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Polarized objects have their positive and negative charges concentrated in different areas, giving them a non-symmetrical charge. | https://openstax.org/books/college-physics-2e/pages/18-section-summary |
Polar molecules have an inherent separation of charge. | https://openstax.org/books/college-physics-2e/pages/18-section-summary |
Frenchman Charles Coulomb was the first to publish the mathematical equation that describes the electrostatic force between two objects. | https://openstax.org/books/college-physics-2e/pages/18-section-summary |
Coulombâs law gives the magnitude of the force between point charges. It isF=k|q1q2|r2,F=k|q1q2|r2,whereq1q1andq2q2are two point charges separated by a distancerr, andkâ8.99Ã109N·m2/C2kâ8.99Ã109N·m2/C2 | https://openstax.org/books/college-physics-2e/pages/18-section-summary |
whereq1q1andq2q2are two point charges separated by a distancerr, andkâ8.99Ã109N·m2/C2kâ8.99Ã109N·m2/C2 | https://openstax.org/books/college-physics-2e/pages/18-section-summary |
This Coulomb force is extremely basic, since most charges are due to point-like particles. It is responsible for all electrostatic effects and underlies most macroscopic forces. | https://openstax.org/books/college-physics-2e/pages/18-section-summary |
The Coulomb force is extraordinarily strong compared with the gravitational force, another basic forceâbut unlike gravitational force it can cancel, since it can be either attractive or repulsive. | https://openstax.org/books/college-physics-2e/pages/18-section-summary |
The electrostatic force between two subatomic particles is far greater than the gravitational force between the same two particles. | https://openstax.org/books/college-physics-2e/pages/18-section-summary |
The electrostatic force field surrounding a charged object extends out into space in all directions. | https://openstax.org/books/college-physics-2e/pages/18-section-summary |
The electrostatic force exerted by a point charge on a test charge at a distancerrdepends on the charge of both charges, as well as the distance between the two. | https://openstax.org/books/college-physics-2e/pages/18-section-summary |
The electric fieldEEis defined to beE=Fq,E=Fq,whereFFis the Coulomb or electrostatic force exerted on a small positive test chargeqq.EEhas units of N/C. | https://openstax.org/books/college-physics-2e/pages/18-section-summary |
whereFFis the Coulomb or electrostatic force exerted on a small positive test chargeqq.EEhas units of N/C. | https://openstax.org/books/college-physics-2e/pages/18-section-summary |
The magnitude of the electric fieldEEcreated by a point chargeQQisE=k|Q|r2.E=k|Q|r2.whererris the distance fromQQ. The electric fieldEEis a vector and fields due to multiple charges add like vectors. | https://openstax.org/books/college-physics-2e/pages/18-section-summary |
whererris the distance fromQQ. The electric fieldEEis a vector and fields due to multiple charges add like vectors. | https://openstax.org/books/college-physics-2e/pages/18-section-summary |
Drawings of electric field lines are useful visual tools. The properties of electric field lines for any charge distribution are that: | https://openstax.org/books/college-physics-2e/pages/18-section-summary |
Field lines must begin on positive charges and terminate on negative charges, or at infinity in the hypothetical case of isolated charges. | https://openstax.org/books/college-physics-2e/pages/18-section-summary |
The number of field lines leaving a positive charge or entering a negative charge is proportional to the magnitude of the charge. | https://openstax.org/books/college-physics-2e/pages/18-section-summary |
The strength of the field is proportional to the closeness of the field linesâmore precisely, it is proportional to the number of lines per unit area perpendicular to the lines. | https://openstax.org/books/college-physics-2e/pages/18-section-summary |
The direction of the electric field is tangent to the field line at any point in space. | https://openstax.org/books/college-physics-2e/pages/18-section-summary |
Field lines can never cross. | https://openstax.org/books/college-physics-2e/pages/18-section-summary |
Many molecules in living organisms, such as DNA, carry a charge. | https://openstax.org/books/college-physics-2e/pages/18-section-summary |
An uneven distribution of the positive and negative charges within a polar molecule produces a dipole. | https://openstax.org/books/college-physics-2e/pages/18-section-summary |
The effect of a Coulomb field generated by a charged object may be reduced or blocked by other nearby charged objects. | https://openstax.org/books/college-physics-2e/pages/18-section-summary |
Biological systems contain water, and because water molecules are polar, they have a strong effect on other molecules in living systems. | https://openstax.org/books/college-physics-2e/pages/18-section-summary |
A conductor allows free charges to move about within it. | https://openstax.org/books/college-physics-2e/pages/18-section-summary |
The electrical forces around a conductor will cause free charges to move around inside the conductor until static equilibrium is reached. | https://openstax.org/books/college-physics-2e/pages/18-section-summary |
Any excess charge will collect along the surface of a conductor. | https://openstax.org/books/college-physics-2e/pages/18-section-summary |
Conductors with sharp corners or points will collect more charge at those points. | https://openstax.org/books/college-physics-2e/pages/18-section-summary |
A lightning rod is a conductor with sharply pointed ends that collect excess charge on the building caused by an electrical storm and allow it to dissipate back into the air. | https://openstax.org/books/college-physics-2e/pages/18-section-summary |
Electrical storms result when the electrical field of Earthâs surface in certain locations becomes more strongly charged, due to changes in the insulating effect of the air. | https://openstax.org/books/college-physics-2e/pages/18-section-summary |
A Faraday cage acts like a shield around an object, preventing electric charge from penetrating inside. | https://openstax.org/books/college-physics-2e/pages/18-section-summary |
Electrostatics is the study of electric fields in static equilibrium. | https://openstax.org/books/college-physics-2e/pages/18-section-summary |
In addition to research using equipment such as a Van de Graaff generator, many practical applications of electrostatics exist, including photocopiers, laser printers, ink-jet printers and electrostatic air filters. | https://openstax.org/books/college-physics-2e/pages/18-section-summary |
capacitance : amount of charge stored per unit volt | https://openstax.org/books/college-physics-2e/pages/19-glossary |
capacitor : a device that stores electric charge | https://openstax.org/books/college-physics-2e/pages/19-glossary |
defibrillator : a machine used to provide an electrical shock to a heart attack victim's heart in order to restore the heart's normal rhythmic pattern | https://openstax.org/books/college-physics-2e/pages/19-glossary |
dielectric : an insulating material | https://openstax.org/books/college-physics-2e/pages/19-glossary |
dielectric strength : the maximum electric field above which an insulating material begins to break down and conduct | https://openstax.org/books/college-physics-2e/pages/19-glossary |
electric potential : potential energy per unit charge | https://openstax.org/books/college-physics-2e/pages/19-glossary |
electron volt : the energy given to a fundamental charge accelerated through a potential difference of one volt | https://openstax.org/books/college-physics-2e/pages/19-glossary |
equipotential line : a line along which the electric potential is constant | https://openstax.org/books/college-physics-2e/pages/19-glossary |
grounding : fixing a conductor at zero volts by connecting it to the earth or ground | https://openstax.org/books/college-physics-2e/pages/19-glossary |
mechanical energy : sum of the kinetic energy and potential energy of a system; this sum is a constant | https://openstax.org/books/college-physics-2e/pages/19-glossary |
parallel plate capacitor : two identical conducting plates separated by a distance | https://openstax.org/books/college-physics-2e/pages/19-glossary |
polar molecule : a molecule with inherent separation of charge | https://openstax.org/books/college-physics-2e/pages/19-glossary |
potential difference (or voltage) : change in potential energy of a charge moved from one point to another, divided by the charge; units of potential difference are joules per coulomb, known as volt | https://openstax.org/books/college-physics-2e/pages/19-glossary |
scalar : physical quantity with magnitude but no direction | https://openstax.org/books/college-physics-2e/pages/19-glossary |
vector : physical quantity with both magnitude and direction | https://openstax.org/books/college-physics-2e/pages/19-glossary |
Electric potential is potential energy per unit charge. | https://openstax.org/books/college-physics-2e/pages/19-section-summary |
The potential difference between points A and B,VBâVAVBâVA, defined to be the change in potential energy of a chargeqqmoved from A to B, is equal to the change in potential energy divided by the charge, Potential difference is commonly called voltage, represented by the symbolÎVÎV.ÎV=ÎPEqand ÎPE =qÎV.ÎV=ÎPE... | https://openstax.org/books/college-physics-2e/pages/19-section-summary |
An electron volt is the energy given to a fundamental charge accelerated through a potential difference of 1 V. In equation form,1 eV=1.60Ã10â19C1 V=1.60Ã10â19C1 J/C=1.60Ã10â19J.1 eV=1.60Ã10â19C1 V=1.60Ã10â19C1 J/C=1.60Ã10â19J. | https://openstax.org/books/college-physics-2e/pages/19-section-summary |
Mechanical energy is the sum of the kinetic energy and potential energy of a system, that is,KE+PE.KE+PE.This sum is a constant. | https://openstax.org/books/college-physics-2e/pages/19-section-summary |
The voltage between points A and B isVAB=EdE=VABd(uniformE- field only),VAB=EdE=VABd(uniformE- field only),whereddis the distance from A to B, or the distance between the plates. | https://openstax.org/books/college-physics-2e/pages/19-section-summary |
In equation form, the general relationship between voltage and electric field isE=âÎVÎs,E=âÎVÎs,whereÎsÎsis the distance over which the change in potential,ÎVÎV, takes place. The minus sign tells us thatEEpoints in the direction of decreasing potential.) The electric field is said to be thegradient(as in gr... | https://openstax.org/books/college-physics-2e/pages/19-section-summary |
Electric potential of a point charge isV=kQ/rV=kQ/r. | https://openstax.org/books/college-physics-2e/pages/19-section-summary |
Electric potential is a scalar, and electric field is a vector. Addition of voltages as numbers gives the voltage due to a combination of point charges, whereas addition of individual fields as vectors gives the total electric field. | https://openstax.org/books/college-physics-2e/pages/19-section-summary |
An equipotential line is a line along which the electric potential is constant. | https://openstax.org/books/college-physics-2e/pages/19-section-summary |
An equipotential surface is a three-dimensional version of equipotential lines. | https://openstax.org/books/college-physics-2e/pages/19-section-summary |
Equipotential lines are always perpendicular to electric field lines. | https://openstax.org/books/college-physics-2e/pages/19-section-summary |
The process by which a conductor can be fixed at zero volts by connecting it to the earth with a good conductor is called grounding. | https://openstax.org/books/college-physics-2e/pages/19-section-summary |
Acapacitoris a device used to store charge. | https://openstax.org/books/college-physics-2e/pages/19-section-summary |
The amount of chargeQQa capacitor can store depends on two major factorsâthe voltage applied and the capacitorâs physical characteristics, such as its size. | https://openstax.org/books/college-physics-2e/pages/19-section-summary |
The capacitanceCCis the amount of charge stored per volt,orC=QV.C=QV. | https://openstax.org/books/college-physics-2e/pages/19-section-summary |
The capacitance of a parallel plate capacitor isC=ε0AdC=ε0Ad, when the plates are separated by air or free space.ε0ε0is called the permittivity of free space. | https://openstax.org/books/college-physics-2e/pages/19-section-summary |
A parallel plate capacitor with a dielectric between its plates has a capacitance given byC=κε0Ad,C=κε0Ad,whereκκis the dielectric constant of the material. | https://openstax.org/books/college-physics-2e/pages/19-section-summary |
The maximum electric field strength above which an insulating material begins to break down and conduct is called dielectric strength. | https://openstax.org/books/college-physics-2e/pages/19-section-summary |
Total capacitance in series1CS=1C1+1C2+1C3+...1CS=1C1+1C2+1C3+... | https://openstax.org/books/college-physics-2e/pages/19-section-summary |
Total capacitance in parallelCp=C1+C2+C3+...Cp=C1+C2+C3+... | https://openstax.org/books/college-physics-2e/pages/19-section-summary |
If a circuit contains a combination of capacitors in series and parallel, identify series and parallel parts, compute their capacitances, and then find the total. | https://openstax.org/books/college-physics-2e/pages/19-section-summary |
Capacitors are used in a variety of devices, including defibrillators, microelectronics such as calculators, and flash lamps, to supply energy. | https://openstax.org/books/college-physics-2e/pages/19-section-summary |
The energy stored in a capacitor can be expressed in three ways:Ecap=QV2=CV22=Q22C,Ecap=QV2=CV22=Q22C,whereQQis the charge,VVis the voltage, andCCis the capacitance of the capacitor. The energy is in joules when the charge is in coulombs, voltage is in volts, and capacitance is in farads. | https://openstax.org/books/college-physics-2e/pages/19-section-summary |
AC current : current that fluctuates sinusoidally with time, expressed asI = I0sin 2Ïft, whereIis the current at timet, I0is the peak current, andfis the frequency in hertz | https://openstax.org/books/college-physics-2e/pages/20-glossary |
AC voltage : voltage that fluctuates sinusoidally with time, expressed asV = V0sin 2Ïft, whereVis the voltage at timet, V0is the peak voltage, andfis the frequency in hertz | https://openstax.org/books/college-physics-2e/pages/20-glossary |
alternating current : (AC) the flow of electric charge that periodically reverses direction | https://openstax.org/books/college-physics-2e/pages/20-glossary |
ampere : (amp) the SI unit for current; 1 A = 1 C/s | https://openstax.org/books/college-physics-2e/pages/20-glossary |
bioelectricity : electrical effects in and created by biological systems | https://openstax.org/books/college-physics-2e/pages/20-glossary |
direct current : (DC) the flow of electric charge in only one direction | https://openstax.org/books/college-physics-2e/pages/20-glossary |
drift velocity : the average velocity at which free charges flow in response to an electric field | https://openstax.org/books/college-physics-2e/pages/20-glossary |
electric current : the rate at which charge flows,I= ÎQ/Ît | https://openstax.org/books/college-physics-2e/pages/20-glossary |
electric power : the rate at which electrical energy is supplied by a source or dissipated by a device; it is the product of current times voltage | https://openstax.org/books/college-physics-2e/pages/20-glossary |
electrocardiogram (ECG) : usually abbreviated ECG, a record of voltages created by depolarization and repolarization, especially in the heart | https://openstax.org/books/college-physics-2e/pages/20-glossary |
microshock sensitive : a condition in which a personâs skin resistance is bypassed, possibly by a medical procedure, rendering the person vulnerable to electrical shock at currents about 1/1000 the normally required level | https://openstax.org/books/college-physics-2e/pages/20-glossary |
nerve conduction : the transport of electrical signals by nerve cells | https://openstax.org/books/college-physics-2e/pages/20-glossary |
ohm : the unit of resistance, given by 1Ω = 1 V/A | https://openstax.org/books/college-physics-2e/pages/20-glossary |
Ohmâs law : an empirical relation stating that the currentIis proportional to the potential differenceV,â V; it is often written asI = V/R, whereRis the resistance | https://openstax.org/books/college-physics-2e/pages/20-glossary |
ohmic : a type of a material for which Ohm's law is valid | https://openstax.org/books/college-physics-2e/pages/20-glossary |
resistance : the electric property that impedes current; for ohmic materials, it is the ratio of voltage to current,R = V/I | https://openstax.org/books/college-physics-2e/pages/20-glossary |
resistivity : an intrinsic property of a material, independent of its shape or size, directly proportional to the resistance, denoted byÏ | https://openstax.org/books/college-physics-2e/pages/20-glossary |
rms current : the root mean square of the current,Irms=I0/2Irms=I0/2, whereI0is the peak current, in an AC system | https://openstax.org/books/college-physics-2e/pages/20-glossary |
rms voltage : the root mean square of the voltage,Vrms=V0/2Vrms=V0/2, whereV0is the peak voltage, in an AC system | https://openstax.org/books/college-physics-2e/pages/20-glossary |
semipermeable : property of a membrane that allows only certain types of ions to cross it | https://openstax.org/books/college-physics-2e/pages/20-glossary |
shock hazard : when electric current passes through a person | https://openstax.org/books/college-physics-2e/pages/20-glossary |
short circuit : also known as a âshort,â a low-resistance path between terminals of a voltage source | https://openstax.org/books/college-physics-2e/pages/20-glossary |
simple circuit : a circuit with a single voltage source and a single resistor | https://openstax.org/books/college-physics-2e/pages/20-glossary |
temperature coefficient of resistivity : an empirical quantity, denoted byα, which describes the change in resistance or resistivity of a material with temperature | https://openstax.org/books/college-physics-2e/pages/20-glossary |
thermal hazard : a hazard in which electric current causes undesired thermal effects | https://openstax.org/books/college-physics-2e/pages/20-glossary |
Electric currentIIis the rate at which charge flows, given byI=ÎQÎt,I=ÎQÎt,whereÎQÎQis the amount of charge passing through an area in timeÎtÎt. | https://openstax.org/books/college-physics-2e/pages/20-section-summary |
The direction of conventional current is taken as the direction in which positive charge moves. | https://openstax.org/books/college-physics-2e/pages/20-section-summary |
The SI unit for current is the ampere (A), where1 A=1 C/s.1 A=1 C/s. | https://openstax.org/books/college-physics-2e/pages/20-section-summary |
Current is the flow of free charges, such as electrons and ions. | https://openstax.org/books/college-physics-2e/pages/20-section-summary |
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