both positive and negative charges in saltwater : if we put ordinary table salt in water , it becomes a good conductor . table salt is sodium chloride , nacl . the salt dissolves in water , into free-floating na $ ^+ $ and cl $ ^- $ ions . both ions respond to electric force and move through the saltwater solution , in opposite directions . in this case , the current is composed of moving atoms , both positive and negative ions , not just loose electrons . inside our bodies , electrical currents are moving ions , both positive and negative . the same definition of current works : count the number of charges passing by in a fixed amount of time . what causes current ? charged objects move in response to electric and magnetic forces . these forces come from electric and magnetic fields , which in turn come from the position and motion of other charges . what is the speed of current ? we do n't talk very often about the speed of current . answering the question , `` how fast is the current flowing ? '' requires understanding of a complex physical phenomenon and is not often relevant . current usually is n't about meters per second , it 's about charge per second . more often , we answer the question `` how much current is flowing ? '' all the time . how do we talk about current ? when discussing current , terms like through and in make a lot of sense . current flows through a resistor ; current flows in a wire . if you hear , `` the current across ... '' , it should sound odd . voltage to get our initial toehold on the concept of voltage , let 's look at an analogy : voltage resembles gravity for a mass $ m $ , a change of height $ h $ corresponds to a change in potential energy , $ \delta u = mg\delta h $ . for a charged particle $ q $ , a voltage $ v $ corresponds to a change in potential energy , $ \delta u = qv $ . voltage in an electric circuit is analogous to the product of $ g\cdot \delta h $ . where $ g $ is the acceleration due to gravity and $ \delta h $ is the change of height . a ball at the top of the hill rolls down . when it is halfway down , it has given up half of its potential energy . an electron at the top of a voltage `` hill '' travels `` downhill '' through wires and elements of a circuit . it gives up its potential energy , doing work along the way . when the electron is halfway down the hill , it has given up , or `` dropped '' , half of its potential energy . for both the ball and the electron , the trip down the hill happens spontaneously . the ball and electron move towards a lower energy state all by themselves . on the trip down , there can be things in the way of the ball , like trees or bears to bounce off . for electrons , we can guide electrons using wires and make them flow through electronic components —circuit design— and do interesting things along the way . we can express the voltage between two points mathematically as the change of energy experienced by a charge : $ v = \dfrac { \delta u } { q } $ that 's an intuitive description of voltage in a nutshell . power power is defined as the rate energy ( $ \text u $ ) is transformed or transferred over time . we measure power in units of joules/second , also known as watts . ( $ 1 \ , \text { watt } = 1\ , \text { joule } /\text { second } $ ) $ \text { power } = \dfrac { \text du } { \text dt } $ an electric circuit is capable of transferring power . current is the rate of flow of charge , and voltage measures the energy transferred per unit of charge . we can insert these definitions into the equation for power : $ \text { power } = \dfrac { \text du } { \text dt } = \dfrac { \text du } { \text dq } \cdot \dfrac { \text dq } { \text dt } = v \ , i $ electrical power is the product of voltage times current . in units of watts . summary these mental models for current and voltage will get us started on all sorts of interesting electric circuits . if you want to reach beyond this intuitive description of voltage you can read this more formal mathematical description of electric potential and voltage .
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voltage to get our initial toehold on the concept of voltage , let 's look at an analogy : voltage resembles gravity for a mass $ m $ , a change of height $ h $ corresponds to a change in potential energy , $ \delta u = mg\delta h $ . for a charged particle $ q $ , a voltage $ v $ corresponds to a change in potential energy , $ \delta u = qv $ . voltage in an electric circuit is analogous to the product of $ g\cdot \delta h $ .
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if 'u ' is potential energy , 'q ' is charge , and 't ' is time what is 'd ' ?
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voltage and current are the cornerstone concepts in electricity . we will create our first mental models for these basic electrical quantities . we will also talk about power , which is what happens when voltage and current act together . charge the concept of electricity arises from an observation of nature . we observe a force between objects , that , like gravity , acts at a distance . the source of this force has been given the name charge . a very noticeable thing about electric force is that it is large , far greater than the force of gravity . unlike gravity , however , there are two types of electric charge . opposite types of charge attract , and like types of charge repel . gravity has only one type : it only attracts , never repels . conductors and insulators conductors are made of atoms whose outer , or valence , electrons have relatively weak bonds to their nuclei , as shown in this fanciful image of a copper atom . when a bunch of metal atoms are together , they gladly share their outer electrons with each other , creating a `` swarm '' of electrons not associated with a particular nucleus . a very small electric force can make the electron swarm move . copper , gold , silver , and aluminum are good conductors . so is saltwater . there are also poor conductors . tungsten—a metal used for light bulb filaments—and carbon—used in graphite form in pencils—are relatively poor conductors because their electrons are less prone to move . insulators are materials whose outer electrons are tightly bound to their nuclei . modest electric forces are not able to pull these electrons free . when an electric force is applied , the electron clouds around the atom stretch and deform in response to the force , but the electrons do not depart . glass , plastic , stone , and air are insulators . even for insulators , though , electric force can always be turned up high enough to rip electrons away—this is called breakdown . that 's what is happening to air molecules when you see a spark . semiconductor materials fall between insulators and conductors . they usually act like insulators , but we can make them act like conductors under certain circumstances . the most well-known semiconductor material is silicon ( atomic number $ 14 $ ) . our ability to finely control the insulating and conducting properties of silicon allows us to create modern marvels like computers and mobile phones . the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current . current is reported as the number of charges per unit time passing through a boundary . visualize placing a boundary all the way through a wire . station yourself near the boundary and count the number of charges passing by . report how much charge passed through the boundary in one second . we assign a positive sign to current corresponding to the direction a positive charge would be moving . since current is the amount of charge passing through a boundary in a fixed amount of time , it can be expressed mathematically using the following equation : $ i = \dfrac { dq } { dt } $ that 's current in a nutshell . a few remarks on current what carries current in metal ? since electrons are free to move about in metals , moving electrons are what makes up the current in metals . the positive nuclei in metal atoms are fixed in place and do not contribute to current . even though electrons have a negative charge and do almost all the work in most electric circuits , we still define a positive current as the direction a positive charge would move . this is a very old historical convention . can current be carried by positive charges ? yes . there are lots of examples . current is carried by both positive and negative charges in saltwater : if we put ordinary table salt in water , it becomes a good conductor . table salt is sodium chloride , nacl . the salt dissolves in water , into free-floating na $ ^+ $ and cl $ ^- $ ions . both ions respond to electric force and move through the saltwater solution , in opposite directions . in this case , the current is composed of moving atoms , both positive and negative ions , not just loose electrons . inside our bodies , electrical currents are moving ions , both positive and negative . the same definition of current works : count the number of charges passing by in a fixed amount of time . what causes current ? charged objects move in response to electric and magnetic forces . these forces come from electric and magnetic fields , which in turn come from the position and motion of other charges . what is the speed of current ? we do n't talk very often about the speed of current . answering the question , `` how fast is the current flowing ? '' requires understanding of a complex physical phenomenon and is not often relevant . current usually is n't about meters per second , it 's about charge per second . more often , we answer the question `` how much current is flowing ? '' all the time . how do we talk about current ? when discussing current , terms like through and in make a lot of sense . current flows through a resistor ; current flows in a wire . if you hear , `` the current across ... '' , it should sound odd . voltage to get our initial toehold on the concept of voltage , let 's look at an analogy : voltage resembles gravity for a mass $ m $ , a change of height $ h $ corresponds to a change in potential energy , $ \delta u = mg\delta h $ . for a charged particle $ q $ , a voltage $ v $ corresponds to a change in potential energy , $ \delta u = qv $ . voltage in an electric circuit is analogous to the product of $ g\cdot \delta h $ . where $ g $ is the acceleration due to gravity and $ \delta h $ is the change of height . a ball at the top of the hill rolls down . when it is halfway down , it has given up half of its potential energy . an electron at the top of a voltage `` hill '' travels `` downhill '' through wires and elements of a circuit . it gives up its potential energy , doing work along the way . when the electron is halfway down the hill , it has given up , or `` dropped '' , half of its potential energy . for both the ball and the electron , the trip down the hill happens spontaneously . the ball and electron move towards a lower energy state all by themselves . on the trip down , there can be things in the way of the ball , like trees or bears to bounce off . for electrons , we can guide electrons using wires and make them flow through electronic components —circuit design— and do interesting things along the way . we can express the voltage between two points mathematically as the change of energy experienced by a charge : $ v = \dfrac { \delta u } { q } $ that 's an intuitive description of voltage in a nutshell . power power is defined as the rate energy ( $ \text u $ ) is transformed or transferred over time . we measure power in units of joules/second , also known as watts . ( $ 1 \ , \text { watt } = 1\ , \text { joule } /\text { second } $ ) $ \text { power } = \dfrac { \text du } { \text dt } $ an electric circuit is capable of transferring power . current is the rate of flow of charge , and voltage measures the energy transferred per unit of charge . we can insert these definitions into the equation for power : $ \text { power } = \dfrac { \text du } { \text dt } = \dfrac { \text du } { \text dq } \cdot \dfrac { \text dq } { \text dt } = v \ , i $ electrical power is the product of voltage times current . in units of watts . summary these mental models for current and voltage will get us started on all sorts of interesting electric circuits . if you want to reach beyond this intuitive description of voltage you can read this more formal mathematical description of electric potential and voltage .
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there are lots of examples . current is carried by both positive and negative charges in saltwater : if we put ordinary table salt in water , it becomes a good conductor . table salt is sodium chloride , nacl .
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is the sun a good conductor of energy ?
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voltage and current are the cornerstone concepts in electricity . we will create our first mental models for these basic electrical quantities . we will also talk about power , which is what happens when voltage and current act together . charge the concept of electricity arises from an observation of nature . we observe a force between objects , that , like gravity , acts at a distance . the source of this force has been given the name charge . a very noticeable thing about electric force is that it is large , far greater than the force of gravity . unlike gravity , however , there are two types of electric charge . opposite types of charge attract , and like types of charge repel . gravity has only one type : it only attracts , never repels . conductors and insulators conductors are made of atoms whose outer , or valence , electrons have relatively weak bonds to their nuclei , as shown in this fanciful image of a copper atom . when a bunch of metal atoms are together , they gladly share their outer electrons with each other , creating a `` swarm '' of electrons not associated with a particular nucleus . a very small electric force can make the electron swarm move . copper , gold , silver , and aluminum are good conductors . so is saltwater . there are also poor conductors . tungsten—a metal used for light bulb filaments—and carbon—used in graphite form in pencils—are relatively poor conductors because their electrons are less prone to move . insulators are materials whose outer electrons are tightly bound to their nuclei . modest electric forces are not able to pull these electrons free . when an electric force is applied , the electron clouds around the atom stretch and deform in response to the force , but the electrons do not depart . glass , plastic , stone , and air are insulators . even for insulators , though , electric force can always be turned up high enough to rip electrons away—this is called breakdown . that 's what is happening to air molecules when you see a spark . semiconductor materials fall between insulators and conductors . they usually act like insulators , but we can make them act like conductors under certain circumstances . the most well-known semiconductor material is silicon ( atomic number $ 14 $ ) . our ability to finely control the insulating and conducting properties of silicon allows us to create modern marvels like computers and mobile phones . the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current . current is reported as the number of charges per unit time passing through a boundary . visualize placing a boundary all the way through a wire . station yourself near the boundary and count the number of charges passing by . report how much charge passed through the boundary in one second . we assign a positive sign to current corresponding to the direction a positive charge would be moving . since current is the amount of charge passing through a boundary in a fixed amount of time , it can be expressed mathematically using the following equation : $ i = \dfrac { dq } { dt } $ that 's current in a nutshell . a few remarks on current what carries current in metal ? since electrons are free to move about in metals , moving electrons are what makes up the current in metals . the positive nuclei in metal atoms are fixed in place and do not contribute to current . even though electrons have a negative charge and do almost all the work in most electric circuits , we still define a positive current as the direction a positive charge would move . this is a very old historical convention . can current be carried by positive charges ? yes . there are lots of examples . current is carried by both positive and negative charges in saltwater : if we put ordinary table salt in water , it becomes a good conductor . table salt is sodium chloride , nacl . the salt dissolves in water , into free-floating na $ ^+ $ and cl $ ^- $ ions . both ions respond to electric force and move through the saltwater solution , in opposite directions . in this case , the current is composed of moving atoms , both positive and negative ions , not just loose electrons . inside our bodies , electrical currents are moving ions , both positive and negative . the same definition of current works : count the number of charges passing by in a fixed amount of time . what causes current ? charged objects move in response to electric and magnetic forces . these forces come from electric and magnetic fields , which in turn come from the position and motion of other charges . what is the speed of current ? we do n't talk very often about the speed of current . answering the question , `` how fast is the current flowing ? '' requires understanding of a complex physical phenomenon and is not often relevant . current usually is n't about meters per second , it 's about charge per second . more often , we answer the question `` how much current is flowing ? '' all the time . how do we talk about current ? when discussing current , terms like through and in make a lot of sense . current flows through a resistor ; current flows in a wire . if you hear , `` the current across ... '' , it should sound odd . voltage to get our initial toehold on the concept of voltage , let 's look at an analogy : voltage resembles gravity for a mass $ m $ , a change of height $ h $ corresponds to a change in potential energy , $ \delta u = mg\delta h $ . for a charged particle $ q $ , a voltage $ v $ corresponds to a change in potential energy , $ \delta u = qv $ . voltage in an electric circuit is analogous to the product of $ g\cdot \delta h $ . where $ g $ is the acceleration due to gravity and $ \delta h $ is the change of height . a ball at the top of the hill rolls down . when it is halfway down , it has given up half of its potential energy . an electron at the top of a voltage `` hill '' travels `` downhill '' through wires and elements of a circuit . it gives up its potential energy , doing work along the way . when the electron is halfway down the hill , it has given up , or `` dropped '' , half of its potential energy . for both the ball and the electron , the trip down the hill happens spontaneously . the ball and electron move towards a lower energy state all by themselves . on the trip down , there can be things in the way of the ball , like trees or bears to bounce off . for electrons , we can guide electrons using wires and make them flow through electronic components —circuit design— and do interesting things along the way . we can express the voltage between two points mathematically as the change of energy experienced by a charge : $ v = \dfrac { \delta u } { q } $ that 's an intuitive description of voltage in a nutshell . power power is defined as the rate energy ( $ \text u $ ) is transformed or transferred over time . we measure power in units of joules/second , also known as watts . ( $ 1 \ , \text { watt } = 1\ , \text { joule } /\text { second } $ ) $ \text { power } = \dfrac { \text du } { \text dt } $ an electric circuit is capable of transferring power . current is the rate of flow of charge , and voltage measures the energy transferred per unit of charge . we can insert these definitions into the equation for power : $ \text { power } = \dfrac { \text du } { \text dt } = \dfrac { \text du } { \text dq } \cdot \dfrac { \text dq } { \text dt } = v \ , i $ electrical power is the product of voltage times current . in units of watts . summary these mental models for current and voltage will get us started on all sorts of interesting electric circuits . if you want to reach beyond this intuitive description of voltage you can read this more formal mathematical description of electric potential and voltage .
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for a charged particle $ q $ , a voltage $ v $ corresponds to a change in potential energy , $ \delta u = qv $ . voltage in an electric circuit is analogous to the product of $ g\cdot \delta h $ . where $ g $ is the acceleration due to gravity and $ \delta h $ is the change of height .
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what is a series and parallel circuit ?
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voltage and current are the cornerstone concepts in electricity . we will create our first mental models for these basic electrical quantities . we will also talk about power , which is what happens when voltage and current act together . charge the concept of electricity arises from an observation of nature . we observe a force between objects , that , like gravity , acts at a distance . the source of this force has been given the name charge . a very noticeable thing about electric force is that it is large , far greater than the force of gravity . unlike gravity , however , there are two types of electric charge . opposite types of charge attract , and like types of charge repel . gravity has only one type : it only attracts , never repels . conductors and insulators conductors are made of atoms whose outer , or valence , electrons have relatively weak bonds to their nuclei , as shown in this fanciful image of a copper atom . when a bunch of metal atoms are together , they gladly share their outer electrons with each other , creating a `` swarm '' of electrons not associated with a particular nucleus . a very small electric force can make the electron swarm move . copper , gold , silver , and aluminum are good conductors . so is saltwater . there are also poor conductors . tungsten—a metal used for light bulb filaments—and carbon—used in graphite form in pencils—are relatively poor conductors because their electrons are less prone to move . insulators are materials whose outer electrons are tightly bound to their nuclei . modest electric forces are not able to pull these electrons free . when an electric force is applied , the electron clouds around the atom stretch and deform in response to the force , but the electrons do not depart . glass , plastic , stone , and air are insulators . even for insulators , though , electric force can always be turned up high enough to rip electrons away—this is called breakdown . that 's what is happening to air molecules when you see a spark . semiconductor materials fall between insulators and conductors . they usually act like insulators , but we can make them act like conductors under certain circumstances . the most well-known semiconductor material is silicon ( atomic number $ 14 $ ) . our ability to finely control the insulating and conducting properties of silicon allows us to create modern marvels like computers and mobile phones . the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current . current is reported as the number of charges per unit time passing through a boundary . visualize placing a boundary all the way through a wire . station yourself near the boundary and count the number of charges passing by . report how much charge passed through the boundary in one second . we assign a positive sign to current corresponding to the direction a positive charge would be moving . since current is the amount of charge passing through a boundary in a fixed amount of time , it can be expressed mathematically using the following equation : $ i = \dfrac { dq } { dt } $ that 's current in a nutshell . a few remarks on current what carries current in metal ? since electrons are free to move about in metals , moving electrons are what makes up the current in metals . the positive nuclei in metal atoms are fixed in place and do not contribute to current . even though electrons have a negative charge and do almost all the work in most electric circuits , we still define a positive current as the direction a positive charge would move . this is a very old historical convention . can current be carried by positive charges ? yes . there are lots of examples . current is carried by both positive and negative charges in saltwater : if we put ordinary table salt in water , it becomes a good conductor . table salt is sodium chloride , nacl . the salt dissolves in water , into free-floating na $ ^+ $ and cl $ ^- $ ions . both ions respond to electric force and move through the saltwater solution , in opposite directions . in this case , the current is composed of moving atoms , both positive and negative ions , not just loose electrons . inside our bodies , electrical currents are moving ions , both positive and negative . the same definition of current works : count the number of charges passing by in a fixed amount of time . what causes current ? charged objects move in response to electric and magnetic forces . these forces come from electric and magnetic fields , which in turn come from the position and motion of other charges . what is the speed of current ? we do n't talk very often about the speed of current . answering the question , `` how fast is the current flowing ? '' requires understanding of a complex physical phenomenon and is not often relevant . current usually is n't about meters per second , it 's about charge per second . more often , we answer the question `` how much current is flowing ? '' all the time . how do we talk about current ? when discussing current , terms like through and in make a lot of sense . current flows through a resistor ; current flows in a wire . if you hear , `` the current across ... '' , it should sound odd . voltage to get our initial toehold on the concept of voltage , let 's look at an analogy : voltage resembles gravity for a mass $ m $ , a change of height $ h $ corresponds to a change in potential energy , $ \delta u = mg\delta h $ . for a charged particle $ q $ , a voltage $ v $ corresponds to a change in potential energy , $ \delta u = qv $ . voltage in an electric circuit is analogous to the product of $ g\cdot \delta h $ . where $ g $ is the acceleration due to gravity and $ \delta h $ is the change of height . a ball at the top of the hill rolls down . when it is halfway down , it has given up half of its potential energy . an electron at the top of a voltage `` hill '' travels `` downhill '' through wires and elements of a circuit . it gives up its potential energy , doing work along the way . when the electron is halfway down the hill , it has given up , or `` dropped '' , half of its potential energy . for both the ball and the electron , the trip down the hill happens spontaneously . the ball and electron move towards a lower energy state all by themselves . on the trip down , there can be things in the way of the ball , like trees or bears to bounce off . for electrons , we can guide electrons using wires and make them flow through electronic components —circuit design— and do interesting things along the way . we can express the voltage between two points mathematically as the change of energy experienced by a charge : $ v = \dfrac { \delta u } { q } $ that 's an intuitive description of voltage in a nutshell . power power is defined as the rate energy ( $ \text u $ ) is transformed or transferred over time . we measure power in units of joules/second , also known as watts . ( $ 1 \ , \text { watt } = 1\ , \text { joule } /\text { second } $ ) $ \text { power } = \dfrac { \text du } { \text dt } $ an electric circuit is capable of transferring power . current is the rate of flow of charge , and voltage measures the energy transferred per unit of charge . we can insert these definitions into the equation for power : $ \text { power } = \dfrac { \text du } { \text dt } = \dfrac { \text du } { \text dq } \cdot \dfrac { \text dq } { \text dt } = v \ , i $ electrical power is the product of voltage times current . in units of watts . summary these mental models for current and voltage will get us started on all sorts of interesting electric circuits . if you want to reach beyond this intuitive description of voltage you can read this more formal mathematical description of electric potential and voltage .
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a ball at the top of the hill rolls down . when it is halfway down , it has given up half of its potential energy . an electron at the top of a voltage `` hill '' travels `` downhill '' through wires and elements of a circuit . it gives up its potential energy , doing work along the way . when the electron is halfway down the hill , it has given up , or `` dropped '' , half of its potential energy .
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when an electron travels through a wire due to voltage , does the electrical potential energy also turns into kinetic energy ?
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voltage and current are the cornerstone concepts in electricity . we will create our first mental models for these basic electrical quantities . we will also talk about power , which is what happens when voltage and current act together . charge the concept of electricity arises from an observation of nature . we observe a force between objects , that , like gravity , acts at a distance . the source of this force has been given the name charge . a very noticeable thing about electric force is that it is large , far greater than the force of gravity . unlike gravity , however , there are two types of electric charge . opposite types of charge attract , and like types of charge repel . gravity has only one type : it only attracts , never repels . conductors and insulators conductors are made of atoms whose outer , or valence , electrons have relatively weak bonds to their nuclei , as shown in this fanciful image of a copper atom . when a bunch of metal atoms are together , they gladly share their outer electrons with each other , creating a `` swarm '' of electrons not associated with a particular nucleus . a very small electric force can make the electron swarm move . copper , gold , silver , and aluminum are good conductors . so is saltwater . there are also poor conductors . tungsten—a metal used for light bulb filaments—and carbon—used in graphite form in pencils—are relatively poor conductors because their electrons are less prone to move . insulators are materials whose outer electrons are tightly bound to their nuclei . modest electric forces are not able to pull these electrons free . when an electric force is applied , the electron clouds around the atom stretch and deform in response to the force , but the electrons do not depart . glass , plastic , stone , and air are insulators . even for insulators , though , electric force can always be turned up high enough to rip electrons away—this is called breakdown . that 's what is happening to air molecules when you see a spark . semiconductor materials fall between insulators and conductors . they usually act like insulators , but we can make them act like conductors under certain circumstances . the most well-known semiconductor material is silicon ( atomic number $ 14 $ ) . our ability to finely control the insulating and conducting properties of silicon allows us to create modern marvels like computers and mobile phones . the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current . current is reported as the number of charges per unit time passing through a boundary . visualize placing a boundary all the way through a wire . station yourself near the boundary and count the number of charges passing by . report how much charge passed through the boundary in one second . we assign a positive sign to current corresponding to the direction a positive charge would be moving . since current is the amount of charge passing through a boundary in a fixed amount of time , it can be expressed mathematically using the following equation : $ i = \dfrac { dq } { dt } $ that 's current in a nutshell . a few remarks on current what carries current in metal ? since electrons are free to move about in metals , moving electrons are what makes up the current in metals . the positive nuclei in metal atoms are fixed in place and do not contribute to current . even though electrons have a negative charge and do almost all the work in most electric circuits , we still define a positive current as the direction a positive charge would move . this is a very old historical convention . can current be carried by positive charges ? yes . there are lots of examples . current is carried by both positive and negative charges in saltwater : if we put ordinary table salt in water , it becomes a good conductor . table salt is sodium chloride , nacl . the salt dissolves in water , into free-floating na $ ^+ $ and cl $ ^- $ ions . both ions respond to electric force and move through the saltwater solution , in opposite directions . in this case , the current is composed of moving atoms , both positive and negative ions , not just loose electrons . inside our bodies , electrical currents are moving ions , both positive and negative . the same definition of current works : count the number of charges passing by in a fixed amount of time . what causes current ? charged objects move in response to electric and magnetic forces . these forces come from electric and magnetic fields , which in turn come from the position and motion of other charges . what is the speed of current ? we do n't talk very often about the speed of current . answering the question , `` how fast is the current flowing ? '' requires understanding of a complex physical phenomenon and is not often relevant . current usually is n't about meters per second , it 's about charge per second . more often , we answer the question `` how much current is flowing ? '' all the time . how do we talk about current ? when discussing current , terms like through and in make a lot of sense . current flows through a resistor ; current flows in a wire . if you hear , `` the current across ... '' , it should sound odd . voltage to get our initial toehold on the concept of voltage , let 's look at an analogy : voltage resembles gravity for a mass $ m $ , a change of height $ h $ corresponds to a change in potential energy , $ \delta u = mg\delta h $ . for a charged particle $ q $ , a voltage $ v $ corresponds to a change in potential energy , $ \delta u = qv $ . voltage in an electric circuit is analogous to the product of $ g\cdot \delta h $ . where $ g $ is the acceleration due to gravity and $ \delta h $ is the change of height . a ball at the top of the hill rolls down . when it is halfway down , it has given up half of its potential energy . an electron at the top of a voltage `` hill '' travels `` downhill '' through wires and elements of a circuit . it gives up its potential energy , doing work along the way . when the electron is halfway down the hill , it has given up , or `` dropped '' , half of its potential energy . for both the ball and the electron , the trip down the hill happens spontaneously . the ball and electron move towards a lower energy state all by themselves . on the trip down , there can be things in the way of the ball , like trees or bears to bounce off . for electrons , we can guide electrons using wires and make them flow through electronic components —circuit design— and do interesting things along the way . we can express the voltage between two points mathematically as the change of energy experienced by a charge : $ v = \dfrac { \delta u } { q } $ that 's an intuitive description of voltage in a nutshell . power power is defined as the rate energy ( $ \text u $ ) is transformed or transferred over time . we measure power in units of joules/second , also known as watts . ( $ 1 \ , \text { watt } = 1\ , \text { joule } /\text { second } $ ) $ \text { power } = \dfrac { \text du } { \text dt } $ an electric circuit is capable of transferring power . current is the rate of flow of charge , and voltage measures the energy transferred per unit of charge . we can insert these definitions into the equation for power : $ \text { power } = \dfrac { \text du } { \text dt } = \dfrac { \text du } { \text dq } \cdot \dfrac { \text dq } { \text dt } = v \ , i $ electrical power is the product of voltage times current . in units of watts . summary these mental models for current and voltage will get us started on all sorts of interesting electric circuits . if you want to reach beyond this intuitive description of voltage you can read this more formal mathematical description of electric potential and voltage .
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the positive nuclei in metal atoms are fixed in place and do not contribute to current . even though electrons have a negative charge and do almost all the work in most electric circuits , we still define a positive current as the direction a positive charge would move . this is a very old historical convention .
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and if it does , when the electrons move through an empty wire and arrive back at the positive end of the battery , does it heat up the battery ?
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voltage and current are the cornerstone concepts in electricity . we will create our first mental models for these basic electrical quantities . we will also talk about power , which is what happens when voltage and current act together . charge the concept of electricity arises from an observation of nature . we observe a force between objects , that , like gravity , acts at a distance . the source of this force has been given the name charge . a very noticeable thing about electric force is that it is large , far greater than the force of gravity . unlike gravity , however , there are two types of electric charge . opposite types of charge attract , and like types of charge repel . gravity has only one type : it only attracts , never repels . conductors and insulators conductors are made of atoms whose outer , or valence , electrons have relatively weak bonds to their nuclei , as shown in this fanciful image of a copper atom . when a bunch of metal atoms are together , they gladly share their outer electrons with each other , creating a `` swarm '' of electrons not associated with a particular nucleus . a very small electric force can make the electron swarm move . copper , gold , silver , and aluminum are good conductors . so is saltwater . there are also poor conductors . tungsten—a metal used for light bulb filaments—and carbon—used in graphite form in pencils—are relatively poor conductors because their electrons are less prone to move . insulators are materials whose outer electrons are tightly bound to their nuclei . modest electric forces are not able to pull these electrons free . when an electric force is applied , the electron clouds around the atom stretch and deform in response to the force , but the electrons do not depart . glass , plastic , stone , and air are insulators . even for insulators , though , electric force can always be turned up high enough to rip electrons away—this is called breakdown . that 's what is happening to air molecules when you see a spark . semiconductor materials fall between insulators and conductors . they usually act like insulators , but we can make them act like conductors under certain circumstances . the most well-known semiconductor material is silicon ( atomic number $ 14 $ ) . our ability to finely control the insulating and conducting properties of silicon allows us to create modern marvels like computers and mobile phones . the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current . current is reported as the number of charges per unit time passing through a boundary . visualize placing a boundary all the way through a wire . station yourself near the boundary and count the number of charges passing by . report how much charge passed through the boundary in one second . we assign a positive sign to current corresponding to the direction a positive charge would be moving . since current is the amount of charge passing through a boundary in a fixed amount of time , it can be expressed mathematically using the following equation : $ i = \dfrac { dq } { dt } $ that 's current in a nutshell . a few remarks on current what carries current in metal ? since electrons are free to move about in metals , moving electrons are what makes up the current in metals . the positive nuclei in metal atoms are fixed in place and do not contribute to current . even though electrons have a negative charge and do almost all the work in most electric circuits , we still define a positive current as the direction a positive charge would move . this is a very old historical convention . can current be carried by positive charges ? yes . there are lots of examples . current is carried by both positive and negative charges in saltwater : if we put ordinary table salt in water , it becomes a good conductor . table salt is sodium chloride , nacl . the salt dissolves in water , into free-floating na $ ^+ $ and cl $ ^- $ ions . both ions respond to electric force and move through the saltwater solution , in opposite directions . in this case , the current is composed of moving atoms , both positive and negative ions , not just loose electrons . inside our bodies , electrical currents are moving ions , both positive and negative . the same definition of current works : count the number of charges passing by in a fixed amount of time . what causes current ? charged objects move in response to electric and magnetic forces . these forces come from electric and magnetic fields , which in turn come from the position and motion of other charges . what is the speed of current ? we do n't talk very often about the speed of current . answering the question , `` how fast is the current flowing ? '' requires understanding of a complex physical phenomenon and is not often relevant . current usually is n't about meters per second , it 's about charge per second . more often , we answer the question `` how much current is flowing ? '' all the time . how do we talk about current ? when discussing current , terms like through and in make a lot of sense . current flows through a resistor ; current flows in a wire . if you hear , `` the current across ... '' , it should sound odd . voltage to get our initial toehold on the concept of voltage , let 's look at an analogy : voltage resembles gravity for a mass $ m $ , a change of height $ h $ corresponds to a change in potential energy , $ \delta u = mg\delta h $ . for a charged particle $ q $ , a voltage $ v $ corresponds to a change in potential energy , $ \delta u = qv $ . voltage in an electric circuit is analogous to the product of $ g\cdot \delta h $ . where $ g $ is the acceleration due to gravity and $ \delta h $ is the change of height . a ball at the top of the hill rolls down . when it is halfway down , it has given up half of its potential energy . an electron at the top of a voltage `` hill '' travels `` downhill '' through wires and elements of a circuit . it gives up its potential energy , doing work along the way . when the electron is halfway down the hill , it has given up , or `` dropped '' , half of its potential energy . for both the ball and the electron , the trip down the hill happens spontaneously . the ball and electron move towards a lower energy state all by themselves . on the trip down , there can be things in the way of the ball , like trees or bears to bounce off . for electrons , we can guide electrons using wires and make them flow through electronic components —circuit design— and do interesting things along the way . we can express the voltage between two points mathematically as the change of energy experienced by a charge : $ v = \dfrac { \delta u } { q } $ that 's an intuitive description of voltage in a nutshell . power power is defined as the rate energy ( $ \text u $ ) is transformed or transferred over time . we measure power in units of joules/second , also known as watts . ( $ 1 \ , \text { watt } = 1\ , \text { joule } /\text { second } $ ) $ \text { power } = \dfrac { \text du } { \text dt } $ an electric circuit is capable of transferring power . current is the rate of flow of charge , and voltage measures the energy transferred per unit of charge . we can insert these definitions into the equation for power : $ \text { power } = \dfrac { \text du } { \text dt } = \dfrac { \text du } { \text dq } \cdot \dfrac { \text dq } { \text dt } = v \ , i $ electrical power is the product of voltage times current . in units of watts . summary these mental models for current and voltage will get us started on all sorts of interesting electric circuits . if you want to reach beyond this intuitive description of voltage you can read this more formal mathematical description of electric potential and voltage .
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the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current .
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hey , why electric current is a flow ?
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voltage and current are the cornerstone concepts in electricity . we will create our first mental models for these basic electrical quantities . we will also talk about power , which is what happens when voltage and current act together . charge the concept of electricity arises from an observation of nature . we observe a force between objects , that , like gravity , acts at a distance . the source of this force has been given the name charge . a very noticeable thing about electric force is that it is large , far greater than the force of gravity . unlike gravity , however , there are two types of electric charge . opposite types of charge attract , and like types of charge repel . gravity has only one type : it only attracts , never repels . conductors and insulators conductors are made of atoms whose outer , or valence , electrons have relatively weak bonds to their nuclei , as shown in this fanciful image of a copper atom . when a bunch of metal atoms are together , they gladly share their outer electrons with each other , creating a `` swarm '' of electrons not associated with a particular nucleus . a very small electric force can make the electron swarm move . copper , gold , silver , and aluminum are good conductors . so is saltwater . there are also poor conductors . tungsten—a metal used for light bulb filaments—and carbon—used in graphite form in pencils—are relatively poor conductors because their electrons are less prone to move . insulators are materials whose outer electrons are tightly bound to their nuclei . modest electric forces are not able to pull these electrons free . when an electric force is applied , the electron clouds around the atom stretch and deform in response to the force , but the electrons do not depart . glass , plastic , stone , and air are insulators . even for insulators , though , electric force can always be turned up high enough to rip electrons away—this is called breakdown . that 's what is happening to air molecules when you see a spark . semiconductor materials fall between insulators and conductors . they usually act like insulators , but we can make them act like conductors under certain circumstances . the most well-known semiconductor material is silicon ( atomic number $ 14 $ ) . our ability to finely control the insulating and conducting properties of silicon allows us to create modern marvels like computers and mobile phones . the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current . current is reported as the number of charges per unit time passing through a boundary . visualize placing a boundary all the way through a wire . station yourself near the boundary and count the number of charges passing by . report how much charge passed through the boundary in one second . we assign a positive sign to current corresponding to the direction a positive charge would be moving . since current is the amount of charge passing through a boundary in a fixed amount of time , it can be expressed mathematically using the following equation : $ i = \dfrac { dq } { dt } $ that 's current in a nutshell . a few remarks on current what carries current in metal ? since electrons are free to move about in metals , moving electrons are what makes up the current in metals . the positive nuclei in metal atoms are fixed in place and do not contribute to current . even though electrons have a negative charge and do almost all the work in most electric circuits , we still define a positive current as the direction a positive charge would move . this is a very old historical convention . can current be carried by positive charges ? yes . there are lots of examples . current is carried by both positive and negative charges in saltwater : if we put ordinary table salt in water , it becomes a good conductor . table salt is sodium chloride , nacl . the salt dissolves in water , into free-floating na $ ^+ $ and cl $ ^- $ ions . both ions respond to electric force and move through the saltwater solution , in opposite directions . in this case , the current is composed of moving atoms , both positive and negative ions , not just loose electrons . inside our bodies , electrical currents are moving ions , both positive and negative . the same definition of current works : count the number of charges passing by in a fixed amount of time . what causes current ? charged objects move in response to electric and magnetic forces . these forces come from electric and magnetic fields , which in turn come from the position and motion of other charges . what is the speed of current ? we do n't talk very often about the speed of current . answering the question , `` how fast is the current flowing ? '' requires understanding of a complex physical phenomenon and is not often relevant . current usually is n't about meters per second , it 's about charge per second . more often , we answer the question `` how much current is flowing ? '' all the time . how do we talk about current ? when discussing current , terms like through and in make a lot of sense . current flows through a resistor ; current flows in a wire . if you hear , `` the current across ... '' , it should sound odd . voltage to get our initial toehold on the concept of voltage , let 's look at an analogy : voltage resembles gravity for a mass $ m $ , a change of height $ h $ corresponds to a change in potential energy , $ \delta u = mg\delta h $ . for a charged particle $ q $ , a voltage $ v $ corresponds to a change in potential energy , $ \delta u = qv $ . voltage in an electric circuit is analogous to the product of $ g\cdot \delta h $ . where $ g $ is the acceleration due to gravity and $ \delta h $ is the change of height . a ball at the top of the hill rolls down . when it is halfway down , it has given up half of its potential energy . an electron at the top of a voltage `` hill '' travels `` downhill '' through wires and elements of a circuit . it gives up its potential energy , doing work along the way . when the electron is halfway down the hill , it has given up , or `` dropped '' , half of its potential energy . for both the ball and the electron , the trip down the hill happens spontaneously . the ball and electron move towards a lower energy state all by themselves . on the trip down , there can be things in the way of the ball , like trees or bears to bounce off . for electrons , we can guide electrons using wires and make them flow through electronic components —circuit design— and do interesting things along the way . we can express the voltage between two points mathematically as the change of energy experienced by a charge : $ v = \dfrac { \delta u } { q } $ that 's an intuitive description of voltage in a nutshell . power power is defined as the rate energy ( $ \text u $ ) is transformed or transferred over time . we measure power in units of joules/second , also known as watts . ( $ 1 \ , \text { watt } = 1\ , \text { joule } /\text { second } $ ) $ \text { power } = \dfrac { \text du } { \text dt } $ an electric circuit is capable of transferring power . current is the rate of flow of charge , and voltage measures the energy transferred per unit of charge . we can insert these definitions into the equation for power : $ \text { power } = \dfrac { \text du } { \text dt } = \dfrac { \text du } { \text dq } \cdot \dfrac { \text dq } { \text dt } = v \ , i $ electrical power is the product of voltage times current . in units of watts . summary these mental models for current and voltage will get us started on all sorts of interesting electric circuits . if you want to reach beyond this intuitive description of voltage you can read this more formal mathematical description of electric potential and voltage .
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this is a very old historical convention . can current be carried by positive charges ? yes .
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what is common between fluids and charges ?
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voltage and current are the cornerstone concepts in electricity . we will create our first mental models for these basic electrical quantities . we will also talk about power , which is what happens when voltage and current act together . charge the concept of electricity arises from an observation of nature . we observe a force between objects , that , like gravity , acts at a distance . the source of this force has been given the name charge . a very noticeable thing about electric force is that it is large , far greater than the force of gravity . unlike gravity , however , there are two types of electric charge . opposite types of charge attract , and like types of charge repel . gravity has only one type : it only attracts , never repels . conductors and insulators conductors are made of atoms whose outer , or valence , electrons have relatively weak bonds to their nuclei , as shown in this fanciful image of a copper atom . when a bunch of metal atoms are together , they gladly share their outer electrons with each other , creating a `` swarm '' of electrons not associated with a particular nucleus . a very small electric force can make the electron swarm move . copper , gold , silver , and aluminum are good conductors . so is saltwater . there are also poor conductors . tungsten—a metal used for light bulb filaments—and carbon—used in graphite form in pencils—are relatively poor conductors because their electrons are less prone to move . insulators are materials whose outer electrons are tightly bound to their nuclei . modest electric forces are not able to pull these electrons free . when an electric force is applied , the electron clouds around the atom stretch and deform in response to the force , but the electrons do not depart . glass , plastic , stone , and air are insulators . even for insulators , though , electric force can always be turned up high enough to rip electrons away—this is called breakdown . that 's what is happening to air molecules when you see a spark . semiconductor materials fall between insulators and conductors . they usually act like insulators , but we can make them act like conductors under certain circumstances . the most well-known semiconductor material is silicon ( atomic number $ 14 $ ) . our ability to finely control the insulating and conducting properties of silicon allows us to create modern marvels like computers and mobile phones . the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current . current is reported as the number of charges per unit time passing through a boundary . visualize placing a boundary all the way through a wire . station yourself near the boundary and count the number of charges passing by . report how much charge passed through the boundary in one second . we assign a positive sign to current corresponding to the direction a positive charge would be moving . since current is the amount of charge passing through a boundary in a fixed amount of time , it can be expressed mathematically using the following equation : $ i = \dfrac { dq } { dt } $ that 's current in a nutshell . a few remarks on current what carries current in metal ? since electrons are free to move about in metals , moving electrons are what makes up the current in metals . the positive nuclei in metal atoms are fixed in place and do not contribute to current . even though electrons have a negative charge and do almost all the work in most electric circuits , we still define a positive current as the direction a positive charge would move . this is a very old historical convention . can current be carried by positive charges ? yes . there are lots of examples . current is carried by both positive and negative charges in saltwater : if we put ordinary table salt in water , it becomes a good conductor . table salt is sodium chloride , nacl . the salt dissolves in water , into free-floating na $ ^+ $ and cl $ ^- $ ions . both ions respond to electric force and move through the saltwater solution , in opposite directions . in this case , the current is composed of moving atoms , both positive and negative ions , not just loose electrons . inside our bodies , electrical currents are moving ions , both positive and negative . the same definition of current works : count the number of charges passing by in a fixed amount of time . what causes current ? charged objects move in response to electric and magnetic forces . these forces come from electric and magnetic fields , which in turn come from the position and motion of other charges . what is the speed of current ? we do n't talk very often about the speed of current . answering the question , `` how fast is the current flowing ? '' requires understanding of a complex physical phenomenon and is not often relevant . current usually is n't about meters per second , it 's about charge per second . more often , we answer the question `` how much current is flowing ? '' all the time . how do we talk about current ? when discussing current , terms like through and in make a lot of sense . current flows through a resistor ; current flows in a wire . if you hear , `` the current across ... '' , it should sound odd . voltage to get our initial toehold on the concept of voltage , let 's look at an analogy : voltage resembles gravity for a mass $ m $ , a change of height $ h $ corresponds to a change in potential energy , $ \delta u = mg\delta h $ . for a charged particle $ q $ , a voltage $ v $ corresponds to a change in potential energy , $ \delta u = qv $ . voltage in an electric circuit is analogous to the product of $ g\cdot \delta h $ . where $ g $ is the acceleration due to gravity and $ \delta h $ is the change of height . a ball at the top of the hill rolls down . when it is halfway down , it has given up half of its potential energy . an electron at the top of a voltage `` hill '' travels `` downhill '' through wires and elements of a circuit . it gives up its potential energy , doing work along the way . when the electron is halfway down the hill , it has given up , or `` dropped '' , half of its potential energy . for both the ball and the electron , the trip down the hill happens spontaneously . the ball and electron move towards a lower energy state all by themselves . on the trip down , there can be things in the way of the ball , like trees or bears to bounce off . for electrons , we can guide electrons using wires and make them flow through electronic components —circuit design— and do interesting things along the way . we can express the voltage between two points mathematically as the change of energy experienced by a charge : $ v = \dfrac { \delta u } { q } $ that 's an intuitive description of voltage in a nutshell . power power is defined as the rate energy ( $ \text u $ ) is transformed or transferred over time . we measure power in units of joules/second , also known as watts . ( $ 1 \ , \text { watt } = 1\ , \text { joule } /\text { second } $ ) $ \text { power } = \dfrac { \text du } { \text dt } $ an electric circuit is capable of transferring power . current is the rate of flow of charge , and voltage measures the energy transferred per unit of charge . we can insert these definitions into the equation for power : $ \text { power } = \dfrac { \text du } { \text dt } = \dfrac { \text du } { \text dq } \cdot \dfrac { \text dq } { \text dt } = v \ , i $ electrical power is the product of voltage times current . in units of watts . summary these mental models for current and voltage will get us started on all sorts of interesting electric circuits . if you want to reach beyond this intuitive description of voltage you can read this more formal mathematical description of electric potential and voltage .
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if you hear , `` the current across ... '' , it should sound odd . voltage to get our initial toehold on the concept of voltage , let 's look at an analogy : voltage resembles gravity for a mass $ m $ , a change of height $ h $ corresponds to a change in potential energy , $ \delta u = mg\delta h $ . for a charged particle $ q $ , a voltage $ v $ corresponds to a change in potential energy , $ \delta u = qv $ .
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what is the actual meaning of voltage ?
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voltage and current are the cornerstone concepts in electricity . we will create our first mental models for these basic electrical quantities . we will also talk about power , which is what happens when voltage and current act together . charge the concept of electricity arises from an observation of nature . we observe a force between objects , that , like gravity , acts at a distance . the source of this force has been given the name charge . a very noticeable thing about electric force is that it is large , far greater than the force of gravity . unlike gravity , however , there are two types of electric charge . opposite types of charge attract , and like types of charge repel . gravity has only one type : it only attracts , never repels . conductors and insulators conductors are made of atoms whose outer , or valence , electrons have relatively weak bonds to their nuclei , as shown in this fanciful image of a copper atom . when a bunch of metal atoms are together , they gladly share their outer electrons with each other , creating a `` swarm '' of electrons not associated with a particular nucleus . a very small electric force can make the electron swarm move . copper , gold , silver , and aluminum are good conductors . so is saltwater . there are also poor conductors . tungsten—a metal used for light bulb filaments—and carbon—used in graphite form in pencils—are relatively poor conductors because their electrons are less prone to move . insulators are materials whose outer electrons are tightly bound to their nuclei . modest electric forces are not able to pull these electrons free . when an electric force is applied , the electron clouds around the atom stretch and deform in response to the force , but the electrons do not depart . glass , plastic , stone , and air are insulators . even for insulators , though , electric force can always be turned up high enough to rip electrons away—this is called breakdown . that 's what is happening to air molecules when you see a spark . semiconductor materials fall between insulators and conductors . they usually act like insulators , but we can make them act like conductors under certain circumstances . the most well-known semiconductor material is silicon ( atomic number $ 14 $ ) . our ability to finely control the insulating and conducting properties of silicon allows us to create modern marvels like computers and mobile phones . the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current . current is reported as the number of charges per unit time passing through a boundary . visualize placing a boundary all the way through a wire . station yourself near the boundary and count the number of charges passing by . report how much charge passed through the boundary in one second . we assign a positive sign to current corresponding to the direction a positive charge would be moving . since current is the amount of charge passing through a boundary in a fixed amount of time , it can be expressed mathematically using the following equation : $ i = \dfrac { dq } { dt } $ that 's current in a nutshell . a few remarks on current what carries current in metal ? since electrons are free to move about in metals , moving electrons are what makes up the current in metals . the positive nuclei in metal atoms are fixed in place and do not contribute to current . even though electrons have a negative charge and do almost all the work in most electric circuits , we still define a positive current as the direction a positive charge would move . this is a very old historical convention . can current be carried by positive charges ? yes . there are lots of examples . current is carried by both positive and negative charges in saltwater : if we put ordinary table salt in water , it becomes a good conductor . table salt is sodium chloride , nacl . the salt dissolves in water , into free-floating na $ ^+ $ and cl $ ^- $ ions . both ions respond to electric force and move through the saltwater solution , in opposite directions . in this case , the current is composed of moving atoms , both positive and negative ions , not just loose electrons . inside our bodies , electrical currents are moving ions , both positive and negative . the same definition of current works : count the number of charges passing by in a fixed amount of time . what causes current ? charged objects move in response to electric and magnetic forces . these forces come from electric and magnetic fields , which in turn come from the position and motion of other charges . what is the speed of current ? we do n't talk very often about the speed of current . answering the question , `` how fast is the current flowing ? '' requires understanding of a complex physical phenomenon and is not often relevant . current usually is n't about meters per second , it 's about charge per second . more often , we answer the question `` how much current is flowing ? '' all the time . how do we talk about current ? when discussing current , terms like through and in make a lot of sense . current flows through a resistor ; current flows in a wire . if you hear , `` the current across ... '' , it should sound odd . voltage to get our initial toehold on the concept of voltage , let 's look at an analogy : voltage resembles gravity for a mass $ m $ , a change of height $ h $ corresponds to a change in potential energy , $ \delta u = mg\delta h $ . for a charged particle $ q $ , a voltage $ v $ corresponds to a change in potential energy , $ \delta u = qv $ . voltage in an electric circuit is analogous to the product of $ g\cdot \delta h $ . where $ g $ is the acceleration due to gravity and $ \delta h $ is the change of height . a ball at the top of the hill rolls down . when it is halfway down , it has given up half of its potential energy . an electron at the top of a voltage `` hill '' travels `` downhill '' through wires and elements of a circuit . it gives up its potential energy , doing work along the way . when the electron is halfway down the hill , it has given up , or `` dropped '' , half of its potential energy . for both the ball and the electron , the trip down the hill happens spontaneously . the ball and electron move towards a lower energy state all by themselves . on the trip down , there can be things in the way of the ball , like trees or bears to bounce off . for electrons , we can guide electrons using wires and make them flow through electronic components —circuit design— and do interesting things along the way . we can express the voltage between two points mathematically as the change of energy experienced by a charge : $ v = \dfrac { \delta u } { q } $ that 's an intuitive description of voltage in a nutshell . power power is defined as the rate energy ( $ \text u $ ) is transformed or transferred over time . we measure power in units of joules/second , also known as watts . ( $ 1 \ , \text { watt } = 1\ , \text { joule } /\text { second } $ ) $ \text { power } = \dfrac { \text du } { \text dt } $ an electric circuit is capable of transferring power . current is the rate of flow of charge , and voltage measures the energy transferred per unit of charge . we can insert these definitions into the equation for power : $ \text { power } = \dfrac { \text du } { \text dt } = \dfrac { \text du } { \text dq } \cdot \dfrac { \text dq } { \text dt } = v \ , i $ electrical power is the product of voltage times current . in units of watts . summary these mental models for current and voltage will get us started on all sorts of interesting electric circuits . if you want to reach beyond this intuitive description of voltage you can read this more formal mathematical description of electric potential and voltage .
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semiconductor materials fall between insulators and conductors . they usually act like insulators , but we can make them act like conductors under certain circumstances . the most well-known semiconductor material is silicon ( atomic number $ 14 $ ) .
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can certain currents actually stop at a certain length ?
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voltage and current are the cornerstone concepts in electricity . we will create our first mental models for these basic electrical quantities . we will also talk about power , which is what happens when voltage and current act together . charge the concept of electricity arises from an observation of nature . we observe a force between objects , that , like gravity , acts at a distance . the source of this force has been given the name charge . a very noticeable thing about electric force is that it is large , far greater than the force of gravity . unlike gravity , however , there are two types of electric charge . opposite types of charge attract , and like types of charge repel . gravity has only one type : it only attracts , never repels . conductors and insulators conductors are made of atoms whose outer , or valence , electrons have relatively weak bonds to their nuclei , as shown in this fanciful image of a copper atom . when a bunch of metal atoms are together , they gladly share their outer electrons with each other , creating a `` swarm '' of electrons not associated with a particular nucleus . a very small electric force can make the electron swarm move . copper , gold , silver , and aluminum are good conductors . so is saltwater . there are also poor conductors . tungsten—a metal used for light bulb filaments—and carbon—used in graphite form in pencils—are relatively poor conductors because their electrons are less prone to move . insulators are materials whose outer electrons are tightly bound to their nuclei . modest electric forces are not able to pull these electrons free . when an electric force is applied , the electron clouds around the atom stretch and deform in response to the force , but the electrons do not depart . glass , plastic , stone , and air are insulators . even for insulators , though , electric force can always be turned up high enough to rip electrons away—this is called breakdown . that 's what is happening to air molecules when you see a spark . semiconductor materials fall between insulators and conductors . they usually act like insulators , but we can make them act like conductors under certain circumstances . the most well-known semiconductor material is silicon ( atomic number $ 14 $ ) . our ability to finely control the insulating and conducting properties of silicon allows us to create modern marvels like computers and mobile phones . the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current . current is reported as the number of charges per unit time passing through a boundary . visualize placing a boundary all the way through a wire . station yourself near the boundary and count the number of charges passing by . report how much charge passed through the boundary in one second . we assign a positive sign to current corresponding to the direction a positive charge would be moving . since current is the amount of charge passing through a boundary in a fixed amount of time , it can be expressed mathematically using the following equation : $ i = \dfrac { dq } { dt } $ that 's current in a nutshell . a few remarks on current what carries current in metal ? since electrons are free to move about in metals , moving electrons are what makes up the current in metals . the positive nuclei in metal atoms are fixed in place and do not contribute to current . even though electrons have a negative charge and do almost all the work in most electric circuits , we still define a positive current as the direction a positive charge would move . this is a very old historical convention . can current be carried by positive charges ? yes . there are lots of examples . current is carried by both positive and negative charges in saltwater : if we put ordinary table salt in water , it becomes a good conductor . table salt is sodium chloride , nacl . the salt dissolves in water , into free-floating na $ ^+ $ and cl $ ^- $ ions . both ions respond to electric force and move through the saltwater solution , in opposite directions . in this case , the current is composed of moving atoms , both positive and negative ions , not just loose electrons . inside our bodies , electrical currents are moving ions , both positive and negative . the same definition of current works : count the number of charges passing by in a fixed amount of time . what causes current ? charged objects move in response to electric and magnetic forces . these forces come from electric and magnetic fields , which in turn come from the position and motion of other charges . what is the speed of current ? we do n't talk very often about the speed of current . answering the question , `` how fast is the current flowing ? '' requires understanding of a complex physical phenomenon and is not often relevant . current usually is n't about meters per second , it 's about charge per second . more often , we answer the question `` how much current is flowing ? '' all the time . how do we talk about current ? when discussing current , terms like through and in make a lot of sense . current flows through a resistor ; current flows in a wire . if you hear , `` the current across ... '' , it should sound odd . voltage to get our initial toehold on the concept of voltage , let 's look at an analogy : voltage resembles gravity for a mass $ m $ , a change of height $ h $ corresponds to a change in potential energy , $ \delta u = mg\delta h $ . for a charged particle $ q $ , a voltage $ v $ corresponds to a change in potential energy , $ \delta u = qv $ . voltage in an electric circuit is analogous to the product of $ g\cdot \delta h $ . where $ g $ is the acceleration due to gravity and $ \delta h $ is the change of height . a ball at the top of the hill rolls down . when it is halfway down , it has given up half of its potential energy . an electron at the top of a voltage `` hill '' travels `` downhill '' through wires and elements of a circuit . it gives up its potential energy , doing work along the way . when the electron is halfway down the hill , it has given up , or `` dropped '' , half of its potential energy . for both the ball and the electron , the trip down the hill happens spontaneously . the ball and electron move towards a lower energy state all by themselves . on the trip down , there can be things in the way of the ball , like trees or bears to bounce off . for electrons , we can guide electrons using wires and make them flow through electronic components —circuit design— and do interesting things along the way . we can express the voltage between two points mathematically as the change of energy experienced by a charge : $ v = \dfrac { \delta u } { q } $ that 's an intuitive description of voltage in a nutshell . power power is defined as the rate energy ( $ \text u $ ) is transformed or transferred over time . we measure power in units of joules/second , also known as watts . ( $ 1 \ , \text { watt } = 1\ , \text { joule } /\text { second } $ ) $ \text { power } = \dfrac { \text du } { \text dt } $ an electric circuit is capable of transferring power . current is the rate of flow of charge , and voltage measures the energy transferred per unit of charge . we can insert these definitions into the equation for power : $ \text { power } = \dfrac { \text du } { \text dt } = \dfrac { \text du } { \text dq } \cdot \dfrac { \text dq } { \text dt } = v \ , i $ electrical power is the product of voltage times current . in units of watts . summary these mental models for current and voltage will get us started on all sorts of interesting electric circuits . if you want to reach beyond this intuitive description of voltage you can read this more formal mathematical description of electric potential and voltage .
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insulators are materials whose outer electrons are tightly bound to their nuclei . modest electric forces are not able to pull these electrons free . when an electric force is applied , the electron clouds around the atom stretch and deform in response to the force , but the electrons do not depart .
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i read somewhere that ionosphere has a high concentration of ions and free electrons.so what will happen if a man somehow is dropped in that region and is stuck ?
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voltage and current are the cornerstone concepts in electricity . we will create our first mental models for these basic electrical quantities . we will also talk about power , which is what happens when voltage and current act together . charge the concept of electricity arises from an observation of nature . we observe a force between objects , that , like gravity , acts at a distance . the source of this force has been given the name charge . a very noticeable thing about electric force is that it is large , far greater than the force of gravity . unlike gravity , however , there are two types of electric charge . opposite types of charge attract , and like types of charge repel . gravity has only one type : it only attracts , never repels . conductors and insulators conductors are made of atoms whose outer , or valence , electrons have relatively weak bonds to their nuclei , as shown in this fanciful image of a copper atom . when a bunch of metal atoms are together , they gladly share their outer electrons with each other , creating a `` swarm '' of electrons not associated with a particular nucleus . a very small electric force can make the electron swarm move . copper , gold , silver , and aluminum are good conductors . so is saltwater . there are also poor conductors . tungsten—a metal used for light bulb filaments—and carbon—used in graphite form in pencils—are relatively poor conductors because their electrons are less prone to move . insulators are materials whose outer electrons are tightly bound to their nuclei . modest electric forces are not able to pull these electrons free . when an electric force is applied , the electron clouds around the atom stretch and deform in response to the force , but the electrons do not depart . glass , plastic , stone , and air are insulators . even for insulators , though , electric force can always be turned up high enough to rip electrons away—this is called breakdown . that 's what is happening to air molecules when you see a spark . semiconductor materials fall between insulators and conductors . they usually act like insulators , but we can make them act like conductors under certain circumstances . the most well-known semiconductor material is silicon ( atomic number $ 14 $ ) . our ability to finely control the insulating and conducting properties of silicon allows us to create modern marvels like computers and mobile phones . the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current . current is reported as the number of charges per unit time passing through a boundary . visualize placing a boundary all the way through a wire . station yourself near the boundary and count the number of charges passing by . report how much charge passed through the boundary in one second . we assign a positive sign to current corresponding to the direction a positive charge would be moving . since current is the amount of charge passing through a boundary in a fixed amount of time , it can be expressed mathematically using the following equation : $ i = \dfrac { dq } { dt } $ that 's current in a nutshell . a few remarks on current what carries current in metal ? since electrons are free to move about in metals , moving electrons are what makes up the current in metals . the positive nuclei in metal atoms are fixed in place and do not contribute to current . even though electrons have a negative charge and do almost all the work in most electric circuits , we still define a positive current as the direction a positive charge would move . this is a very old historical convention . can current be carried by positive charges ? yes . there are lots of examples . current is carried by both positive and negative charges in saltwater : if we put ordinary table salt in water , it becomes a good conductor . table salt is sodium chloride , nacl . the salt dissolves in water , into free-floating na $ ^+ $ and cl $ ^- $ ions . both ions respond to electric force and move through the saltwater solution , in opposite directions . in this case , the current is composed of moving atoms , both positive and negative ions , not just loose electrons . inside our bodies , electrical currents are moving ions , both positive and negative . the same definition of current works : count the number of charges passing by in a fixed amount of time . what causes current ? charged objects move in response to electric and magnetic forces . these forces come from electric and magnetic fields , which in turn come from the position and motion of other charges . what is the speed of current ? we do n't talk very often about the speed of current . answering the question , `` how fast is the current flowing ? '' requires understanding of a complex physical phenomenon and is not often relevant . current usually is n't about meters per second , it 's about charge per second . more often , we answer the question `` how much current is flowing ? '' all the time . how do we talk about current ? when discussing current , terms like through and in make a lot of sense . current flows through a resistor ; current flows in a wire . if you hear , `` the current across ... '' , it should sound odd . voltage to get our initial toehold on the concept of voltage , let 's look at an analogy : voltage resembles gravity for a mass $ m $ , a change of height $ h $ corresponds to a change in potential energy , $ \delta u = mg\delta h $ . for a charged particle $ q $ , a voltage $ v $ corresponds to a change in potential energy , $ \delta u = qv $ . voltage in an electric circuit is analogous to the product of $ g\cdot \delta h $ . where $ g $ is the acceleration due to gravity and $ \delta h $ is the change of height . a ball at the top of the hill rolls down . when it is halfway down , it has given up half of its potential energy . an electron at the top of a voltage `` hill '' travels `` downhill '' through wires and elements of a circuit . it gives up its potential energy , doing work along the way . when the electron is halfway down the hill , it has given up , or `` dropped '' , half of its potential energy . for both the ball and the electron , the trip down the hill happens spontaneously . the ball and electron move towards a lower energy state all by themselves . on the trip down , there can be things in the way of the ball , like trees or bears to bounce off . for electrons , we can guide electrons using wires and make them flow through electronic components —circuit design— and do interesting things along the way . we can express the voltage between two points mathematically as the change of energy experienced by a charge : $ v = \dfrac { \delta u } { q } $ that 's an intuitive description of voltage in a nutshell . power power is defined as the rate energy ( $ \text u $ ) is transformed or transferred over time . we measure power in units of joules/second , also known as watts . ( $ 1 \ , \text { watt } = 1\ , \text { joule } /\text { second } $ ) $ \text { power } = \dfrac { \text du } { \text dt } $ an electric circuit is capable of transferring power . current is the rate of flow of charge , and voltage measures the energy transferred per unit of charge . we can insert these definitions into the equation for power : $ \text { power } = \dfrac { \text du } { \text dt } = \dfrac { \text du } { \text dq } \cdot \dfrac { \text dq } { \text dt } = v \ , i $ electrical power is the product of voltage times current . in units of watts . summary these mental models for current and voltage will get us started on all sorts of interesting electric circuits . if you want to reach beyond this intuitive description of voltage you can read this more formal mathematical description of electric potential and voltage .
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if you hear , `` the current across ... '' , it should sound odd . voltage to get our initial toehold on the concept of voltage , let 's look at an analogy : voltage resembles gravity for a mass $ m $ , a change of height $ h $ corresponds to a change in potential energy , $ \delta u = mg\delta h $ . for a charged particle $ q $ , a voltage $ v $ corresponds to a change in potential energy , $ \delta u = qv $ .
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how much voltage can a computer have ?
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voltage and current are the cornerstone concepts in electricity . we will create our first mental models for these basic electrical quantities . we will also talk about power , which is what happens when voltage and current act together . charge the concept of electricity arises from an observation of nature . we observe a force between objects , that , like gravity , acts at a distance . the source of this force has been given the name charge . a very noticeable thing about electric force is that it is large , far greater than the force of gravity . unlike gravity , however , there are two types of electric charge . opposite types of charge attract , and like types of charge repel . gravity has only one type : it only attracts , never repels . conductors and insulators conductors are made of atoms whose outer , or valence , electrons have relatively weak bonds to their nuclei , as shown in this fanciful image of a copper atom . when a bunch of metal atoms are together , they gladly share their outer electrons with each other , creating a `` swarm '' of electrons not associated with a particular nucleus . a very small electric force can make the electron swarm move . copper , gold , silver , and aluminum are good conductors . so is saltwater . there are also poor conductors . tungsten—a metal used for light bulb filaments—and carbon—used in graphite form in pencils—are relatively poor conductors because their electrons are less prone to move . insulators are materials whose outer electrons are tightly bound to their nuclei . modest electric forces are not able to pull these electrons free . when an electric force is applied , the electron clouds around the atom stretch and deform in response to the force , but the electrons do not depart . glass , plastic , stone , and air are insulators . even for insulators , though , electric force can always be turned up high enough to rip electrons away—this is called breakdown . that 's what is happening to air molecules when you see a spark . semiconductor materials fall between insulators and conductors . they usually act like insulators , but we can make them act like conductors under certain circumstances . the most well-known semiconductor material is silicon ( atomic number $ 14 $ ) . our ability to finely control the insulating and conducting properties of silicon allows us to create modern marvels like computers and mobile phones . the details of semiconductor operation are governed by our understanding of quantum mechanics . current current is the flow of charge . charge flows in a current . current is reported as the number of charges per unit time passing through a boundary . visualize placing a boundary all the way through a wire . station yourself near the boundary and count the number of charges passing by . report how much charge passed through the boundary in one second . we assign a positive sign to current corresponding to the direction a positive charge would be moving . since current is the amount of charge passing through a boundary in a fixed amount of time , it can be expressed mathematically using the following equation : $ i = \dfrac { dq } { dt } $ that 's current in a nutshell . a few remarks on current what carries current in metal ? since electrons are free to move about in metals , moving electrons are what makes up the current in metals . the positive nuclei in metal atoms are fixed in place and do not contribute to current . even though electrons have a negative charge and do almost all the work in most electric circuits , we still define a positive current as the direction a positive charge would move . this is a very old historical convention . can current be carried by positive charges ? yes . there are lots of examples . current is carried by both positive and negative charges in saltwater : if we put ordinary table salt in water , it becomes a good conductor . table salt is sodium chloride , nacl . the salt dissolves in water , into free-floating na $ ^+ $ and cl $ ^- $ ions . both ions respond to electric force and move through the saltwater solution , in opposite directions . in this case , the current is composed of moving atoms , both positive and negative ions , not just loose electrons . inside our bodies , electrical currents are moving ions , both positive and negative . the same definition of current works : count the number of charges passing by in a fixed amount of time . what causes current ? charged objects move in response to electric and magnetic forces . these forces come from electric and magnetic fields , which in turn come from the position and motion of other charges . what is the speed of current ? we do n't talk very often about the speed of current . answering the question , `` how fast is the current flowing ? '' requires understanding of a complex physical phenomenon and is not often relevant . current usually is n't about meters per second , it 's about charge per second . more often , we answer the question `` how much current is flowing ? '' all the time . how do we talk about current ? when discussing current , terms like through and in make a lot of sense . current flows through a resistor ; current flows in a wire . if you hear , `` the current across ... '' , it should sound odd . voltage to get our initial toehold on the concept of voltage , let 's look at an analogy : voltage resembles gravity for a mass $ m $ , a change of height $ h $ corresponds to a change in potential energy , $ \delta u = mg\delta h $ . for a charged particle $ q $ , a voltage $ v $ corresponds to a change in potential energy , $ \delta u = qv $ . voltage in an electric circuit is analogous to the product of $ g\cdot \delta h $ . where $ g $ is the acceleration due to gravity and $ \delta h $ is the change of height . a ball at the top of the hill rolls down . when it is halfway down , it has given up half of its potential energy . an electron at the top of a voltage `` hill '' travels `` downhill '' through wires and elements of a circuit . it gives up its potential energy , doing work along the way . when the electron is halfway down the hill , it has given up , or `` dropped '' , half of its potential energy . for both the ball and the electron , the trip down the hill happens spontaneously . the ball and electron move towards a lower energy state all by themselves . on the trip down , there can be things in the way of the ball , like trees or bears to bounce off . for electrons , we can guide electrons using wires and make them flow through electronic components —circuit design— and do interesting things along the way . we can express the voltage between two points mathematically as the change of energy experienced by a charge : $ v = \dfrac { \delta u } { q } $ that 's an intuitive description of voltage in a nutshell . power power is defined as the rate energy ( $ \text u $ ) is transformed or transferred over time . we measure power in units of joules/second , also known as watts . ( $ 1 \ , \text { watt } = 1\ , \text { joule } /\text { second } $ ) $ \text { power } = \dfrac { \text du } { \text dt } $ an electric circuit is capable of transferring power . current is the rate of flow of charge , and voltage measures the energy transferred per unit of charge . we can insert these definitions into the equation for power : $ \text { power } = \dfrac { \text du } { \text dt } = \dfrac { \text du } { \text dq } \cdot \dfrac { \text dq } { \text dt } = v \ , i $ electrical power is the product of voltage times current . in units of watts . summary these mental models for current and voltage will get us started on all sorts of interesting electric circuits . if you want to reach beyond this intuitive description of voltage you can read this more formal mathematical description of electric potential and voltage .
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voltage and current are the cornerstone concepts in electricity . we will create our first mental models for these basic electrical quantities .
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so if a car is electricity , then its speed is current , fuel is voltage and friction is resistance ?
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in david 's neo-classical era , still life was considered the least important subject type . only minor artists bothered with what was then seen as the most purely decorative and trivial of painting subjects . the hierarchy of subjects went roughly from the most important—historical and religious themes ( often very large in scale ) ; to important—portraiture ( usually of moderate scale ) ; less important—landscape & amp ; genre ( themes of common life , usually of modest scale ) ; to least important— still life ( generally small canvases ) . a hopeless subject there had been one significant historical exception . in the 17th century in northern europe and particularly in the netherlands , still life blossomed . but this period was brief and had little impact in france other than in the work of chardin . so why would cézanne turn so often to this discredited subject ? it was the very fact that still life was so neglected that seems to have attracted cézanne to it . so outmoded was the iconography ( symbolic forms and references ) in still life that this rather hopeless subject was freed of virtually all convention . here was a subject that offered extraordinary freedom , a blank slate that gave cézanne the opportunity to invent meaning unfettered by tradition . and cézanne would almost single-handedly revive the subject of still life making it an important subject for picasso , matisse , and others in the 20th century . the image at the top of this page looks simple enough , a wine bottle , a basket tipped up to expose a bounty of fruit inside , a plate of what are perhaps stacked cookies or small rolls , and a tablecloth both gathered and draped . nothing remarkable , at least not until one begins to notice the odd errors in drawing . look , for instance , at the lines that represent the close and far edge of the table . i remember an old student of mine remarking to the class , `` i would never hire him as a carpenter ! '' what she had noticed was the odd stepping of a line that we expect to be straight . purposeful errors but that is not all that is wrong . the table seems to be too steeply tipped at the left , so much so that the fruit is in danger of rolling off it . the bottle looks tipsy and the cookies are very odd indeed . the cookies stacked below the top layer seem as if they are viewed from the side , but at the same moment , the two on top seem to pop upward as if we were looking down at them . this is an important key to understanding the questions that we 've raised about cézanne 's pictures so far . like edouard manet , from whom he borrowed so much , cézanne was prompted to rethink the value of the various illusionistic techniques that he had inherited from the masters of the renaissance and baroque eras . this was due in part to the growing impact of photography and its transformation of modern representation . while degas and monet borrowed from the camera the fragmenting of time , cézanne saw this mechanized segmentation of time as artificial and at odds with the perception of the human eye . by cézanne 's era , the camera did shatter time into fragments as do non-digital cameras that can be set so that the shutter is open to light for only 1/1000 of a second . sight and memory cézanne pushed this distinction between the vision of the camera and of human vision . he reasoned that the same issues applied to the illusionism of the old masters , of raphael , leonardo , caravaggio , etc . for instance , think about how linear perspective works . since the early renaissance , constructing the illusion of space required that the artist remain frozen in a single point in space in order maintain consistent recession among all receding orthogonals . this frozen vantage point belongs to both the artist and then the viewer . but is it a full description of the the experience of human sight ? cézanne 's still life suggests that it is not . if a renaissance painter set out to render cézanne 's still life objects ( not that they would , mind you ) , that artist would have placed himself in a specific point before the table and taken great pains to render the collection of tabletop objects only from that original perspective . every orthogonal line would remain consistent ( and straight ) . but this is clearly not what cézanne had in mind . his perspective seems jumbled . when we first look carefully , it may appear as if he was simply unable to draw , but if you spend more time , it may occur to you that cézanne is , in fact , drawing carefully , although according to a new set of rules . seemingly simple , cézanne 's concern with representing the true experience of sight had enormous implications for 20th century visual culture . cézanne realized that unlike the fairly simple and static renaissance vision of space , people actually see in a fashion that is more complex , we see through both time and space . in other words , we move as we see . in contemporary terms , one might say that human vision is less like the frozen vision of a still camera and more akin to the continuous vision of a video camera except that he worked with oil on canvas which dries and becomes static . purposeful destruction so very tentatively , cézanne began the purposeful destruction of the unified image . look again at the cookies , or whatever they are , stacked upon the plate in the upper right . is it possible that the gentle disagreements that we noted result from the representation of two slightly different view points ? these are not large ruptures , but rather , they suggest careful and tentative discovery . it is as if cézanne had simply depicted the bottom cookies as he looked across at them and then as he looked more slightly down at the top cookies after shifting his weight to his forward leg . furthermore , i 'm not sure that he was all that proud of these breaks that allow for more than a single perspective . look , for instance , at the points where the table must break to express these multiple perspectives and you will notice that they are each hidden from view . nevertheless , in doing this , cézanne changed the direction of painting . essay by dr. beth harris and dr. steven zucker additional resources : this painting at the art institute of chicago still life tour from the national gallery of art selection on the basket of apples from richard brettell , post-impressionists . chicago ( 1987 , p. 67
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but is it a full description of the the experience of human sight ? cézanne 's still life suggests that it is not . if a renaissance painter set out to render cézanne 's still life objects ( not that they would , mind you ) , that artist would have placed himself in a specific point before the table and taken great pains to render the collection of tabletop objects only from that original perspective .
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how life - like is the scene ?
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key points : dna cloning is a molecular biology technique that makes many identical copies of a piece of dna , such as a gene . in a typical cloning experiment , a target gene is inserted into a circular piece of dna called a plasmid . the plasmid is introduced into bacteria via process called transformation , and bacteria carrying the plasmid are selected using antibiotics . bacteria with the correct plasmid are used to make more plasmid dna or , in some cases , induced to express the gene and make protein . introduction when you hear the word “ cloning , ” you may think of the cloning of whole organisms , such as dolly the sheep . however , all it means to clone something is to make a genetically exact copy of it . in a molecular biology lab , what ’ s most often cloned is a gene or other small piece of dna . if your friend the molecular biologist say that her “ cloning ” isn ’ t working , she 's almost certainly talking about copying bits of dna , not making the next dolly ! overview of dna cloning dna cloning is the process of making multiple , identical copies of a particular piece of dna . in a typical dna cloning procedure , the gene or other dna fragment of interest ( perhaps a gene for a medically important human protein ) is first inserted into a circular piece of dna called a plasmid . the insertion is done using enzymes that “ cut and paste ” dna , and it produces a molecule of recombinant dna , or dna assembled out of fragments from multiple sources . next , the recombinant plasmid is introduced into bacteria . bacteria carrying the plasmid are selected and grown up . as they reproduce , they replicate the plasmid and pass it on to their offspring , making copies of the dna it contains . what is the point of making many copies of a dna sequence in a plasmid ? in some cases , we need lots of dna copies to conduct experiments or build new plasmids . in other cases , the piece of dna encodes a useful protein , and the bacteria are used as “ factories ” to make the protein . for instance , the human insulin gene is expressed in e. coli bacteria to make insulin used by diabetics . steps of dna cloning dna cloning is used for many purposes . as an example , let 's see how dna cloning can be used to synthesize a protein ( such as human insulin ) in bacteria . the basic steps are : cut open the plasmid and `` paste '' in the gene . this process relies on restriction enzymes ( which cut dna ) and dna ligase ( which joins dna ) . transform the plasmid into bacteria . use antibiotic selection to identify the bacteria that took up the plasmid . grow up lots of plasmid-carrying bacteria and use them as `` factories '' to make the protein . harvest the protein from the bacteria and purify it . let 's take a closer look at each step . 1 . cutting and pasting dna how can pieces of dna from different sources be joined together ? a common method uses two types of enzymes : restriction enzymes and dna ligase . a restriction enzyme is a dna-cutting enzyme that recognizes a specific target sequence and cuts dna into two pieces at or near that site . many restriction enzymes produce cut ends with short , single-stranded overhangs . if two molecules have matching overhangs , they can base-pair and stick together . however , they wo n't combine to form an unbroken dna molecule until they are joined by dna ligase , which seals gaps in the dna backbone . our goal in cloning is to insert a target gene ( e.g. , for human insulin ) into a plasmid . using a carefully chosen restriction enzyme , we digest : the plasmid , which has a single cut site the target gene fragment , which has a cut site near each end then , we combine the fragments with dna ligase , which links them to make a recombinant plasmid containing the gene . 2 . bacterial transformation and selection plasmids and other dna can be introduced into bacteria , such as the harmless e. coli used in labs , in a process called transformation . during transformation , specially prepared bacterial cells are given a shock ( such as high temperature ) that encourages them to take up foreign dna . a plasmid typically contains an antibiotic resistance gene , which allows bacteria to survive in the presence of a specific antibiotic . thus , bacteria that took up the plasmid can be selected on nutrient plates containing the antibiotic . bacteria without a plasmid will die , while bacteria carrying a plasmid can live and reproduce . each surviving bacterium will give rise to a small , dot-like group , or colony , of identical bacteria that all carry the same plasmid . not all colonies will necessarily contain the right plasmid . that ’ s because , during a ligation , dna fragments don ’ t always get “ pasted ” in exactly the way we intend . instead , we must collect dna from several colonies and see whether each one contain the right plasmid . methods like restriction enzyme digestion and pcr are commonly used to check the plasmids . 3 . protein production once we have found a bacterial colony with the right plasmid , we can grow a large culture of plasmid-bearing bacteria . then , we give the bacteria a chemical signal that instructs them to make the target protein . the bacteria serve as miniature “ factories , '' churning out large amounts of protein . for instance , if our plasmid contained the human insulin gene , the bacteria would start transcribing the gene and translating the mrna to produce many molecules of human insulin protein . once the protein has been produced , the bacterial cells can be split open to release it . there are many other proteins and macromolecules floating around in bacteria besides the target protein ( e.g. , insulin ) . because of this , the target protein must be purified , or separated from the other contents of the cells by biochemical techniques . the purified protein can be used for experiments or , in the case of insulin , administered to patients . uses of dna cloning dna molecules built through cloning techniques are used for many purposes in molecular biology . a short list of examples includes : biopharmaceuticals . dna cloning can be used to make human proteins with biomedical applications , such as the insulin mentioned above . other examples of recombinant proteins include human growth hormone , which is given to patients who are unable to synthesize the hormone , and tissue plasminogen activator ( tpa ) , which is used to treat strokes and prevent blood clots . recombinant proteins like these are often made in bacteria . gene therapy . in some genetic disorders , patients lack the functional form of a particular gene . gene therapy attempts to provide a normal copy of the gene to the cells of a patient ’ s body . for example , dna cloning was used to build plasmids containing a normal version of the gene that 's nonfunctional in cystic fibrosis . when the plasmids were delivered to the lungs of cystic fibrosis patients , lung function deteriorated less quickly $ ^2 $ . gene analysis . in basic research labs , biologists often use dna cloning to build artificial , recombinant versions of genes that help them understand how normal genes in an organism function . these are just a few examples of how dna cloning is used in biology today . dna cloning is a very common technique that is used in a huge variety of molecular biology applications .
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in a typical cloning experiment , a target gene is inserted into a circular piece of dna called a plasmid . the plasmid is introduced into bacteria via process called transformation , and bacteria carrying the plasmid are selected using antibiotics . bacteria with the correct plasmid are used to make more plasmid dna or , in some cases , induced to express the gene and make protein .
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do the bacteria ever make mistakes in the replication process ?
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key points : dna cloning is a molecular biology technique that makes many identical copies of a piece of dna , such as a gene . in a typical cloning experiment , a target gene is inserted into a circular piece of dna called a plasmid . the plasmid is introduced into bacteria via process called transformation , and bacteria carrying the plasmid are selected using antibiotics . bacteria with the correct plasmid are used to make more plasmid dna or , in some cases , induced to express the gene and make protein . introduction when you hear the word “ cloning , ” you may think of the cloning of whole organisms , such as dolly the sheep . however , all it means to clone something is to make a genetically exact copy of it . in a molecular biology lab , what ’ s most often cloned is a gene or other small piece of dna . if your friend the molecular biologist say that her “ cloning ” isn ’ t working , she 's almost certainly talking about copying bits of dna , not making the next dolly ! overview of dna cloning dna cloning is the process of making multiple , identical copies of a particular piece of dna . in a typical dna cloning procedure , the gene or other dna fragment of interest ( perhaps a gene for a medically important human protein ) is first inserted into a circular piece of dna called a plasmid . the insertion is done using enzymes that “ cut and paste ” dna , and it produces a molecule of recombinant dna , or dna assembled out of fragments from multiple sources . next , the recombinant plasmid is introduced into bacteria . bacteria carrying the plasmid are selected and grown up . as they reproduce , they replicate the plasmid and pass it on to their offspring , making copies of the dna it contains . what is the point of making many copies of a dna sequence in a plasmid ? in some cases , we need lots of dna copies to conduct experiments or build new plasmids . in other cases , the piece of dna encodes a useful protein , and the bacteria are used as “ factories ” to make the protein . for instance , the human insulin gene is expressed in e. coli bacteria to make insulin used by diabetics . steps of dna cloning dna cloning is used for many purposes . as an example , let 's see how dna cloning can be used to synthesize a protein ( such as human insulin ) in bacteria . the basic steps are : cut open the plasmid and `` paste '' in the gene . this process relies on restriction enzymes ( which cut dna ) and dna ligase ( which joins dna ) . transform the plasmid into bacteria . use antibiotic selection to identify the bacteria that took up the plasmid . grow up lots of plasmid-carrying bacteria and use them as `` factories '' to make the protein . harvest the protein from the bacteria and purify it . let 's take a closer look at each step . 1 . cutting and pasting dna how can pieces of dna from different sources be joined together ? a common method uses two types of enzymes : restriction enzymes and dna ligase . a restriction enzyme is a dna-cutting enzyme that recognizes a specific target sequence and cuts dna into two pieces at or near that site . many restriction enzymes produce cut ends with short , single-stranded overhangs . if two molecules have matching overhangs , they can base-pair and stick together . however , they wo n't combine to form an unbroken dna molecule until they are joined by dna ligase , which seals gaps in the dna backbone . our goal in cloning is to insert a target gene ( e.g. , for human insulin ) into a plasmid . using a carefully chosen restriction enzyme , we digest : the plasmid , which has a single cut site the target gene fragment , which has a cut site near each end then , we combine the fragments with dna ligase , which links them to make a recombinant plasmid containing the gene . 2 . bacterial transformation and selection plasmids and other dna can be introduced into bacteria , such as the harmless e. coli used in labs , in a process called transformation . during transformation , specially prepared bacterial cells are given a shock ( such as high temperature ) that encourages them to take up foreign dna . a plasmid typically contains an antibiotic resistance gene , which allows bacteria to survive in the presence of a specific antibiotic . thus , bacteria that took up the plasmid can be selected on nutrient plates containing the antibiotic . bacteria without a plasmid will die , while bacteria carrying a plasmid can live and reproduce . each surviving bacterium will give rise to a small , dot-like group , or colony , of identical bacteria that all carry the same plasmid . not all colonies will necessarily contain the right plasmid . that ’ s because , during a ligation , dna fragments don ’ t always get “ pasted ” in exactly the way we intend . instead , we must collect dna from several colonies and see whether each one contain the right plasmid . methods like restriction enzyme digestion and pcr are commonly used to check the plasmids . 3 . protein production once we have found a bacterial colony with the right plasmid , we can grow a large culture of plasmid-bearing bacteria . then , we give the bacteria a chemical signal that instructs them to make the target protein . the bacteria serve as miniature “ factories , '' churning out large amounts of protein . for instance , if our plasmid contained the human insulin gene , the bacteria would start transcribing the gene and translating the mrna to produce many molecules of human insulin protein . once the protein has been produced , the bacterial cells can be split open to release it . there are many other proteins and macromolecules floating around in bacteria besides the target protein ( e.g. , insulin ) . because of this , the target protein must be purified , or separated from the other contents of the cells by biochemical techniques . the purified protein can be used for experiments or , in the case of insulin , administered to patients . uses of dna cloning dna molecules built through cloning techniques are used for many purposes in molecular biology . a short list of examples includes : biopharmaceuticals . dna cloning can be used to make human proteins with biomedical applications , such as the insulin mentioned above . other examples of recombinant proteins include human growth hormone , which is given to patients who are unable to synthesize the hormone , and tissue plasminogen activator ( tpa ) , which is used to treat strokes and prevent blood clots . recombinant proteins like these are often made in bacteria . gene therapy . in some genetic disorders , patients lack the functional form of a particular gene . gene therapy attempts to provide a normal copy of the gene to the cells of a patient ’ s body . for example , dna cloning was used to build plasmids containing a normal version of the gene that 's nonfunctional in cystic fibrosis . when the plasmids were delivered to the lungs of cystic fibrosis patients , lung function deteriorated less quickly $ ^2 $ . gene analysis . in basic research labs , biologists often use dna cloning to build artificial , recombinant versions of genes that help them understand how normal genes in an organism function . these are just a few examples of how dna cloning is used in biology today . dna cloning is a very common technique that is used in a huge variety of molecular biology applications .
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methods like restriction enzyme digestion and pcr are commonly used to check the plasmids . 3 . protein production once we have found a bacterial colony with the right plasmid , we can grow a large culture of plasmid-bearing bacteria .
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in section 3 on protein production it says humans and bacteria share the same genetic code ... how on earth is that possible ?
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key points : dna cloning is a molecular biology technique that makes many identical copies of a piece of dna , such as a gene . in a typical cloning experiment , a target gene is inserted into a circular piece of dna called a plasmid . the plasmid is introduced into bacteria via process called transformation , and bacteria carrying the plasmid are selected using antibiotics . bacteria with the correct plasmid are used to make more plasmid dna or , in some cases , induced to express the gene and make protein . introduction when you hear the word “ cloning , ” you may think of the cloning of whole organisms , such as dolly the sheep . however , all it means to clone something is to make a genetically exact copy of it . in a molecular biology lab , what ’ s most often cloned is a gene or other small piece of dna . if your friend the molecular biologist say that her “ cloning ” isn ’ t working , she 's almost certainly talking about copying bits of dna , not making the next dolly ! overview of dna cloning dna cloning is the process of making multiple , identical copies of a particular piece of dna . in a typical dna cloning procedure , the gene or other dna fragment of interest ( perhaps a gene for a medically important human protein ) is first inserted into a circular piece of dna called a plasmid . the insertion is done using enzymes that “ cut and paste ” dna , and it produces a molecule of recombinant dna , or dna assembled out of fragments from multiple sources . next , the recombinant plasmid is introduced into bacteria . bacteria carrying the plasmid are selected and grown up . as they reproduce , they replicate the plasmid and pass it on to their offspring , making copies of the dna it contains . what is the point of making many copies of a dna sequence in a plasmid ? in some cases , we need lots of dna copies to conduct experiments or build new plasmids . in other cases , the piece of dna encodes a useful protein , and the bacteria are used as “ factories ” to make the protein . for instance , the human insulin gene is expressed in e. coli bacteria to make insulin used by diabetics . steps of dna cloning dna cloning is used for many purposes . as an example , let 's see how dna cloning can be used to synthesize a protein ( such as human insulin ) in bacteria . the basic steps are : cut open the plasmid and `` paste '' in the gene . this process relies on restriction enzymes ( which cut dna ) and dna ligase ( which joins dna ) . transform the plasmid into bacteria . use antibiotic selection to identify the bacteria that took up the plasmid . grow up lots of plasmid-carrying bacteria and use them as `` factories '' to make the protein . harvest the protein from the bacteria and purify it . let 's take a closer look at each step . 1 . cutting and pasting dna how can pieces of dna from different sources be joined together ? a common method uses two types of enzymes : restriction enzymes and dna ligase . a restriction enzyme is a dna-cutting enzyme that recognizes a specific target sequence and cuts dna into two pieces at or near that site . many restriction enzymes produce cut ends with short , single-stranded overhangs . if two molecules have matching overhangs , they can base-pair and stick together . however , they wo n't combine to form an unbroken dna molecule until they are joined by dna ligase , which seals gaps in the dna backbone . our goal in cloning is to insert a target gene ( e.g. , for human insulin ) into a plasmid . using a carefully chosen restriction enzyme , we digest : the plasmid , which has a single cut site the target gene fragment , which has a cut site near each end then , we combine the fragments with dna ligase , which links them to make a recombinant plasmid containing the gene . 2 . bacterial transformation and selection plasmids and other dna can be introduced into bacteria , such as the harmless e. coli used in labs , in a process called transformation . during transformation , specially prepared bacterial cells are given a shock ( such as high temperature ) that encourages them to take up foreign dna . a plasmid typically contains an antibiotic resistance gene , which allows bacteria to survive in the presence of a specific antibiotic . thus , bacteria that took up the plasmid can be selected on nutrient plates containing the antibiotic . bacteria without a plasmid will die , while bacteria carrying a plasmid can live and reproduce . each surviving bacterium will give rise to a small , dot-like group , or colony , of identical bacteria that all carry the same plasmid . not all colonies will necessarily contain the right plasmid . that ’ s because , during a ligation , dna fragments don ’ t always get “ pasted ” in exactly the way we intend . instead , we must collect dna from several colonies and see whether each one contain the right plasmid . methods like restriction enzyme digestion and pcr are commonly used to check the plasmids . 3 . protein production once we have found a bacterial colony with the right plasmid , we can grow a large culture of plasmid-bearing bacteria . then , we give the bacteria a chemical signal that instructs them to make the target protein . the bacteria serve as miniature “ factories , '' churning out large amounts of protein . for instance , if our plasmid contained the human insulin gene , the bacteria would start transcribing the gene and translating the mrna to produce many molecules of human insulin protein . once the protein has been produced , the bacterial cells can be split open to release it . there are many other proteins and macromolecules floating around in bacteria besides the target protein ( e.g. , insulin ) . because of this , the target protein must be purified , or separated from the other contents of the cells by biochemical techniques . the purified protein can be used for experiments or , in the case of insulin , administered to patients . uses of dna cloning dna molecules built through cloning techniques are used for many purposes in molecular biology . a short list of examples includes : biopharmaceuticals . dna cloning can be used to make human proteins with biomedical applications , such as the insulin mentioned above . other examples of recombinant proteins include human growth hormone , which is given to patients who are unable to synthesize the hormone , and tissue plasminogen activator ( tpa ) , which is used to treat strokes and prevent blood clots . recombinant proteins like these are often made in bacteria . gene therapy . in some genetic disorders , patients lack the functional form of a particular gene . gene therapy attempts to provide a normal copy of the gene to the cells of a patient ’ s body . for example , dna cloning was used to build plasmids containing a normal version of the gene that 's nonfunctional in cystic fibrosis . when the plasmids were delivered to the lungs of cystic fibrosis patients , lung function deteriorated less quickly $ ^2 $ . gene analysis . in basic research labs , biologists often use dna cloning to build artificial , recombinant versions of genes that help them understand how normal genes in an organism function . these are just a few examples of how dna cloning is used in biology today . dna cloning is a very common technique that is used in a huge variety of molecular biology applications .
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gene therapy . in some genetic disorders , patients lack the functional form of a particular gene . gene therapy attempts to provide a normal copy of the gene to the cells of a patient ’ s body .
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and do we share that genetic code with other organisms as well ?
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key points : dna cloning is a molecular biology technique that makes many identical copies of a piece of dna , such as a gene . in a typical cloning experiment , a target gene is inserted into a circular piece of dna called a plasmid . the plasmid is introduced into bacteria via process called transformation , and bacteria carrying the plasmid are selected using antibiotics . bacteria with the correct plasmid are used to make more plasmid dna or , in some cases , induced to express the gene and make protein . introduction when you hear the word “ cloning , ” you may think of the cloning of whole organisms , such as dolly the sheep . however , all it means to clone something is to make a genetically exact copy of it . in a molecular biology lab , what ’ s most often cloned is a gene or other small piece of dna . if your friend the molecular biologist say that her “ cloning ” isn ’ t working , she 's almost certainly talking about copying bits of dna , not making the next dolly ! overview of dna cloning dna cloning is the process of making multiple , identical copies of a particular piece of dna . in a typical dna cloning procedure , the gene or other dna fragment of interest ( perhaps a gene for a medically important human protein ) is first inserted into a circular piece of dna called a plasmid . the insertion is done using enzymes that “ cut and paste ” dna , and it produces a molecule of recombinant dna , or dna assembled out of fragments from multiple sources . next , the recombinant plasmid is introduced into bacteria . bacteria carrying the plasmid are selected and grown up . as they reproduce , they replicate the plasmid and pass it on to their offspring , making copies of the dna it contains . what is the point of making many copies of a dna sequence in a plasmid ? in some cases , we need lots of dna copies to conduct experiments or build new plasmids . in other cases , the piece of dna encodes a useful protein , and the bacteria are used as “ factories ” to make the protein . for instance , the human insulin gene is expressed in e. coli bacteria to make insulin used by diabetics . steps of dna cloning dna cloning is used for many purposes . as an example , let 's see how dna cloning can be used to synthesize a protein ( such as human insulin ) in bacteria . the basic steps are : cut open the plasmid and `` paste '' in the gene . this process relies on restriction enzymes ( which cut dna ) and dna ligase ( which joins dna ) . transform the plasmid into bacteria . use antibiotic selection to identify the bacteria that took up the plasmid . grow up lots of plasmid-carrying bacteria and use them as `` factories '' to make the protein . harvest the protein from the bacteria and purify it . let 's take a closer look at each step . 1 . cutting and pasting dna how can pieces of dna from different sources be joined together ? a common method uses two types of enzymes : restriction enzymes and dna ligase . a restriction enzyme is a dna-cutting enzyme that recognizes a specific target sequence and cuts dna into two pieces at or near that site . many restriction enzymes produce cut ends with short , single-stranded overhangs . if two molecules have matching overhangs , they can base-pair and stick together . however , they wo n't combine to form an unbroken dna molecule until they are joined by dna ligase , which seals gaps in the dna backbone . our goal in cloning is to insert a target gene ( e.g. , for human insulin ) into a plasmid . using a carefully chosen restriction enzyme , we digest : the plasmid , which has a single cut site the target gene fragment , which has a cut site near each end then , we combine the fragments with dna ligase , which links them to make a recombinant plasmid containing the gene . 2 . bacterial transformation and selection plasmids and other dna can be introduced into bacteria , such as the harmless e. coli used in labs , in a process called transformation . during transformation , specially prepared bacterial cells are given a shock ( such as high temperature ) that encourages them to take up foreign dna . a plasmid typically contains an antibiotic resistance gene , which allows bacteria to survive in the presence of a specific antibiotic . thus , bacteria that took up the plasmid can be selected on nutrient plates containing the antibiotic . bacteria without a plasmid will die , while bacteria carrying a plasmid can live and reproduce . each surviving bacterium will give rise to a small , dot-like group , or colony , of identical bacteria that all carry the same plasmid . not all colonies will necessarily contain the right plasmid . that ’ s because , during a ligation , dna fragments don ’ t always get “ pasted ” in exactly the way we intend . instead , we must collect dna from several colonies and see whether each one contain the right plasmid . methods like restriction enzyme digestion and pcr are commonly used to check the plasmids . 3 . protein production once we have found a bacterial colony with the right plasmid , we can grow a large culture of plasmid-bearing bacteria . then , we give the bacteria a chemical signal that instructs them to make the target protein . the bacteria serve as miniature “ factories , '' churning out large amounts of protein . for instance , if our plasmid contained the human insulin gene , the bacteria would start transcribing the gene and translating the mrna to produce many molecules of human insulin protein . once the protein has been produced , the bacterial cells can be split open to release it . there are many other proteins and macromolecules floating around in bacteria besides the target protein ( e.g. , insulin ) . because of this , the target protein must be purified , or separated from the other contents of the cells by biochemical techniques . the purified protein can be used for experiments or , in the case of insulin , administered to patients . uses of dna cloning dna molecules built through cloning techniques are used for many purposes in molecular biology . a short list of examples includes : biopharmaceuticals . dna cloning can be used to make human proteins with biomedical applications , such as the insulin mentioned above . other examples of recombinant proteins include human growth hormone , which is given to patients who are unable to synthesize the hormone , and tissue plasminogen activator ( tpa ) , which is used to treat strokes and prevent blood clots . recombinant proteins like these are often made in bacteria . gene therapy . in some genetic disorders , patients lack the functional form of a particular gene . gene therapy attempts to provide a normal copy of the gene to the cells of a patient ’ s body . for example , dna cloning was used to build plasmids containing a normal version of the gene that 's nonfunctional in cystic fibrosis . when the plasmids were delivered to the lungs of cystic fibrosis patients , lung function deteriorated less quickly $ ^2 $ . gene analysis . in basic research labs , biologists often use dna cloning to build artificial , recombinant versions of genes that help them understand how normal genes in an organism function . these are just a few examples of how dna cloning is used in biology today . dna cloning is a very common technique that is used in a huge variety of molecular biology applications .
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bacteria without a plasmid will die , while bacteria carrying a plasmid can live and reproduce . each surviving bacterium will give rise to a small , dot-like group , or colony , of identical bacteria that all carry the same plasmid . not all colonies will necessarily contain the right plasmid .
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are identical twins also clones ?
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key points : dna cloning is a molecular biology technique that makes many identical copies of a piece of dna , such as a gene . in a typical cloning experiment , a target gene is inserted into a circular piece of dna called a plasmid . the plasmid is introduced into bacteria via process called transformation , and bacteria carrying the plasmid are selected using antibiotics . bacteria with the correct plasmid are used to make more plasmid dna or , in some cases , induced to express the gene and make protein . introduction when you hear the word “ cloning , ” you may think of the cloning of whole organisms , such as dolly the sheep . however , all it means to clone something is to make a genetically exact copy of it . in a molecular biology lab , what ’ s most often cloned is a gene or other small piece of dna . if your friend the molecular biologist say that her “ cloning ” isn ’ t working , she 's almost certainly talking about copying bits of dna , not making the next dolly ! overview of dna cloning dna cloning is the process of making multiple , identical copies of a particular piece of dna . in a typical dna cloning procedure , the gene or other dna fragment of interest ( perhaps a gene for a medically important human protein ) is first inserted into a circular piece of dna called a plasmid . the insertion is done using enzymes that “ cut and paste ” dna , and it produces a molecule of recombinant dna , or dna assembled out of fragments from multiple sources . next , the recombinant plasmid is introduced into bacteria . bacteria carrying the plasmid are selected and grown up . as they reproduce , they replicate the plasmid and pass it on to their offspring , making copies of the dna it contains . what is the point of making many copies of a dna sequence in a plasmid ? in some cases , we need lots of dna copies to conduct experiments or build new plasmids . in other cases , the piece of dna encodes a useful protein , and the bacteria are used as “ factories ” to make the protein . for instance , the human insulin gene is expressed in e. coli bacteria to make insulin used by diabetics . steps of dna cloning dna cloning is used for many purposes . as an example , let 's see how dna cloning can be used to synthesize a protein ( such as human insulin ) in bacteria . the basic steps are : cut open the plasmid and `` paste '' in the gene . this process relies on restriction enzymes ( which cut dna ) and dna ligase ( which joins dna ) . transform the plasmid into bacteria . use antibiotic selection to identify the bacteria that took up the plasmid . grow up lots of plasmid-carrying bacteria and use them as `` factories '' to make the protein . harvest the protein from the bacteria and purify it . let 's take a closer look at each step . 1 . cutting and pasting dna how can pieces of dna from different sources be joined together ? a common method uses two types of enzymes : restriction enzymes and dna ligase . a restriction enzyme is a dna-cutting enzyme that recognizes a specific target sequence and cuts dna into two pieces at or near that site . many restriction enzymes produce cut ends with short , single-stranded overhangs . if two molecules have matching overhangs , they can base-pair and stick together . however , they wo n't combine to form an unbroken dna molecule until they are joined by dna ligase , which seals gaps in the dna backbone . our goal in cloning is to insert a target gene ( e.g. , for human insulin ) into a plasmid . using a carefully chosen restriction enzyme , we digest : the plasmid , which has a single cut site the target gene fragment , which has a cut site near each end then , we combine the fragments with dna ligase , which links them to make a recombinant plasmid containing the gene . 2 . bacterial transformation and selection plasmids and other dna can be introduced into bacteria , such as the harmless e. coli used in labs , in a process called transformation . during transformation , specially prepared bacterial cells are given a shock ( such as high temperature ) that encourages them to take up foreign dna . a plasmid typically contains an antibiotic resistance gene , which allows bacteria to survive in the presence of a specific antibiotic . thus , bacteria that took up the plasmid can be selected on nutrient plates containing the antibiotic . bacteria without a plasmid will die , while bacteria carrying a plasmid can live and reproduce . each surviving bacterium will give rise to a small , dot-like group , or colony , of identical bacteria that all carry the same plasmid . not all colonies will necessarily contain the right plasmid . that ’ s because , during a ligation , dna fragments don ’ t always get “ pasted ” in exactly the way we intend . instead , we must collect dna from several colonies and see whether each one contain the right plasmid . methods like restriction enzyme digestion and pcr are commonly used to check the plasmids . 3 . protein production once we have found a bacterial colony with the right plasmid , we can grow a large culture of plasmid-bearing bacteria . then , we give the bacteria a chemical signal that instructs them to make the target protein . the bacteria serve as miniature “ factories , '' churning out large amounts of protein . for instance , if our plasmid contained the human insulin gene , the bacteria would start transcribing the gene and translating the mrna to produce many molecules of human insulin protein . once the protein has been produced , the bacterial cells can be split open to release it . there are many other proteins and macromolecules floating around in bacteria besides the target protein ( e.g. , insulin ) . because of this , the target protein must be purified , or separated from the other contents of the cells by biochemical techniques . the purified protein can be used for experiments or , in the case of insulin , administered to patients . uses of dna cloning dna molecules built through cloning techniques are used for many purposes in molecular biology . a short list of examples includes : biopharmaceuticals . dna cloning can be used to make human proteins with biomedical applications , such as the insulin mentioned above . other examples of recombinant proteins include human growth hormone , which is given to patients who are unable to synthesize the hormone , and tissue plasminogen activator ( tpa ) , which is used to treat strokes and prevent blood clots . recombinant proteins like these are often made in bacteria . gene therapy . in some genetic disorders , patients lack the functional form of a particular gene . gene therapy attempts to provide a normal copy of the gene to the cells of a patient ’ s body . for example , dna cloning was used to build plasmids containing a normal version of the gene that 's nonfunctional in cystic fibrosis . when the plasmids were delivered to the lungs of cystic fibrosis patients , lung function deteriorated less quickly $ ^2 $ . gene analysis . in basic research labs , biologists often use dna cloning to build artificial , recombinant versions of genes that help them understand how normal genes in an organism function . these are just a few examples of how dna cloning is used in biology today . dna cloning is a very common technique that is used in a huge variety of molecular biology applications .
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key points : dna cloning is a molecular biology technique that makes many identical copies of a piece of dna , such as a gene . in a typical cloning experiment , a target gene is inserted into a circular piece of dna called a plasmid .
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what is meant by totipotency and pleuripotency ?
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key points : dna cloning is a molecular biology technique that makes many identical copies of a piece of dna , such as a gene . in a typical cloning experiment , a target gene is inserted into a circular piece of dna called a plasmid . the plasmid is introduced into bacteria via process called transformation , and bacteria carrying the plasmid are selected using antibiotics . bacteria with the correct plasmid are used to make more plasmid dna or , in some cases , induced to express the gene and make protein . introduction when you hear the word “ cloning , ” you may think of the cloning of whole organisms , such as dolly the sheep . however , all it means to clone something is to make a genetically exact copy of it . in a molecular biology lab , what ’ s most often cloned is a gene or other small piece of dna . if your friend the molecular biologist say that her “ cloning ” isn ’ t working , she 's almost certainly talking about copying bits of dna , not making the next dolly ! overview of dna cloning dna cloning is the process of making multiple , identical copies of a particular piece of dna . in a typical dna cloning procedure , the gene or other dna fragment of interest ( perhaps a gene for a medically important human protein ) is first inserted into a circular piece of dna called a plasmid . the insertion is done using enzymes that “ cut and paste ” dna , and it produces a molecule of recombinant dna , or dna assembled out of fragments from multiple sources . next , the recombinant plasmid is introduced into bacteria . bacteria carrying the plasmid are selected and grown up . as they reproduce , they replicate the plasmid and pass it on to their offspring , making copies of the dna it contains . what is the point of making many copies of a dna sequence in a plasmid ? in some cases , we need lots of dna copies to conduct experiments or build new plasmids . in other cases , the piece of dna encodes a useful protein , and the bacteria are used as “ factories ” to make the protein . for instance , the human insulin gene is expressed in e. coli bacteria to make insulin used by diabetics . steps of dna cloning dna cloning is used for many purposes . as an example , let 's see how dna cloning can be used to synthesize a protein ( such as human insulin ) in bacteria . the basic steps are : cut open the plasmid and `` paste '' in the gene . this process relies on restriction enzymes ( which cut dna ) and dna ligase ( which joins dna ) . transform the plasmid into bacteria . use antibiotic selection to identify the bacteria that took up the plasmid . grow up lots of plasmid-carrying bacteria and use them as `` factories '' to make the protein . harvest the protein from the bacteria and purify it . let 's take a closer look at each step . 1 . cutting and pasting dna how can pieces of dna from different sources be joined together ? a common method uses two types of enzymes : restriction enzymes and dna ligase . a restriction enzyme is a dna-cutting enzyme that recognizes a specific target sequence and cuts dna into two pieces at or near that site . many restriction enzymes produce cut ends with short , single-stranded overhangs . if two molecules have matching overhangs , they can base-pair and stick together . however , they wo n't combine to form an unbroken dna molecule until they are joined by dna ligase , which seals gaps in the dna backbone . our goal in cloning is to insert a target gene ( e.g. , for human insulin ) into a plasmid . using a carefully chosen restriction enzyme , we digest : the plasmid , which has a single cut site the target gene fragment , which has a cut site near each end then , we combine the fragments with dna ligase , which links them to make a recombinant plasmid containing the gene . 2 . bacterial transformation and selection plasmids and other dna can be introduced into bacteria , such as the harmless e. coli used in labs , in a process called transformation . during transformation , specially prepared bacterial cells are given a shock ( such as high temperature ) that encourages them to take up foreign dna . a plasmid typically contains an antibiotic resistance gene , which allows bacteria to survive in the presence of a specific antibiotic . thus , bacteria that took up the plasmid can be selected on nutrient plates containing the antibiotic . bacteria without a plasmid will die , while bacteria carrying a plasmid can live and reproduce . each surviving bacterium will give rise to a small , dot-like group , or colony , of identical bacteria that all carry the same plasmid . not all colonies will necessarily contain the right plasmid . that ’ s because , during a ligation , dna fragments don ’ t always get “ pasted ” in exactly the way we intend . instead , we must collect dna from several colonies and see whether each one contain the right plasmid . methods like restriction enzyme digestion and pcr are commonly used to check the plasmids . 3 . protein production once we have found a bacterial colony with the right plasmid , we can grow a large culture of plasmid-bearing bacteria . then , we give the bacteria a chemical signal that instructs them to make the target protein . the bacteria serve as miniature “ factories , '' churning out large amounts of protein . for instance , if our plasmid contained the human insulin gene , the bacteria would start transcribing the gene and translating the mrna to produce many molecules of human insulin protein . once the protein has been produced , the bacterial cells can be split open to release it . there are many other proteins and macromolecules floating around in bacteria besides the target protein ( e.g. , insulin ) . because of this , the target protein must be purified , or separated from the other contents of the cells by biochemical techniques . the purified protein can be used for experiments or , in the case of insulin , administered to patients . uses of dna cloning dna molecules built through cloning techniques are used for many purposes in molecular biology . a short list of examples includes : biopharmaceuticals . dna cloning can be used to make human proteins with biomedical applications , such as the insulin mentioned above . other examples of recombinant proteins include human growth hormone , which is given to patients who are unable to synthesize the hormone , and tissue plasminogen activator ( tpa ) , which is used to treat strokes and prevent blood clots . recombinant proteins like these are often made in bacteria . gene therapy . in some genetic disorders , patients lack the functional form of a particular gene . gene therapy attempts to provide a normal copy of the gene to the cells of a patient ’ s body . for example , dna cloning was used to build plasmids containing a normal version of the gene that 's nonfunctional in cystic fibrosis . when the plasmids were delivered to the lungs of cystic fibrosis patients , lung function deteriorated less quickly $ ^2 $ . gene analysis . in basic research labs , biologists often use dna cloning to build artificial , recombinant versions of genes that help them understand how normal genes in an organism function . these are just a few examples of how dna cloning is used in biology today . dna cloning is a very common technique that is used in a huge variety of molecular biology applications .
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instead , we must collect dna from several colonies and see whether each one contain the right plasmid . methods like restriction enzyme digestion and pcr are commonly used to check the plasmids . 3 .
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why plasmids can replicate independantly of the chromosomes ?
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key points : dna cloning is a molecular biology technique that makes many identical copies of a piece of dna , such as a gene . in a typical cloning experiment , a target gene is inserted into a circular piece of dna called a plasmid . the plasmid is introduced into bacteria via process called transformation , and bacteria carrying the plasmid are selected using antibiotics . bacteria with the correct plasmid are used to make more plasmid dna or , in some cases , induced to express the gene and make protein . introduction when you hear the word “ cloning , ” you may think of the cloning of whole organisms , such as dolly the sheep . however , all it means to clone something is to make a genetically exact copy of it . in a molecular biology lab , what ’ s most often cloned is a gene or other small piece of dna . if your friend the molecular biologist say that her “ cloning ” isn ’ t working , she 's almost certainly talking about copying bits of dna , not making the next dolly ! overview of dna cloning dna cloning is the process of making multiple , identical copies of a particular piece of dna . in a typical dna cloning procedure , the gene or other dna fragment of interest ( perhaps a gene for a medically important human protein ) is first inserted into a circular piece of dna called a plasmid . the insertion is done using enzymes that “ cut and paste ” dna , and it produces a molecule of recombinant dna , or dna assembled out of fragments from multiple sources . next , the recombinant plasmid is introduced into bacteria . bacteria carrying the plasmid are selected and grown up . as they reproduce , they replicate the plasmid and pass it on to their offspring , making copies of the dna it contains . what is the point of making many copies of a dna sequence in a plasmid ? in some cases , we need lots of dna copies to conduct experiments or build new plasmids . in other cases , the piece of dna encodes a useful protein , and the bacteria are used as “ factories ” to make the protein . for instance , the human insulin gene is expressed in e. coli bacteria to make insulin used by diabetics . steps of dna cloning dna cloning is used for many purposes . as an example , let 's see how dna cloning can be used to synthesize a protein ( such as human insulin ) in bacteria . the basic steps are : cut open the plasmid and `` paste '' in the gene . this process relies on restriction enzymes ( which cut dna ) and dna ligase ( which joins dna ) . transform the plasmid into bacteria . use antibiotic selection to identify the bacteria that took up the plasmid . grow up lots of plasmid-carrying bacteria and use them as `` factories '' to make the protein . harvest the protein from the bacteria and purify it . let 's take a closer look at each step . 1 . cutting and pasting dna how can pieces of dna from different sources be joined together ? a common method uses two types of enzymes : restriction enzymes and dna ligase . a restriction enzyme is a dna-cutting enzyme that recognizes a specific target sequence and cuts dna into two pieces at or near that site . many restriction enzymes produce cut ends with short , single-stranded overhangs . if two molecules have matching overhangs , they can base-pair and stick together . however , they wo n't combine to form an unbroken dna molecule until they are joined by dna ligase , which seals gaps in the dna backbone . our goal in cloning is to insert a target gene ( e.g. , for human insulin ) into a plasmid . using a carefully chosen restriction enzyme , we digest : the plasmid , which has a single cut site the target gene fragment , which has a cut site near each end then , we combine the fragments with dna ligase , which links them to make a recombinant plasmid containing the gene . 2 . bacterial transformation and selection plasmids and other dna can be introduced into bacteria , such as the harmless e. coli used in labs , in a process called transformation . during transformation , specially prepared bacterial cells are given a shock ( such as high temperature ) that encourages them to take up foreign dna . a plasmid typically contains an antibiotic resistance gene , which allows bacteria to survive in the presence of a specific antibiotic . thus , bacteria that took up the plasmid can be selected on nutrient plates containing the antibiotic . bacteria without a plasmid will die , while bacteria carrying a plasmid can live and reproduce . each surviving bacterium will give rise to a small , dot-like group , or colony , of identical bacteria that all carry the same plasmid . not all colonies will necessarily contain the right plasmid . that ’ s because , during a ligation , dna fragments don ’ t always get “ pasted ” in exactly the way we intend . instead , we must collect dna from several colonies and see whether each one contain the right plasmid . methods like restriction enzyme digestion and pcr are commonly used to check the plasmids . 3 . protein production once we have found a bacterial colony with the right plasmid , we can grow a large culture of plasmid-bearing bacteria . then , we give the bacteria a chemical signal that instructs them to make the target protein . the bacteria serve as miniature “ factories , '' churning out large amounts of protein . for instance , if our plasmid contained the human insulin gene , the bacteria would start transcribing the gene and translating the mrna to produce many molecules of human insulin protein . once the protein has been produced , the bacterial cells can be split open to release it . there are many other proteins and macromolecules floating around in bacteria besides the target protein ( e.g. , insulin ) . because of this , the target protein must be purified , or separated from the other contents of the cells by biochemical techniques . the purified protein can be used for experiments or , in the case of insulin , administered to patients . uses of dna cloning dna molecules built through cloning techniques are used for many purposes in molecular biology . a short list of examples includes : biopharmaceuticals . dna cloning can be used to make human proteins with biomedical applications , such as the insulin mentioned above . other examples of recombinant proteins include human growth hormone , which is given to patients who are unable to synthesize the hormone , and tissue plasminogen activator ( tpa ) , which is used to treat strokes and prevent blood clots . recombinant proteins like these are often made in bacteria . gene therapy . in some genetic disorders , patients lack the functional form of a particular gene . gene therapy attempts to provide a normal copy of the gene to the cells of a patient ’ s body . for example , dna cloning was used to build plasmids containing a normal version of the gene that 's nonfunctional in cystic fibrosis . when the plasmids were delivered to the lungs of cystic fibrosis patients , lung function deteriorated less quickly $ ^2 $ . gene analysis . in basic research labs , biologists often use dna cloning to build artificial , recombinant versions of genes that help them understand how normal genes in an organism function . these are just a few examples of how dna cloning is used in biology today . dna cloning is a very common technique that is used in a huge variety of molecular biology applications .
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during transformation , specially prepared bacterial cells are given a shock ( such as high temperature ) that encourages them to take up foreign dna . a plasmid typically contains an antibiotic resistance gene , which allows bacteria to survive in the presence of a specific antibiotic . thus , bacteria that took up the plasmid can be selected on nutrient plates containing the antibiotic . bacteria without a plasmid will die , while bacteria carrying a plasmid can live and reproduce .
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if we place a bacteria containing rdna and another with the normal plasmid in an antibiotic medium , what will happen ?
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key points : dna cloning is a molecular biology technique that makes many identical copies of a piece of dna , such as a gene . in a typical cloning experiment , a target gene is inserted into a circular piece of dna called a plasmid . the plasmid is introduced into bacteria via process called transformation , and bacteria carrying the plasmid are selected using antibiotics . bacteria with the correct plasmid are used to make more plasmid dna or , in some cases , induced to express the gene and make protein . introduction when you hear the word “ cloning , ” you may think of the cloning of whole organisms , such as dolly the sheep . however , all it means to clone something is to make a genetically exact copy of it . in a molecular biology lab , what ’ s most often cloned is a gene or other small piece of dna . if your friend the molecular biologist say that her “ cloning ” isn ’ t working , she 's almost certainly talking about copying bits of dna , not making the next dolly ! overview of dna cloning dna cloning is the process of making multiple , identical copies of a particular piece of dna . in a typical dna cloning procedure , the gene or other dna fragment of interest ( perhaps a gene for a medically important human protein ) is first inserted into a circular piece of dna called a plasmid . the insertion is done using enzymes that “ cut and paste ” dna , and it produces a molecule of recombinant dna , or dna assembled out of fragments from multiple sources . next , the recombinant plasmid is introduced into bacteria . bacteria carrying the plasmid are selected and grown up . as they reproduce , they replicate the plasmid and pass it on to their offspring , making copies of the dna it contains . what is the point of making many copies of a dna sequence in a plasmid ? in some cases , we need lots of dna copies to conduct experiments or build new plasmids . in other cases , the piece of dna encodes a useful protein , and the bacteria are used as “ factories ” to make the protein . for instance , the human insulin gene is expressed in e. coli bacteria to make insulin used by diabetics . steps of dna cloning dna cloning is used for many purposes . as an example , let 's see how dna cloning can be used to synthesize a protein ( such as human insulin ) in bacteria . the basic steps are : cut open the plasmid and `` paste '' in the gene . this process relies on restriction enzymes ( which cut dna ) and dna ligase ( which joins dna ) . transform the plasmid into bacteria . use antibiotic selection to identify the bacteria that took up the plasmid . grow up lots of plasmid-carrying bacteria and use them as `` factories '' to make the protein . harvest the protein from the bacteria and purify it . let 's take a closer look at each step . 1 . cutting and pasting dna how can pieces of dna from different sources be joined together ? a common method uses two types of enzymes : restriction enzymes and dna ligase . a restriction enzyme is a dna-cutting enzyme that recognizes a specific target sequence and cuts dna into two pieces at or near that site . many restriction enzymes produce cut ends with short , single-stranded overhangs . if two molecules have matching overhangs , they can base-pair and stick together . however , they wo n't combine to form an unbroken dna molecule until they are joined by dna ligase , which seals gaps in the dna backbone . our goal in cloning is to insert a target gene ( e.g. , for human insulin ) into a plasmid . using a carefully chosen restriction enzyme , we digest : the plasmid , which has a single cut site the target gene fragment , which has a cut site near each end then , we combine the fragments with dna ligase , which links them to make a recombinant plasmid containing the gene . 2 . bacterial transformation and selection plasmids and other dna can be introduced into bacteria , such as the harmless e. coli used in labs , in a process called transformation . during transformation , specially prepared bacterial cells are given a shock ( such as high temperature ) that encourages them to take up foreign dna . a plasmid typically contains an antibiotic resistance gene , which allows bacteria to survive in the presence of a specific antibiotic . thus , bacteria that took up the plasmid can be selected on nutrient plates containing the antibiotic . bacteria without a plasmid will die , while bacteria carrying a plasmid can live and reproduce . each surviving bacterium will give rise to a small , dot-like group , or colony , of identical bacteria that all carry the same plasmid . not all colonies will necessarily contain the right plasmid . that ’ s because , during a ligation , dna fragments don ’ t always get “ pasted ” in exactly the way we intend . instead , we must collect dna from several colonies and see whether each one contain the right plasmid . methods like restriction enzyme digestion and pcr are commonly used to check the plasmids . 3 . protein production once we have found a bacterial colony with the right plasmid , we can grow a large culture of plasmid-bearing bacteria . then , we give the bacteria a chemical signal that instructs them to make the target protein . the bacteria serve as miniature “ factories , '' churning out large amounts of protein . for instance , if our plasmid contained the human insulin gene , the bacteria would start transcribing the gene and translating the mrna to produce many molecules of human insulin protein . once the protein has been produced , the bacterial cells can be split open to release it . there are many other proteins and macromolecules floating around in bacteria besides the target protein ( e.g. , insulin ) . because of this , the target protein must be purified , or separated from the other contents of the cells by biochemical techniques . the purified protein can be used for experiments or , in the case of insulin , administered to patients . uses of dna cloning dna molecules built through cloning techniques are used for many purposes in molecular biology . a short list of examples includes : biopharmaceuticals . dna cloning can be used to make human proteins with biomedical applications , such as the insulin mentioned above . other examples of recombinant proteins include human growth hormone , which is given to patients who are unable to synthesize the hormone , and tissue plasminogen activator ( tpa ) , which is used to treat strokes and prevent blood clots . recombinant proteins like these are often made in bacteria . gene therapy . in some genetic disorders , patients lack the functional form of a particular gene . gene therapy attempts to provide a normal copy of the gene to the cells of a patient ’ s body . for example , dna cloning was used to build plasmids containing a normal version of the gene that 's nonfunctional in cystic fibrosis . when the plasmids were delivered to the lungs of cystic fibrosis patients , lung function deteriorated less quickly $ ^2 $ . gene analysis . in basic research labs , biologists often use dna cloning to build artificial , recombinant versions of genes that help them understand how normal genes in an organism function . these are just a few examples of how dna cloning is used in biology today . dna cloning is a very common technique that is used in a huge variety of molecular biology applications .
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for instance , the human insulin gene is expressed in e. coli bacteria to make insulin used by diabetics . steps of dna cloning dna cloning is used for many purposes . as an example , let 's see how dna cloning can be used to synthesize a protein ( such as human insulin ) in bacteria .
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in `` steps of dna cloning '' step 2 , how can a plasmid be transformed into bacteria ?
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key points : dna cloning is a molecular biology technique that makes many identical copies of a piece of dna , such as a gene . in a typical cloning experiment , a target gene is inserted into a circular piece of dna called a plasmid . the plasmid is introduced into bacteria via process called transformation , and bacteria carrying the plasmid are selected using antibiotics . bacteria with the correct plasmid are used to make more plasmid dna or , in some cases , induced to express the gene and make protein . introduction when you hear the word “ cloning , ” you may think of the cloning of whole organisms , such as dolly the sheep . however , all it means to clone something is to make a genetically exact copy of it . in a molecular biology lab , what ’ s most often cloned is a gene or other small piece of dna . if your friend the molecular biologist say that her “ cloning ” isn ’ t working , she 's almost certainly talking about copying bits of dna , not making the next dolly ! overview of dna cloning dna cloning is the process of making multiple , identical copies of a particular piece of dna . in a typical dna cloning procedure , the gene or other dna fragment of interest ( perhaps a gene for a medically important human protein ) is first inserted into a circular piece of dna called a plasmid . the insertion is done using enzymes that “ cut and paste ” dna , and it produces a molecule of recombinant dna , or dna assembled out of fragments from multiple sources . next , the recombinant plasmid is introduced into bacteria . bacteria carrying the plasmid are selected and grown up . as they reproduce , they replicate the plasmid and pass it on to their offspring , making copies of the dna it contains . what is the point of making many copies of a dna sequence in a plasmid ? in some cases , we need lots of dna copies to conduct experiments or build new plasmids . in other cases , the piece of dna encodes a useful protein , and the bacteria are used as “ factories ” to make the protein . for instance , the human insulin gene is expressed in e. coli bacteria to make insulin used by diabetics . steps of dna cloning dna cloning is used for many purposes . as an example , let 's see how dna cloning can be used to synthesize a protein ( such as human insulin ) in bacteria . the basic steps are : cut open the plasmid and `` paste '' in the gene . this process relies on restriction enzymes ( which cut dna ) and dna ligase ( which joins dna ) . transform the plasmid into bacteria . use antibiotic selection to identify the bacteria that took up the plasmid . grow up lots of plasmid-carrying bacteria and use them as `` factories '' to make the protein . harvest the protein from the bacteria and purify it . let 's take a closer look at each step . 1 . cutting and pasting dna how can pieces of dna from different sources be joined together ? a common method uses two types of enzymes : restriction enzymes and dna ligase . a restriction enzyme is a dna-cutting enzyme that recognizes a specific target sequence and cuts dna into two pieces at or near that site . many restriction enzymes produce cut ends with short , single-stranded overhangs . if two molecules have matching overhangs , they can base-pair and stick together . however , they wo n't combine to form an unbroken dna molecule until they are joined by dna ligase , which seals gaps in the dna backbone . our goal in cloning is to insert a target gene ( e.g. , for human insulin ) into a plasmid . using a carefully chosen restriction enzyme , we digest : the plasmid , which has a single cut site the target gene fragment , which has a cut site near each end then , we combine the fragments with dna ligase , which links them to make a recombinant plasmid containing the gene . 2 . bacterial transformation and selection plasmids and other dna can be introduced into bacteria , such as the harmless e. coli used in labs , in a process called transformation . during transformation , specially prepared bacterial cells are given a shock ( such as high temperature ) that encourages them to take up foreign dna . a plasmid typically contains an antibiotic resistance gene , which allows bacteria to survive in the presence of a specific antibiotic . thus , bacteria that took up the plasmid can be selected on nutrient plates containing the antibiotic . bacteria without a plasmid will die , while bacteria carrying a plasmid can live and reproduce . each surviving bacterium will give rise to a small , dot-like group , or colony , of identical bacteria that all carry the same plasmid . not all colonies will necessarily contain the right plasmid . that ’ s because , during a ligation , dna fragments don ’ t always get “ pasted ” in exactly the way we intend . instead , we must collect dna from several colonies and see whether each one contain the right plasmid . methods like restriction enzyme digestion and pcr are commonly used to check the plasmids . 3 . protein production once we have found a bacterial colony with the right plasmid , we can grow a large culture of plasmid-bearing bacteria . then , we give the bacteria a chemical signal that instructs them to make the target protein . the bacteria serve as miniature “ factories , '' churning out large amounts of protein . for instance , if our plasmid contained the human insulin gene , the bacteria would start transcribing the gene and translating the mrna to produce many molecules of human insulin protein . once the protein has been produced , the bacterial cells can be split open to release it . there are many other proteins and macromolecules floating around in bacteria besides the target protein ( e.g. , insulin ) . because of this , the target protein must be purified , or separated from the other contents of the cells by biochemical techniques . the purified protein can be used for experiments or , in the case of insulin , administered to patients . uses of dna cloning dna molecules built through cloning techniques are used for many purposes in molecular biology . a short list of examples includes : biopharmaceuticals . dna cloning can be used to make human proteins with biomedical applications , such as the insulin mentioned above . other examples of recombinant proteins include human growth hormone , which is given to patients who are unable to synthesize the hormone , and tissue plasminogen activator ( tpa ) , which is used to treat strokes and prevent blood clots . recombinant proteins like these are often made in bacteria . gene therapy . in some genetic disorders , patients lack the functional form of a particular gene . gene therapy attempts to provide a normal copy of the gene to the cells of a patient ’ s body . for example , dna cloning was used to build plasmids containing a normal version of the gene that 's nonfunctional in cystic fibrosis . when the plasmids were delivered to the lungs of cystic fibrosis patients , lung function deteriorated less quickly $ ^2 $ . gene analysis . in basic research labs , biologists often use dna cloning to build artificial , recombinant versions of genes that help them understand how normal genes in an organism function . these are just a few examples of how dna cloning is used in biology today . dna cloning is a very common technique that is used in a huge variety of molecular biology applications .
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this process relies on restriction enzymes ( which cut dna ) and dna ligase ( which joins dna ) . transform the plasmid into bacteria . use antibiotic selection to identify the bacteria that took up the plasmid .
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should n't it be `` insert the plasmid into bacteria '' ?
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key points : dna cloning is a molecular biology technique that makes many identical copies of a piece of dna , such as a gene . in a typical cloning experiment , a target gene is inserted into a circular piece of dna called a plasmid . the plasmid is introduced into bacteria via process called transformation , and bacteria carrying the plasmid are selected using antibiotics . bacteria with the correct plasmid are used to make more plasmid dna or , in some cases , induced to express the gene and make protein . introduction when you hear the word “ cloning , ” you may think of the cloning of whole organisms , such as dolly the sheep . however , all it means to clone something is to make a genetically exact copy of it . in a molecular biology lab , what ’ s most often cloned is a gene or other small piece of dna . if your friend the molecular biologist say that her “ cloning ” isn ’ t working , she 's almost certainly talking about copying bits of dna , not making the next dolly ! overview of dna cloning dna cloning is the process of making multiple , identical copies of a particular piece of dna . in a typical dna cloning procedure , the gene or other dna fragment of interest ( perhaps a gene for a medically important human protein ) is first inserted into a circular piece of dna called a plasmid . the insertion is done using enzymes that “ cut and paste ” dna , and it produces a molecule of recombinant dna , or dna assembled out of fragments from multiple sources . next , the recombinant plasmid is introduced into bacteria . bacteria carrying the plasmid are selected and grown up . as they reproduce , they replicate the plasmid and pass it on to their offspring , making copies of the dna it contains . what is the point of making many copies of a dna sequence in a plasmid ? in some cases , we need lots of dna copies to conduct experiments or build new plasmids . in other cases , the piece of dna encodes a useful protein , and the bacteria are used as “ factories ” to make the protein . for instance , the human insulin gene is expressed in e. coli bacteria to make insulin used by diabetics . steps of dna cloning dna cloning is used for many purposes . as an example , let 's see how dna cloning can be used to synthesize a protein ( such as human insulin ) in bacteria . the basic steps are : cut open the plasmid and `` paste '' in the gene . this process relies on restriction enzymes ( which cut dna ) and dna ligase ( which joins dna ) . transform the plasmid into bacteria . use antibiotic selection to identify the bacteria that took up the plasmid . grow up lots of plasmid-carrying bacteria and use them as `` factories '' to make the protein . harvest the protein from the bacteria and purify it . let 's take a closer look at each step . 1 . cutting and pasting dna how can pieces of dna from different sources be joined together ? a common method uses two types of enzymes : restriction enzymes and dna ligase . a restriction enzyme is a dna-cutting enzyme that recognizes a specific target sequence and cuts dna into two pieces at or near that site . many restriction enzymes produce cut ends with short , single-stranded overhangs . if two molecules have matching overhangs , they can base-pair and stick together . however , they wo n't combine to form an unbroken dna molecule until they are joined by dna ligase , which seals gaps in the dna backbone . our goal in cloning is to insert a target gene ( e.g. , for human insulin ) into a plasmid . using a carefully chosen restriction enzyme , we digest : the plasmid , which has a single cut site the target gene fragment , which has a cut site near each end then , we combine the fragments with dna ligase , which links them to make a recombinant plasmid containing the gene . 2 . bacterial transformation and selection plasmids and other dna can be introduced into bacteria , such as the harmless e. coli used in labs , in a process called transformation . during transformation , specially prepared bacterial cells are given a shock ( such as high temperature ) that encourages them to take up foreign dna . a plasmid typically contains an antibiotic resistance gene , which allows bacteria to survive in the presence of a specific antibiotic . thus , bacteria that took up the plasmid can be selected on nutrient plates containing the antibiotic . bacteria without a plasmid will die , while bacteria carrying a plasmid can live and reproduce . each surviving bacterium will give rise to a small , dot-like group , or colony , of identical bacteria that all carry the same plasmid . not all colonies will necessarily contain the right plasmid . that ’ s because , during a ligation , dna fragments don ’ t always get “ pasted ” in exactly the way we intend . instead , we must collect dna from several colonies and see whether each one contain the right plasmid . methods like restriction enzyme digestion and pcr are commonly used to check the plasmids . 3 . protein production once we have found a bacterial colony with the right plasmid , we can grow a large culture of plasmid-bearing bacteria . then , we give the bacteria a chemical signal that instructs them to make the target protein . the bacteria serve as miniature “ factories , '' churning out large amounts of protein . for instance , if our plasmid contained the human insulin gene , the bacteria would start transcribing the gene and translating the mrna to produce many molecules of human insulin protein . once the protein has been produced , the bacterial cells can be split open to release it . there are many other proteins and macromolecules floating around in bacteria besides the target protein ( e.g. , insulin ) . because of this , the target protein must be purified , or separated from the other contents of the cells by biochemical techniques . the purified protein can be used for experiments or , in the case of insulin , administered to patients . uses of dna cloning dna molecules built through cloning techniques are used for many purposes in molecular biology . a short list of examples includes : biopharmaceuticals . dna cloning can be used to make human proteins with biomedical applications , such as the insulin mentioned above . other examples of recombinant proteins include human growth hormone , which is given to patients who are unable to synthesize the hormone , and tissue plasminogen activator ( tpa ) , which is used to treat strokes and prevent blood clots . recombinant proteins like these are often made in bacteria . gene therapy . in some genetic disorders , patients lack the functional form of a particular gene . gene therapy attempts to provide a normal copy of the gene to the cells of a patient ’ s body . for example , dna cloning was used to build plasmids containing a normal version of the gene that 's nonfunctional in cystic fibrosis . when the plasmids were delivered to the lungs of cystic fibrosis patients , lung function deteriorated less quickly $ ^2 $ . gene analysis . in basic research labs , biologists often use dna cloning to build artificial , recombinant versions of genes that help them understand how normal genes in an organism function . these are just a few examples of how dna cloning is used in biology today . dna cloning is a very common technique that is used in a huge variety of molecular biology applications .
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for instance , the human insulin gene is expressed in e. coli bacteria to make insulin used by diabetics . steps of dna cloning dna cloning is used for many purposes . as an example , let 's see how dna cloning can be used to synthesize a protein ( such as human insulin ) in bacteria .
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is there any example of how dna cloning affect the environment ?
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key points : dna cloning is a molecular biology technique that makes many identical copies of a piece of dna , such as a gene . in a typical cloning experiment , a target gene is inserted into a circular piece of dna called a plasmid . the plasmid is introduced into bacteria via process called transformation , and bacteria carrying the plasmid are selected using antibiotics . bacteria with the correct plasmid are used to make more plasmid dna or , in some cases , induced to express the gene and make protein . introduction when you hear the word “ cloning , ” you may think of the cloning of whole organisms , such as dolly the sheep . however , all it means to clone something is to make a genetically exact copy of it . in a molecular biology lab , what ’ s most often cloned is a gene or other small piece of dna . if your friend the molecular biologist say that her “ cloning ” isn ’ t working , she 's almost certainly talking about copying bits of dna , not making the next dolly ! overview of dna cloning dna cloning is the process of making multiple , identical copies of a particular piece of dna . in a typical dna cloning procedure , the gene or other dna fragment of interest ( perhaps a gene for a medically important human protein ) is first inserted into a circular piece of dna called a plasmid . the insertion is done using enzymes that “ cut and paste ” dna , and it produces a molecule of recombinant dna , or dna assembled out of fragments from multiple sources . next , the recombinant plasmid is introduced into bacteria . bacteria carrying the plasmid are selected and grown up . as they reproduce , they replicate the plasmid and pass it on to their offspring , making copies of the dna it contains . what is the point of making many copies of a dna sequence in a plasmid ? in some cases , we need lots of dna copies to conduct experiments or build new plasmids . in other cases , the piece of dna encodes a useful protein , and the bacteria are used as “ factories ” to make the protein . for instance , the human insulin gene is expressed in e. coli bacteria to make insulin used by diabetics . steps of dna cloning dna cloning is used for many purposes . as an example , let 's see how dna cloning can be used to synthesize a protein ( such as human insulin ) in bacteria . the basic steps are : cut open the plasmid and `` paste '' in the gene . this process relies on restriction enzymes ( which cut dna ) and dna ligase ( which joins dna ) . transform the plasmid into bacteria . use antibiotic selection to identify the bacteria that took up the plasmid . grow up lots of plasmid-carrying bacteria and use them as `` factories '' to make the protein . harvest the protein from the bacteria and purify it . let 's take a closer look at each step . 1 . cutting and pasting dna how can pieces of dna from different sources be joined together ? a common method uses two types of enzymes : restriction enzymes and dna ligase . a restriction enzyme is a dna-cutting enzyme that recognizes a specific target sequence and cuts dna into two pieces at or near that site . many restriction enzymes produce cut ends with short , single-stranded overhangs . if two molecules have matching overhangs , they can base-pair and stick together . however , they wo n't combine to form an unbroken dna molecule until they are joined by dna ligase , which seals gaps in the dna backbone . our goal in cloning is to insert a target gene ( e.g. , for human insulin ) into a plasmid . using a carefully chosen restriction enzyme , we digest : the plasmid , which has a single cut site the target gene fragment , which has a cut site near each end then , we combine the fragments with dna ligase , which links them to make a recombinant plasmid containing the gene . 2 . bacterial transformation and selection plasmids and other dna can be introduced into bacteria , such as the harmless e. coli used in labs , in a process called transformation . during transformation , specially prepared bacterial cells are given a shock ( such as high temperature ) that encourages them to take up foreign dna . a plasmid typically contains an antibiotic resistance gene , which allows bacteria to survive in the presence of a specific antibiotic . thus , bacteria that took up the plasmid can be selected on nutrient plates containing the antibiotic . bacteria without a plasmid will die , while bacteria carrying a plasmid can live and reproduce . each surviving bacterium will give rise to a small , dot-like group , or colony , of identical bacteria that all carry the same plasmid . not all colonies will necessarily contain the right plasmid . that ’ s because , during a ligation , dna fragments don ’ t always get “ pasted ” in exactly the way we intend . instead , we must collect dna from several colonies and see whether each one contain the right plasmid . methods like restriction enzyme digestion and pcr are commonly used to check the plasmids . 3 . protein production once we have found a bacterial colony with the right plasmid , we can grow a large culture of plasmid-bearing bacteria . then , we give the bacteria a chemical signal that instructs them to make the target protein . the bacteria serve as miniature “ factories , '' churning out large amounts of protein . for instance , if our plasmid contained the human insulin gene , the bacteria would start transcribing the gene and translating the mrna to produce many molecules of human insulin protein . once the protein has been produced , the bacterial cells can be split open to release it . there are many other proteins and macromolecules floating around in bacteria besides the target protein ( e.g. , insulin ) . because of this , the target protein must be purified , or separated from the other contents of the cells by biochemical techniques . the purified protein can be used for experiments or , in the case of insulin , administered to patients . uses of dna cloning dna molecules built through cloning techniques are used for many purposes in molecular biology . a short list of examples includes : biopharmaceuticals . dna cloning can be used to make human proteins with biomedical applications , such as the insulin mentioned above . other examples of recombinant proteins include human growth hormone , which is given to patients who are unable to synthesize the hormone , and tissue plasminogen activator ( tpa ) , which is used to treat strokes and prevent blood clots . recombinant proteins like these are often made in bacteria . gene therapy . in some genetic disorders , patients lack the functional form of a particular gene . gene therapy attempts to provide a normal copy of the gene to the cells of a patient ’ s body . for example , dna cloning was used to build plasmids containing a normal version of the gene that 's nonfunctional in cystic fibrosis . when the plasmids were delivered to the lungs of cystic fibrosis patients , lung function deteriorated less quickly $ ^2 $ . gene analysis . in basic research labs , biologists often use dna cloning to build artificial , recombinant versions of genes that help them understand how normal genes in an organism function . these are just a few examples of how dna cloning is used in biology today . dna cloning is a very common technique that is used in a huge variety of molecular biology applications .
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this process relies on restriction enzymes ( which cut dna ) and dna ligase ( which joins dna ) . transform the plasmid into bacteria . use antibiotic selection to identify the bacteria that took up the plasmid .
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hey , is it possible to cut something out of the bacteria before you add ?
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key points : dna cloning is a molecular biology technique that makes many identical copies of a piece of dna , such as a gene . in a typical cloning experiment , a target gene is inserted into a circular piece of dna called a plasmid . the plasmid is introduced into bacteria via process called transformation , and bacteria carrying the plasmid are selected using antibiotics . bacteria with the correct plasmid are used to make more plasmid dna or , in some cases , induced to express the gene and make protein . introduction when you hear the word “ cloning , ” you may think of the cloning of whole organisms , such as dolly the sheep . however , all it means to clone something is to make a genetically exact copy of it . in a molecular biology lab , what ’ s most often cloned is a gene or other small piece of dna . if your friend the molecular biologist say that her “ cloning ” isn ’ t working , she 's almost certainly talking about copying bits of dna , not making the next dolly ! overview of dna cloning dna cloning is the process of making multiple , identical copies of a particular piece of dna . in a typical dna cloning procedure , the gene or other dna fragment of interest ( perhaps a gene for a medically important human protein ) is first inserted into a circular piece of dna called a plasmid . the insertion is done using enzymes that “ cut and paste ” dna , and it produces a molecule of recombinant dna , or dna assembled out of fragments from multiple sources . next , the recombinant plasmid is introduced into bacteria . bacteria carrying the plasmid are selected and grown up . as they reproduce , they replicate the plasmid and pass it on to their offspring , making copies of the dna it contains . what is the point of making many copies of a dna sequence in a plasmid ? in some cases , we need lots of dna copies to conduct experiments or build new plasmids . in other cases , the piece of dna encodes a useful protein , and the bacteria are used as “ factories ” to make the protein . for instance , the human insulin gene is expressed in e. coli bacteria to make insulin used by diabetics . steps of dna cloning dna cloning is used for many purposes . as an example , let 's see how dna cloning can be used to synthesize a protein ( such as human insulin ) in bacteria . the basic steps are : cut open the plasmid and `` paste '' in the gene . this process relies on restriction enzymes ( which cut dna ) and dna ligase ( which joins dna ) . transform the plasmid into bacteria . use antibiotic selection to identify the bacteria that took up the plasmid . grow up lots of plasmid-carrying bacteria and use them as `` factories '' to make the protein . harvest the protein from the bacteria and purify it . let 's take a closer look at each step . 1 . cutting and pasting dna how can pieces of dna from different sources be joined together ? a common method uses two types of enzymes : restriction enzymes and dna ligase . a restriction enzyme is a dna-cutting enzyme that recognizes a specific target sequence and cuts dna into two pieces at or near that site . many restriction enzymes produce cut ends with short , single-stranded overhangs . if two molecules have matching overhangs , they can base-pair and stick together . however , they wo n't combine to form an unbroken dna molecule until they are joined by dna ligase , which seals gaps in the dna backbone . our goal in cloning is to insert a target gene ( e.g. , for human insulin ) into a plasmid . using a carefully chosen restriction enzyme , we digest : the plasmid , which has a single cut site the target gene fragment , which has a cut site near each end then , we combine the fragments with dna ligase , which links them to make a recombinant plasmid containing the gene . 2 . bacterial transformation and selection plasmids and other dna can be introduced into bacteria , such as the harmless e. coli used in labs , in a process called transformation . during transformation , specially prepared bacterial cells are given a shock ( such as high temperature ) that encourages them to take up foreign dna . a plasmid typically contains an antibiotic resistance gene , which allows bacteria to survive in the presence of a specific antibiotic . thus , bacteria that took up the plasmid can be selected on nutrient plates containing the antibiotic . bacteria without a plasmid will die , while bacteria carrying a plasmid can live and reproduce . each surviving bacterium will give rise to a small , dot-like group , or colony , of identical bacteria that all carry the same plasmid . not all colonies will necessarily contain the right plasmid . that ’ s because , during a ligation , dna fragments don ’ t always get “ pasted ” in exactly the way we intend . instead , we must collect dna from several colonies and see whether each one contain the right plasmid . methods like restriction enzyme digestion and pcr are commonly used to check the plasmids . 3 . protein production once we have found a bacterial colony with the right plasmid , we can grow a large culture of plasmid-bearing bacteria . then , we give the bacteria a chemical signal that instructs them to make the target protein . the bacteria serve as miniature “ factories , '' churning out large amounts of protein . for instance , if our plasmid contained the human insulin gene , the bacteria would start transcribing the gene and translating the mrna to produce many molecules of human insulin protein . once the protein has been produced , the bacterial cells can be split open to release it . there are many other proteins and macromolecules floating around in bacteria besides the target protein ( e.g. , insulin ) . because of this , the target protein must be purified , or separated from the other contents of the cells by biochemical techniques . the purified protein can be used for experiments or , in the case of insulin , administered to patients . uses of dna cloning dna molecules built through cloning techniques are used for many purposes in molecular biology . a short list of examples includes : biopharmaceuticals . dna cloning can be used to make human proteins with biomedical applications , such as the insulin mentioned above . other examples of recombinant proteins include human growth hormone , which is given to patients who are unable to synthesize the hormone , and tissue plasminogen activator ( tpa ) , which is used to treat strokes and prevent blood clots . recombinant proteins like these are often made in bacteria . gene therapy . in some genetic disorders , patients lack the functional form of a particular gene . gene therapy attempts to provide a normal copy of the gene to the cells of a patient ’ s body . for example , dna cloning was used to build plasmids containing a normal version of the gene that 's nonfunctional in cystic fibrosis . when the plasmids were delivered to the lungs of cystic fibrosis patients , lung function deteriorated less quickly $ ^2 $ . gene analysis . in basic research labs , biologists often use dna cloning to build artificial , recombinant versions of genes that help them understand how normal genes in an organism function . these are just a few examples of how dna cloning is used in biology today . dna cloning is a very common technique that is used in a huge variety of molecular biology applications .
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the basic steps are : cut open the plasmid and `` paste '' in the gene . this process relies on restriction enzymes ( which cut dna ) and dna ligase ( which joins dna ) . transform the plasmid into bacteria . use antibiotic selection to identify the bacteria that took up the plasmid .
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maybe change the bacteria 's color by cutting out the existing color dna and putting a new color strand in the plasmid ?
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key points : dna cloning is a molecular biology technique that makes many identical copies of a piece of dna , such as a gene . in a typical cloning experiment , a target gene is inserted into a circular piece of dna called a plasmid . the plasmid is introduced into bacteria via process called transformation , and bacteria carrying the plasmid are selected using antibiotics . bacteria with the correct plasmid are used to make more plasmid dna or , in some cases , induced to express the gene and make protein . introduction when you hear the word “ cloning , ” you may think of the cloning of whole organisms , such as dolly the sheep . however , all it means to clone something is to make a genetically exact copy of it . in a molecular biology lab , what ’ s most often cloned is a gene or other small piece of dna . if your friend the molecular biologist say that her “ cloning ” isn ’ t working , she 's almost certainly talking about copying bits of dna , not making the next dolly ! overview of dna cloning dna cloning is the process of making multiple , identical copies of a particular piece of dna . in a typical dna cloning procedure , the gene or other dna fragment of interest ( perhaps a gene for a medically important human protein ) is first inserted into a circular piece of dna called a plasmid . the insertion is done using enzymes that “ cut and paste ” dna , and it produces a molecule of recombinant dna , or dna assembled out of fragments from multiple sources . next , the recombinant plasmid is introduced into bacteria . bacteria carrying the plasmid are selected and grown up . as they reproduce , they replicate the plasmid and pass it on to their offspring , making copies of the dna it contains . what is the point of making many copies of a dna sequence in a plasmid ? in some cases , we need lots of dna copies to conduct experiments or build new plasmids . in other cases , the piece of dna encodes a useful protein , and the bacteria are used as “ factories ” to make the protein . for instance , the human insulin gene is expressed in e. coli bacteria to make insulin used by diabetics . steps of dna cloning dna cloning is used for many purposes . as an example , let 's see how dna cloning can be used to synthesize a protein ( such as human insulin ) in bacteria . the basic steps are : cut open the plasmid and `` paste '' in the gene . this process relies on restriction enzymes ( which cut dna ) and dna ligase ( which joins dna ) . transform the plasmid into bacteria . use antibiotic selection to identify the bacteria that took up the plasmid . grow up lots of plasmid-carrying bacteria and use them as `` factories '' to make the protein . harvest the protein from the bacteria and purify it . let 's take a closer look at each step . 1 . cutting and pasting dna how can pieces of dna from different sources be joined together ? a common method uses two types of enzymes : restriction enzymes and dna ligase . a restriction enzyme is a dna-cutting enzyme that recognizes a specific target sequence and cuts dna into two pieces at or near that site . many restriction enzymes produce cut ends with short , single-stranded overhangs . if two molecules have matching overhangs , they can base-pair and stick together . however , they wo n't combine to form an unbroken dna molecule until they are joined by dna ligase , which seals gaps in the dna backbone . our goal in cloning is to insert a target gene ( e.g. , for human insulin ) into a plasmid . using a carefully chosen restriction enzyme , we digest : the plasmid , which has a single cut site the target gene fragment , which has a cut site near each end then , we combine the fragments with dna ligase , which links them to make a recombinant plasmid containing the gene . 2 . bacterial transformation and selection plasmids and other dna can be introduced into bacteria , such as the harmless e. coli used in labs , in a process called transformation . during transformation , specially prepared bacterial cells are given a shock ( such as high temperature ) that encourages them to take up foreign dna . a plasmid typically contains an antibiotic resistance gene , which allows bacteria to survive in the presence of a specific antibiotic . thus , bacteria that took up the plasmid can be selected on nutrient plates containing the antibiotic . bacteria without a plasmid will die , while bacteria carrying a plasmid can live and reproduce . each surviving bacterium will give rise to a small , dot-like group , or colony , of identical bacteria that all carry the same plasmid . not all colonies will necessarily contain the right plasmid . that ’ s because , during a ligation , dna fragments don ’ t always get “ pasted ” in exactly the way we intend . instead , we must collect dna from several colonies and see whether each one contain the right plasmid . methods like restriction enzyme digestion and pcr are commonly used to check the plasmids . 3 . protein production once we have found a bacterial colony with the right plasmid , we can grow a large culture of plasmid-bearing bacteria . then , we give the bacteria a chemical signal that instructs them to make the target protein . the bacteria serve as miniature “ factories , '' churning out large amounts of protein . for instance , if our plasmid contained the human insulin gene , the bacteria would start transcribing the gene and translating the mrna to produce many molecules of human insulin protein . once the protein has been produced , the bacterial cells can be split open to release it . there are many other proteins and macromolecules floating around in bacteria besides the target protein ( e.g. , insulin ) . because of this , the target protein must be purified , or separated from the other contents of the cells by biochemical techniques . the purified protein can be used for experiments or , in the case of insulin , administered to patients . uses of dna cloning dna molecules built through cloning techniques are used for many purposes in molecular biology . a short list of examples includes : biopharmaceuticals . dna cloning can be used to make human proteins with biomedical applications , such as the insulin mentioned above . other examples of recombinant proteins include human growth hormone , which is given to patients who are unable to synthesize the hormone , and tissue plasminogen activator ( tpa ) , which is used to treat strokes and prevent blood clots . recombinant proteins like these are often made in bacteria . gene therapy . in some genetic disorders , patients lack the functional form of a particular gene . gene therapy attempts to provide a normal copy of the gene to the cells of a patient ’ s body . for example , dna cloning was used to build plasmids containing a normal version of the gene that 's nonfunctional in cystic fibrosis . when the plasmids were delivered to the lungs of cystic fibrosis patients , lung function deteriorated less quickly $ ^2 $ . gene analysis . in basic research labs , biologists often use dna cloning to build artificial , recombinant versions of genes that help them understand how normal genes in an organism function . these are just a few examples of how dna cloning is used in biology today . dna cloning is a very common technique that is used in a huge variety of molecular biology applications .
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for instance , the human insulin gene is expressed in e. coli bacteria to make insulin used by diabetics . steps of dna cloning dna cloning is used for many purposes . as an example , let 's see how dna cloning can be used to synthesize a protein ( such as human insulin ) in bacteria .
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what are some of the biochemical techniques that can be used to purify a target protein after dna cloning and transformation ?
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key points : dna cloning is a molecular biology technique that makes many identical copies of a piece of dna , such as a gene . in a typical cloning experiment , a target gene is inserted into a circular piece of dna called a plasmid . the plasmid is introduced into bacteria via process called transformation , and bacteria carrying the plasmid are selected using antibiotics . bacteria with the correct plasmid are used to make more plasmid dna or , in some cases , induced to express the gene and make protein . introduction when you hear the word “ cloning , ” you may think of the cloning of whole organisms , such as dolly the sheep . however , all it means to clone something is to make a genetically exact copy of it . in a molecular biology lab , what ’ s most often cloned is a gene or other small piece of dna . if your friend the molecular biologist say that her “ cloning ” isn ’ t working , she 's almost certainly talking about copying bits of dna , not making the next dolly ! overview of dna cloning dna cloning is the process of making multiple , identical copies of a particular piece of dna . in a typical dna cloning procedure , the gene or other dna fragment of interest ( perhaps a gene for a medically important human protein ) is first inserted into a circular piece of dna called a plasmid . the insertion is done using enzymes that “ cut and paste ” dna , and it produces a molecule of recombinant dna , or dna assembled out of fragments from multiple sources . next , the recombinant plasmid is introduced into bacteria . bacteria carrying the plasmid are selected and grown up . as they reproduce , they replicate the plasmid and pass it on to their offspring , making copies of the dna it contains . what is the point of making many copies of a dna sequence in a plasmid ? in some cases , we need lots of dna copies to conduct experiments or build new plasmids . in other cases , the piece of dna encodes a useful protein , and the bacteria are used as “ factories ” to make the protein . for instance , the human insulin gene is expressed in e. coli bacteria to make insulin used by diabetics . steps of dna cloning dna cloning is used for many purposes . as an example , let 's see how dna cloning can be used to synthesize a protein ( such as human insulin ) in bacteria . the basic steps are : cut open the plasmid and `` paste '' in the gene . this process relies on restriction enzymes ( which cut dna ) and dna ligase ( which joins dna ) . transform the plasmid into bacteria . use antibiotic selection to identify the bacteria that took up the plasmid . grow up lots of plasmid-carrying bacteria and use them as `` factories '' to make the protein . harvest the protein from the bacteria and purify it . let 's take a closer look at each step . 1 . cutting and pasting dna how can pieces of dna from different sources be joined together ? a common method uses two types of enzymes : restriction enzymes and dna ligase . a restriction enzyme is a dna-cutting enzyme that recognizes a specific target sequence and cuts dna into two pieces at or near that site . many restriction enzymes produce cut ends with short , single-stranded overhangs . if two molecules have matching overhangs , they can base-pair and stick together . however , they wo n't combine to form an unbroken dna molecule until they are joined by dna ligase , which seals gaps in the dna backbone . our goal in cloning is to insert a target gene ( e.g. , for human insulin ) into a plasmid . using a carefully chosen restriction enzyme , we digest : the plasmid , which has a single cut site the target gene fragment , which has a cut site near each end then , we combine the fragments with dna ligase , which links them to make a recombinant plasmid containing the gene . 2 . bacterial transformation and selection plasmids and other dna can be introduced into bacteria , such as the harmless e. coli used in labs , in a process called transformation . during transformation , specially prepared bacterial cells are given a shock ( such as high temperature ) that encourages them to take up foreign dna . a plasmid typically contains an antibiotic resistance gene , which allows bacteria to survive in the presence of a specific antibiotic . thus , bacteria that took up the plasmid can be selected on nutrient plates containing the antibiotic . bacteria without a plasmid will die , while bacteria carrying a plasmid can live and reproduce . each surviving bacterium will give rise to a small , dot-like group , or colony , of identical bacteria that all carry the same plasmid . not all colonies will necessarily contain the right plasmid . that ’ s because , during a ligation , dna fragments don ’ t always get “ pasted ” in exactly the way we intend . instead , we must collect dna from several colonies and see whether each one contain the right plasmid . methods like restriction enzyme digestion and pcr are commonly used to check the plasmids . 3 . protein production once we have found a bacterial colony with the right plasmid , we can grow a large culture of plasmid-bearing bacteria . then , we give the bacteria a chemical signal that instructs them to make the target protein . the bacteria serve as miniature “ factories , '' churning out large amounts of protein . for instance , if our plasmid contained the human insulin gene , the bacteria would start transcribing the gene and translating the mrna to produce many molecules of human insulin protein . once the protein has been produced , the bacterial cells can be split open to release it . there are many other proteins and macromolecules floating around in bacteria besides the target protein ( e.g. , insulin ) . because of this , the target protein must be purified , or separated from the other contents of the cells by biochemical techniques . the purified protein can be used for experiments or , in the case of insulin , administered to patients . uses of dna cloning dna molecules built through cloning techniques are used for many purposes in molecular biology . a short list of examples includes : biopharmaceuticals . dna cloning can be used to make human proteins with biomedical applications , such as the insulin mentioned above . other examples of recombinant proteins include human growth hormone , which is given to patients who are unable to synthesize the hormone , and tissue plasminogen activator ( tpa ) , which is used to treat strokes and prevent blood clots . recombinant proteins like these are often made in bacteria . gene therapy . in some genetic disorders , patients lack the functional form of a particular gene . gene therapy attempts to provide a normal copy of the gene to the cells of a patient ’ s body . for example , dna cloning was used to build plasmids containing a normal version of the gene that 's nonfunctional in cystic fibrosis . when the plasmids were delivered to the lungs of cystic fibrosis patients , lung function deteriorated less quickly $ ^2 $ . gene analysis . in basic research labs , biologists often use dna cloning to build artificial , recombinant versions of genes that help them understand how normal genes in an organism function . these are just a few examples of how dna cloning is used in biology today . dna cloning is a very common technique that is used in a huge variety of molecular biology applications .
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bacterial transformation and selection plasmids and other dna can be introduced into bacteria , such as the harmless e. coli used in labs , in a process called transformation . during transformation , specially prepared bacterial cells are given a shock ( such as high temperature ) that encourages them to take up foreign dna . a plasmid typically contains an antibiotic resistance gene , which allows bacteria to survive in the presence of a specific antibiotic .
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if prepared bacterial cells were given a cold shock instead of a heat shock , would transformation occur ?
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key points : dna cloning is a molecular biology technique that makes many identical copies of a piece of dna , such as a gene . in a typical cloning experiment , a target gene is inserted into a circular piece of dna called a plasmid . the plasmid is introduced into bacteria via process called transformation , and bacteria carrying the plasmid are selected using antibiotics . bacteria with the correct plasmid are used to make more plasmid dna or , in some cases , induced to express the gene and make protein . introduction when you hear the word “ cloning , ” you may think of the cloning of whole organisms , such as dolly the sheep . however , all it means to clone something is to make a genetically exact copy of it . in a molecular biology lab , what ’ s most often cloned is a gene or other small piece of dna . if your friend the molecular biologist say that her “ cloning ” isn ’ t working , she 's almost certainly talking about copying bits of dna , not making the next dolly ! overview of dna cloning dna cloning is the process of making multiple , identical copies of a particular piece of dna . in a typical dna cloning procedure , the gene or other dna fragment of interest ( perhaps a gene for a medically important human protein ) is first inserted into a circular piece of dna called a plasmid . the insertion is done using enzymes that “ cut and paste ” dna , and it produces a molecule of recombinant dna , or dna assembled out of fragments from multiple sources . next , the recombinant plasmid is introduced into bacteria . bacteria carrying the plasmid are selected and grown up . as they reproduce , they replicate the plasmid and pass it on to their offspring , making copies of the dna it contains . what is the point of making many copies of a dna sequence in a plasmid ? in some cases , we need lots of dna copies to conduct experiments or build new plasmids . in other cases , the piece of dna encodes a useful protein , and the bacteria are used as “ factories ” to make the protein . for instance , the human insulin gene is expressed in e. coli bacteria to make insulin used by diabetics . steps of dna cloning dna cloning is used for many purposes . as an example , let 's see how dna cloning can be used to synthesize a protein ( such as human insulin ) in bacteria . the basic steps are : cut open the plasmid and `` paste '' in the gene . this process relies on restriction enzymes ( which cut dna ) and dna ligase ( which joins dna ) . transform the plasmid into bacteria . use antibiotic selection to identify the bacteria that took up the plasmid . grow up lots of plasmid-carrying bacteria and use them as `` factories '' to make the protein . harvest the protein from the bacteria and purify it . let 's take a closer look at each step . 1 . cutting and pasting dna how can pieces of dna from different sources be joined together ? a common method uses two types of enzymes : restriction enzymes and dna ligase . a restriction enzyme is a dna-cutting enzyme that recognizes a specific target sequence and cuts dna into two pieces at or near that site . many restriction enzymes produce cut ends with short , single-stranded overhangs . if two molecules have matching overhangs , they can base-pair and stick together . however , they wo n't combine to form an unbroken dna molecule until they are joined by dna ligase , which seals gaps in the dna backbone . our goal in cloning is to insert a target gene ( e.g. , for human insulin ) into a plasmid . using a carefully chosen restriction enzyme , we digest : the plasmid , which has a single cut site the target gene fragment , which has a cut site near each end then , we combine the fragments with dna ligase , which links them to make a recombinant plasmid containing the gene . 2 . bacterial transformation and selection plasmids and other dna can be introduced into bacteria , such as the harmless e. coli used in labs , in a process called transformation . during transformation , specially prepared bacterial cells are given a shock ( such as high temperature ) that encourages them to take up foreign dna . a plasmid typically contains an antibiotic resistance gene , which allows bacteria to survive in the presence of a specific antibiotic . thus , bacteria that took up the plasmid can be selected on nutrient plates containing the antibiotic . bacteria without a plasmid will die , while bacteria carrying a plasmid can live and reproduce . each surviving bacterium will give rise to a small , dot-like group , or colony , of identical bacteria that all carry the same plasmid . not all colonies will necessarily contain the right plasmid . that ’ s because , during a ligation , dna fragments don ’ t always get “ pasted ” in exactly the way we intend . instead , we must collect dna from several colonies and see whether each one contain the right plasmid . methods like restriction enzyme digestion and pcr are commonly used to check the plasmids . 3 . protein production once we have found a bacterial colony with the right plasmid , we can grow a large culture of plasmid-bearing bacteria . then , we give the bacteria a chemical signal that instructs them to make the target protein . the bacteria serve as miniature “ factories , '' churning out large amounts of protein . for instance , if our plasmid contained the human insulin gene , the bacteria would start transcribing the gene and translating the mrna to produce many molecules of human insulin protein . once the protein has been produced , the bacterial cells can be split open to release it . there are many other proteins and macromolecules floating around in bacteria besides the target protein ( e.g. , insulin ) . because of this , the target protein must be purified , or separated from the other contents of the cells by biochemical techniques . the purified protein can be used for experiments or , in the case of insulin , administered to patients . uses of dna cloning dna molecules built through cloning techniques are used for many purposes in molecular biology . a short list of examples includes : biopharmaceuticals . dna cloning can be used to make human proteins with biomedical applications , such as the insulin mentioned above . other examples of recombinant proteins include human growth hormone , which is given to patients who are unable to synthesize the hormone , and tissue plasminogen activator ( tpa ) , which is used to treat strokes and prevent blood clots . recombinant proteins like these are often made in bacteria . gene therapy . in some genetic disorders , patients lack the functional form of a particular gene . gene therapy attempts to provide a normal copy of the gene to the cells of a patient ’ s body . for example , dna cloning was used to build plasmids containing a normal version of the gene that 's nonfunctional in cystic fibrosis . when the plasmids were delivered to the lungs of cystic fibrosis patients , lung function deteriorated less quickly $ ^2 $ . gene analysis . in basic research labs , biologists often use dna cloning to build artificial , recombinant versions of genes that help them understand how normal genes in an organism function . these are just a few examples of how dna cloning is used in biology today . dna cloning is a very common technique that is used in a huge variety of molecular biology applications .
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bacterial transformation and selection plasmids and other dna can be introduced into bacteria , such as the harmless e. coli used in labs , in a process called transformation . during transformation , specially prepared bacterial cells are given a shock ( such as high temperature ) that encourages them to take up foreign dna . a plasmid typically contains an antibiotic resistance gene , which allows bacteria to survive in the presence of a specific antibiotic .
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the reason why only some cells take the plasmids is because they have different permeability or is it something else ?
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key points : dna cloning is a molecular biology technique that makes many identical copies of a piece of dna , such as a gene . in a typical cloning experiment , a target gene is inserted into a circular piece of dna called a plasmid . the plasmid is introduced into bacteria via process called transformation , and bacteria carrying the plasmid are selected using antibiotics . bacteria with the correct plasmid are used to make more plasmid dna or , in some cases , induced to express the gene and make protein . introduction when you hear the word “ cloning , ” you may think of the cloning of whole organisms , such as dolly the sheep . however , all it means to clone something is to make a genetically exact copy of it . in a molecular biology lab , what ’ s most often cloned is a gene or other small piece of dna . if your friend the molecular biologist say that her “ cloning ” isn ’ t working , she 's almost certainly talking about copying bits of dna , not making the next dolly ! overview of dna cloning dna cloning is the process of making multiple , identical copies of a particular piece of dna . in a typical dna cloning procedure , the gene or other dna fragment of interest ( perhaps a gene for a medically important human protein ) is first inserted into a circular piece of dna called a plasmid . the insertion is done using enzymes that “ cut and paste ” dna , and it produces a molecule of recombinant dna , or dna assembled out of fragments from multiple sources . next , the recombinant plasmid is introduced into bacteria . bacteria carrying the plasmid are selected and grown up . as they reproduce , they replicate the plasmid and pass it on to their offspring , making copies of the dna it contains . what is the point of making many copies of a dna sequence in a plasmid ? in some cases , we need lots of dna copies to conduct experiments or build new plasmids . in other cases , the piece of dna encodes a useful protein , and the bacteria are used as “ factories ” to make the protein . for instance , the human insulin gene is expressed in e. coli bacteria to make insulin used by diabetics . steps of dna cloning dna cloning is used for many purposes . as an example , let 's see how dna cloning can be used to synthesize a protein ( such as human insulin ) in bacteria . the basic steps are : cut open the plasmid and `` paste '' in the gene . this process relies on restriction enzymes ( which cut dna ) and dna ligase ( which joins dna ) . transform the plasmid into bacteria . use antibiotic selection to identify the bacteria that took up the plasmid . grow up lots of plasmid-carrying bacteria and use them as `` factories '' to make the protein . harvest the protein from the bacteria and purify it . let 's take a closer look at each step . 1 . cutting and pasting dna how can pieces of dna from different sources be joined together ? a common method uses two types of enzymes : restriction enzymes and dna ligase . a restriction enzyme is a dna-cutting enzyme that recognizes a specific target sequence and cuts dna into two pieces at or near that site . many restriction enzymes produce cut ends with short , single-stranded overhangs . if two molecules have matching overhangs , they can base-pair and stick together . however , they wo n't combine to form an unbroken dna molecule until they are joined by dna ligase , which seals gaps in the dna backbone . our goal in cloning is to insert a target gene ( e.g. , for human insulin ) into a plasmid . using a carefully chosen restriction enzyme , we digest : the plasmid , which has a single cut site the target gene fragment , which has a cut site near each end then , we combine the fragments with dna ligase , which links them to make a recombinant plasmid containing the gene . 2 . bacterial transformation and selection plasmids and other dna can be introduced into bacteria , such as the harmless e. coli used in labs , in a process called transformation . during transformation , specially prepared bacterial cells are given a shock ( such as high temperature ) that encourages them to take up foreign dna . a plasmid typically contains an antibiotic resistance gene , which allows bacteria to survive in the presence of a specific antibiotic . thus , bacteria that took up the plasmid can be selected on nutrient plates containing the antibiotic . bacteria without a plasmid will die , while bacteria carrying a plasmid can live and reproduce . each surviving bacterium will give rise to a small , dot-like group , or colony , of identical bacteria that all carry the same plasmid . not all colonies will necessarily contain the right plasmid . that ’ s because , during a ligation , dna fragments don ’ t always get “ pasted ” in exactly the way we intend . instead , we must collect dna from several colonies and see whether each one contain the right plasmid . methods like restriction enzyme digestion and pcr are commonly used to check the plasmids . 3 . protein production once we have found a bacterial colony with the right plasmid , we can grow a large culture of plasmid-bearing bacteria . then , we give the bacteria a chemical signal that instructs them to make the target protein . the bacteria serve as miniature “ factories , '' churning out large amounts of protein . for instance , if our plasmid contained the human insulin gene , the bacteria would start transcribing the gene and translating the mrna to produce many molecules of human insulin protein . once the protein has been produced , the bacterial cells can be split open to release it . there are many other proteins and macromolecules floating around in bacteria besides the target protein ( e.g. , insulin ) . because of this , the target protein must be purified , or separated from the other contents of the cells by biochemical techniques . the purified protein can be used for experiments or , in the case of insulin , administered to patients . uses of dna cloning dna molecules built through cloning techniques are used for many purposes in molecular biology . a short list of examples includes : biopharmaceuticals . dna cloning can be used to make human proteins with biomedical applications , such as the insulin mentioned above . other examples of recombinant proteins include human growth hormone , which is given to patients who are unable to synthesize the hormone , and tissue plasminogen activator ( tpa ) , which is used to treat strokes and prevent blood clots . recombinant proteins like these are often made in bacteria . gene therapy . in some genetic disorders , patients lack the functional form of a particular gene . gene therapy attempts to provide a normal copy of the gene to the cells of a patient ’ s body . for example , dna cloning was used to build plasmids containing a normal version of the gene that 's nonfunctional in cystic fibrosis . when the plasmids were delivered to the lungs of cystic fibrosis patients , lung function deteriorated less quickly $ ^2 $ . gene analysis . in basic research labs , biologists often use dna cloning to build artificial , recombinant versions of genes that help them understand how normal genes in an organism function . these are just a few examples of how dna cloning is used in biology today . dna cloning is a very common technique that is used in a huge variety of molecular biology applications .
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the basic steps are : cut open the plasmid and `` paste '' in the gene . this process relies on restriction enzymes ( which cut dna ) and dna ligase ( which joins dna ) . transform the plasmid into bacteria . use antibiotic selection to identify the bacteria that took up the plasmid .
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do the plasmid used to carry the dna fragment to the bacteria come from human cells ?
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key points : dna cloning is a molecular biology technique that makes many identical copies of a piece of dna , such as a gene . in a typical cloning experiment , a target gene is inserted into a circular piece of dna called a plasmid . the plasmid is introduced into bacteria via process called transformation , and bacteria carrying the plasmid are selected using antibiotics . bacteria with the correct plasmid are used to make more plasmid dna or , in some cases , induced to express the gene and make protein . introduction when you hear the word “ cloning , ” you may think of the cloning of whole organisms , such as dolly the sheep . however , all it means to clone something is to make a genetically exact copy of it . in a molecular biology lab , what ’ s most often cloned is a gene or other small piece of dna . if your friend the molecular biologist say that her “ cloning ” isn ’ t working , she 's almost certainly talking about copying bits of dna , not making the next dolly ! overview of dna cloning dna cloning is the process of making multiple , identical copies of a particular piece of dna . in a typical dna cloning procedure , the gene or other dna fragment of interest ( perhaps a gene for a medically important human protein ) is first inserted into a circular piece of dna called a plasmid . the insertion is done using enzymes that “ cut and paste ” dna , and it produces a molecule of recombinant dna , or dna assembled out of fragments from multiple sources . next , the recombinant plasmid is introduced into bacteria . bacteria carrying the plasmid are selected and grown up . as they reproduce , they replicate the plasmid and pass it on to their offspring , making copies of the dna it contains . what is the point of making many copies of a dna sequence in a plasmid ? in some cases , we need lots of dna copies to conduct experiments or build new plasmids . in other cases , the piece of dna encodes a useful protein , and the bacteria are used as “ factories ” to make the protein . for instance , the human insulin gene is expressed in e. coli bacteria to make insulin used by diabetics . steps of dna cloning dna cloning is used for many purposes . as an example , let 's see how dna cloning can be used to synthesize a protein ( such as human insulin ) in bacteria . the basic steps are : cut open the plasmid and `` paste '' in the gene . this process relies on restriction enzymes ( which cut dna ) and dna ligase ( which joins dna ) . transform the plasmid into bacteria . use antibiotic selection to identify the bacteria that took up the plasmid . grow up lots of plasmid-carrying bacteria and use them as `` factories '' to make the protein . harvest the protein from the bacteria and purify it . let 's take a closer look at each step . 1 . cutting and pasting dna how can pieces of dna from different sources be joined together ? a common method uses two types of enzymes : restriction enzymes and dna ligase . a restriction enzyme is a dna-cutting enzyme that recognizes a specific target sequence and cuts dna into two pieces at or near that site . many restriction enzymes produce cut ends with short , single-stranded overhangs . if two molecules have matching overhangs , they can base-pair and stick together . however , they wo n't combine to form an unbroken dna molecule until they are joined by dna ligase , which seals gaps in the dna backbone . our goal in cloning is to insert a target gene ( e.g. , for human insulin ) into a plasmid . using a carefully chosen restriction enzyme , we digest : the plasmid , which has a single cut site the target gene fragment , which has a cut site near each end then , we combine the fragments with dna ligase , which links them to make a recombinant plasmid containing the gene . 2 . bacterial transformation and selection plasmids and other dna can be introduced into bacteria , such as the harmless e. coli used in labs , in a process called transformation . during transformation , specially prepared bacterial cells are given a shock ( such as high temperature ) that encourages them to take up foreign dna . a plasmid typically contains an antibiotic resistance gene , which allows bacteria to survive in the presence of a specific antibiotic . thus , bacteria that took up the plasmid can be selected on nutrient plates containing the antibiotic . bacteria without a plasmid will die , while bacteria carrying a plasmid can live and reproduce . each surviving bacterium will give rise to a small , dot-like group , or colony , of identical bacteria that all carry the same plasmid . not all colonies will necessarily contain the right plasmid . that ’ s because , during a ligation , dna fragments don ’ t always get “ pasted ” in exactly the way we intend . instead , we must collect dna from several colonies and see whether each one contain the right plasmid . methods like restriction enzyme digestion and pcr are commonly used to check the plasmids . 3 . protein production once we have found a bacterial colony with the right plasmid , we can grow a large culture of plasmid-bearing bacteria . then , we give the bacteria a chemical signal that instructs them to make the target protein . the bacteria serve as miniature “ factories , '' churning out large amounts of protein . for instance , if our plasmid contained the human insulin gene , the bacteria would start transcribing the gene and translating the mrna to produce many molecules of human insulin protein . once the protein has been produced , the bacterial cells can be split open to release it . there are many other proteins and macromolecules floating around in bacteria besides the target protein ( e.g. , insulin ) . because of this , the target protein must be purified , or separated from the other contents of the cells by biochemical techniques . the purified protein can be used for experiments or , in the case of insulin , administered to patients . uses of dna cloning dna molecules built through cloning techniques are used for many purposes in molecular biology . a short list of examples includes : biopharmaceuticals . dna cloning can be used to make human proteins with biomedical applications , such as the insulin mentioned above . other examples of recombinant proteins include human growth hormone , which is given to patients who are unable to synthesize the hormone , and tissue plasminogen activator ( tpa ) , which is used to treat strokes and prevent blood clots . recombinant proteins like these are often made in bacteria . gene therapy . in some genetic disorders , patients lack the functional form of a particular gene . gene therapy attempts to provide a normal copy of the gene to the cells of a patient ’ s body . for example , dna cloning was used to build plasmids containing a normal version of the gene that 's nonfunctional in cystic fibrosis . when the plasmids were delivered to the lungs of cystic fibrosis patients , lung function deteriorated less quickly $ ^2 $ . gene analysis . in basic research labs , biologists often use dna cloning to build artificial , recombinant versions of genes that help them understand how normal genes in an organism function . these are just a few examples of how dna cloning is used in biology today . dna cloning is a very common technique that is used in a huge variety of molecular biology applications .
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the purified protein can be used for experiments or , in the case of insulin , administered to patients . uses of dna cloning dna molecules built through cloning techniques are used for many purposes in molecular biology . a short list of examples includes : biopharmaceuticals .
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there are the uses of dna cloning , but what are some of the disadvantages that come with this process ?
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