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Ampereâs law : the physical law that states that the magnetic field around an electric current is proportional to the current; each segment of current produces a magnetic field like that of a long straight wire, and the total field of any shape current is the vector sum of the fields due to each segment | https://openstax.org/books/college-physics-2e/pages/22-glossary |
B-field : another term for magnetic field | https://openstax.org/books/college-physics-2e/pages/22-glossary |
Biot-Savart law : a physical law that describes the magnetic field generated by an electric current in terms of a specific equation | https://openstax.org/books/college-physics-2e/pages/22-glossary |
Curie temperature : the temperature above which a ferromagnetic material cannot be magnetized | https://openstax.org/books/college-physics-2e/pages/22-glossary |
direction of magnetic field lines : the direction that the north end of a compass needle points | https://openstax.org/books/college-physics-2e/pages/22-glossary |
domains : regions within a material that behave like small bar magnets | https://openstax.org/books/college-physics-2e/pages/22-glossary |
electromagnet : an object that is temporarily magnetic when an electrical current is passed through it | https://openstax.org/books/college-physics-2e/pages/22-glossary |
electromagnetism : the use of electrical currents to induce magnetism | https://openstax.org/books/college-physics-2e/pages/22-glossary |
ferromagnetic : materials, such as iron, cobalt, nickel, and gadolinium, that exhibit strong magnetic effects | https://openstax.org/books/college-physics-2e/pages/22-glossary |
gauss : G, the unit of the magnetic field strength;1 G=10â4T1 G=10â4T | https://openstax.org/books/college-physics-2e/pages/22-glossary |
Hall effect : the creation of voltage across a current-carrying conductor by a magnetic field | https://openstax.org/books/college-physics-2e/pages/22-glossary |
Hall emf : the electromotive force created by a current-carrying conductor by a magnetic field,ε=Blvε=Blv | https://openstax.org/books/college-physics-2e/pages/22-glossary |
Lorentz force : the force on a charge moving in a magnetic field | https://openstax.org/books/college-physics-2e/pages/22-glossary |
magnetic field : the representation of magnetic forces | https://openstax.org/books/college-physics-2e/pages/22-glossary |
magnetic field lines : the pictorial representation of the strength and the direction of a magnetic field | https://openstax.org/books/college-physics-2e/pages/22-glossary |
magnetic field strength (magnitude) produced by a long straight current-carrying wire : defined asB=μ0I2ÏrB=μ0I2Ïr, whereIIis the current,rris the shortest distance to the wire, andμ0μ0is the permeability of free space | https://openstax.org/books/college-physics-2e/pages/22-glossary |
magnetic field strength at the center of a circular loop : defined asB=μ0I2RB=μ0I2RwhereRRis the radius of the loop | https://openstax.org/books/college-physics-2e/pages/22-glossary |
magnetic field strength inside a solenoid : defined asB=μ0nIB=μ0nIwherennis the number of loops per unit length of the solenoid(n=N/l(n=N/l, withNNbeing the number of loops andllthe length) | https://openstax.org/books/college-physics-2e/pages/22-glossary |
magnetic force : the force on a charge produced by its motion through a magnetic field; the Lorentz force | https://openstax.org/books/college-physics-2e/pages/22-glossary |
magnetic monopoles : an isolated magnetic pole; a south pole without a north pole, or vice versa (no magnetic monopole has ever been observed) | https://openstax.org/books/college-physics-2e/pages/22-glossary |
magnetic resonance imaging (MRI) : a medical imaging technique that uses magnetic fields create detailed images of internal tissues and organs | https://openstax.org/books/college-physics-2e/pages/22-glossary |
magnetized : to be turned into a magnet; to be induced to be magnetic | https://openstax.org/books/college-physics-2e/pages/22-glossary |
magnetocardiogram (MCG) : a recording of the heartâs magnetic field as it beats | https://openstax.org/books/college-physics-2e/pages/22-glossary |
magnetoencephalogram (MEG) : a measurement of the brainâs magnetic field | https://openstax.org/books/college-physics-2e/pages/22-glossary |
Maxwellâs equations : a set of four equations that describe electromagnetic phenomena | https://openstax.org/books/college-physics-2e/pages/22-glossary |
meter : common application of magnetic torque on a current-carrying loop that is very similar in construction to a motor; by design, the torque is proportional toIIand notθθ, so the needle deflection is proportional to the current | https://openstax.org/books/college-physics-2e/pages/22-glossary |
motor : loop of wire in a magnetic field; when current is passed through the loops, the magnetic field exerts torque on the loops, which rotates a shaft; electrical energy is converted to mechanical work in the process | https://openstax.org/books/college-physics-2e/pages/22-glossary |
north magnetic pole : the end or the side of a magnet that is attracted toward Earthâs geographic north pole | https://openstax.org/books/college-physics-2e/pages/22-glossary |
nuclear magnetic resonance (NMR) : a phenomenon in which an externally applied magnetic field interacts with the nuclei of certain atoms | https://openstax.org/books/college-physics-2e/pages/22-glossary |
permeability of free space : the measure of the ability of a material, in this case free space, to support a magnetic field; the constantμ0=4ÏÃ10â7Tâm/Aμ0=4ÏÃ10â7Tâm/A | https://openstax.org/books/college-physics-2e/pages/22-glossary |
right hand rule 1 (RHR-1) : the rule to determine the direction of the magnetic force on a positive moving charge: when the thumb of the right hand points in the direction of the chargeâs velocityvvand the fingers point in the direction of the magnetic fieldBB, then the force on the charge is perpendicular and away f... | https://openstax.org/books/college-physics-2e/pages/22-glossary |
right hand rule 2 (RHR-2) : a rule to determine the direction of the magnetic field induced by a current-carrying wire: Point the thumb of the right hand in the direction of current, and the fingers curl in the direction of the magnetic field loops | https://openstax.org/books/college-physics-2e/pages/22-glossary |
solenoid : a thin wire wound into a coil that produces a magnetic field when an electric current is passed through it | https://openstax.org/books/college-physics-2e/pages/22-glossary |
south magnetic pole : the end or the side of a magnet that is attracted toward Earthâs geographic south pole | https://openstax.org/books/college-physics-2e/pages/22-glossary |
tesla : T, the SI unit of the magnetic field strength;1 T=1 NAâm1 T=1 NAâm | https://openstax.org/books/college-physics-2e/pages/22-glossary |
Magnetism is a subject that includes the properties of magnets, the effect of the magnetic force on moving charges and currents, and the creation of magnetic fields by currents. | https://openstax.org/books/college-physics-2e/pages/22-section-summary |
There are two types of magnetic poles, called the north magnetic pole and south magnetic pole. | https://openstax.org/books/college-physics-2e/pages/22-section-summary |
North magnetic poles are those that are attracted toward the Earthâs geographic north pole. | https://openstax.org/books/college-physics-2e/pages/22-section-summary |
Like poles repel and unlike poles attract. | https://openstax.org/books/college-physics-2e/pages/22-section-summary |
Magnetic poles always occur in pairs of north and southâit is not possible to isolate north and south poles. | https://openstax.org/books/college-physics-2e/pages/22-section-summary |
Magnetic poles always occur in pairs of north and southâit is not possible to isolate north and south poles. | https://openstax.org/books/college-physics-2e/pages/22-section-summary |
All magnetism is created by electric current. | https://openstax.org/books/college-physics-2e/pages/22-section-summary |
Ferromagnetic materials, such as iron, are those that exhibit strong magnetic effects. | https://openstax.org/books/college-physics-2e/pages/22-section-summary |
The atoms in ferromagnetic materials act like small magnets (due to currents within the atoms) and can be aligned, usually in millimeter-sized regions called domains. | https://openstax.org/books/college-physics-2e/pages/22-section-summary |
Domains can grow and align on a larger scale, producing permanent magnets. Such a material is magnetized, or induced to be magnetic. | https://openstax.org/books/college-physics-2e/pages/22-section-summary |
Above a materialâs Curie temperature, thermal agitation destroys the alignment of atoms, and ferromagnetism disappears. | https://openstax.org/books/college-physics-2e/pages/22-section-summary |
Electromagnets employ electric currents to make magnetic fields, often aided by induced fields in ferromagnetic materials. | https://openstax.org/books/college-physics-2e/pages/22-section-summary |
Magnetic fields can be pictorially represented by magnetic field lines, the properties of which are as follows: | https://openstax.org/books/college-physics-2e/pages/22-section-summary |
The field is tangent to the magnetic field line. | https://openstax.org/books/college-physics-2e/pages/22-section-summary |
Field strength is proportional to the line density. | https://openstax.org/books/college-physics-2e/pages/22-section-summary |
Field lines cannot cross. | https://openstax.org/books/college-physics-2e/pages/22-section-summary |
Field lines are continuous loops. | https://openstax.org/books/college-physics-2e/pages/22-section-summary |
Magnetic fields exert a force on a moving chargeq, the magnitude of which isF=qvBsinθ,F=qvBsinθ,whereθθis the angle between the directions ofvvandBB. | https://openstax.org/books/college-physics-2e/pages/22-section-summary |
The SI unit for magnetic field strengthBBis the tesla (T), which is related to other units by1 T=1 NCâm/s=1 NAâm.1 T=1 NCâm/s=1 NAâm. | https://openstax.org/books/college-physics-2e/pages/22-section-summary |
Thedirectionof the force on a moving charge is given by right hand rule 1 (RHR-1): Point the thumb of the right hand in the direction ofvv, the fingers in the direction ofBB, and a perpendicular to the palm points in the direction ofFF. | https://openstax.org/books/college-physics-2e/pages/22-section-summary |
The force is perpendicular to the plane formed byvvandBB. Since the force is zero ifvvis parallel toBB, charged particles often follow magnetic field lines rather than cross them. | https://openstax.org/books/college-physics-2e/pages/22-section-summary |
Magnetic force can supply centripetal force and cause a charged particle to move in a circular path of radiusr=mvqB,r=mvqB,wherevvis the component of the velocity perpendicular toBBfor a charged particle with massmmand chargeqq. | https://openstax.org/books/college-physics-2e/pages/22-section-summary |
The Hall effect is the creation of voltageεε, known as the Hall emf, across a current-carrying conductor by a magnetic field. | https://openstax.org/books/college-physics-2e/pages/22-section-summary |
The Hall emf is given byε=Blv(B,v,andl,mutually perpendicular)ε=Blv(B,v,andl,mutually perpendicular)for a conductor of widthllthrough which charges move at a speedvv. | https://openstax.org/books/college-physics-2e/pages/22-section-summary |
The magnetic force on current-carrying conductors is given byF=IlBsinθ,F=IlBsinθ,whereIIis the current,llis the length of a straight conductor in a uniform magnetic fieldBB, andθθis the angle betweenIIandBB. The force follows RHR-1 with the thumb in the direction ofII. | https://openstax.org/books/college-physics-2e/pages/22-section-summary |
The torqueÏÏon a current-carrying loop of any shape in a uniform magnetic field. isÏ=NIABsinθ,Ï=NIABsinθ,whereNNis the number of turns,IIis the current,AAis the area of the loop,BBis the magnetic field strength, andθθis the angle between the perpendicular to the loop and the magnetic field. | https://openstax.org/books/college-physics-2e/pages/22-section-summary |
The strength of the magnetic field created by current in a long straight wire is given byB=μ0I2Ïr(long straight wire),B=μ0I2Ïr(long straight wire),whereIIis the current,rris the shortest distance to the wire, and the constantμ0=4ÏÃ10â7Tâm/Aμ0=4ÏÃ10â7Tâm/Ais the permeability of free space. | https://openstax.org/books/college-physics-2e/pages/22-section-summary |
The direction of the magnetic field created by a long straight wire is given by right hand rule 2 (RHR-2):Point the thumb of the right hand in the direction of current, and the fingers curl in the direction of the magnetic field loopscreated by it. | https://openstax.org/books/college-physics-2e/pages/22-section-summary |
The magnetic field created by current following any path is the sum (or integral) of the fields due to segments along the path (magnitude and direction as for a straight wire), resulting in a general relationship between current and field known as Ampereâs law. | https://openstax.org/books/college-physics-2e/pages/22-section-summary |
The magnetic field strength at the center of a circular loop is given byB=μ0I2R(at center of loop),B=μ0I2R(at center of loop),whereRRis the radius of the loop. This equation becomesB=μ0nI/(2R)B=μ0nI/(2R)for a flat coil ofNNloops. RHR-2 gives the direction of the field about the loop. A long coil is called a solenoi... | https://openstax.org/books/college-physics-2e/pages/22-section-summary |
The magnetic field strength inside a solenoid isB=μ0nI(inside a solenoid),B=μ0nI(inside a solenoid),wherennis the number of loops per unit length of the solenoid. The field inside is very uniform in magnitude and direction. | https://openstax.org/books/college-physics-2e/pages/22-section-summary |
The force between two parallel currentsI1I1andI2I2, separated by a distancerr, has a magnitude per unit length given byFl=μ0I1I22Ïr.Fl=μ0I1I22Ïr. | https://openstax.org/books/college-physics-2e/pages/22-section-summary |
The force is attractive if the currents are in the same direction, repulsive if they are in opposite directions. | https://openstax.org/books/college-physics-2e/pages/22-section-summary |
Crossed (perpendicular) electric and magnetic fields act as a velocity filter, giving equal and opposite forces on any charge with velocity perpendicular to the fields and of magnitudev=EB.v=EB. | https://openstax.org/books/college-physics-2e/pages/22-section-summary |
back emf : the emf generated by a running motor, because it consists of a coil turning in a magnetic field; it opposes the voltage powering the motor | https://openstax.org/books/college-physics-2e/pages/23-glossary |
capacitive reactance : the opposition of a capacitor to a change in current; calculated byXC=12ÏfCXC=12ÏfC | https://openstax.org/books/college-physics-2e/pages/23-glossary |
characteristic time constant : denoted byÏÏ, of a particular seriesRLcircuit is calculated byÏ=LRÏ=LR, whereLLis the inductance andRRis the resistance | https://openstax.org/books/college-physics-2e/pages/23-glossary |
eddy current : a current loop in a conductor caused by motional emf | https://openstax.org/books/college-physics-2e/pages/23-glossary |
electric generator : a device for converting mechanical work into electric energy; it induces an emf by rotating a coil in a magnetic field | https://openstax.org/books/college-physics-2e/pages/23-glossary |
electromagnetic induction : the process of inducing an emf (voltage) with a change in magnetic flux | https://openstax.org/books/college-physics-2e/pages/23-glossary |
emf induced in a generator coil : emf=NABÏsinÏtemf=NABÏsinÏt, whereAAis the area of anNN-turn coil rotated at a constant angular velocityÏÏin a uniform magnetic fieldBB, over a period of timett | https://openstax.org/books/college-physics-2e/pages/23-glossary |
energy stored in an inductor : self-explanatory; calculated byEind=12LI2Eind=12LI2 | https://openstax.org/books/college-physics-2e/pages/23-glossary |
Faradayâs law of induction : the means of calculating the emf in a coil due to changing magnetic flux, given byemf=âNÎΦÎtemf=âNÎΦÎt | https://openstax.org/books/college-physics-2e/pages/23-glossary |
henry : the unit of inductance;1H=1멉s1H=1멉s | https://openstax.org/books/college-physics-2e/pages/23-glossary |
impedance : the AC analogue to resistance in a DC circuit; it is the combined effect of resistance, inductive reactance, and capacitive reactance in the formZ=R2+(XLâXC)2Z=R2+(XLâXC)2 | https://openstax.org/books/college-physics-2e/pages/23-glossary |
inductance : a property of a device describing how efficient it is at inducing emf in another device | https://openstax.org/books/college-physics-2e/pages/23-glossary |
induction : (magnetic induction) the creation of emfs and hence currents by magnetic fields | https://openstax.org/books/college-physics-2e/pages/23-glossary |
inductive reactance : the opposition of an inductor to a change in current; calculated byXL=2ÏfLXL=2ÏfL | https://openstax.org/books/college-physics-2e/pages/23-glossary |
inductor : a device that exhibits significant self-inductance | https://openstax.org/books/college-physics-2e/pages/23-glossary |
Lenzâs law : the minus sign in Faradayâs law, signifying that the emf induced in a coil opposes the change in magnetic flux | https://openstax.org/books/college-physics-2e/pages/23-glossary |
magnetic damping : the drag produced by eddy currents | https://openstax.org/books/college-physics-2e/pages/23-glossary |
magnetic flux : the amount of magnetic field going through a particular area, calculated withΦ=BAcosθΦ=BAcosθwhereBBis the magnetic field strength over an areaAAat an angleθθwith the perpendicular to the area | https://openstax.org/books/college-physics-2e/pages/23-glossary |
mutual inductance : how effective a pair of devices are at inducing emfs in each other | https://openstax.org/books/college-physics-2e/pages/23-glossary |
peak emf : emf0=NABÏemf0=NABÏ | https://openstax.org/books/college-physics-2e/pages/23-glossary |
phase angle : denoted byÏÏ, the amount by which the voltage and current are out of phase with each other in a circuit | https://openstax.org/books/college-physics-2e/pages/23-glossary |
power factor : the amount by which the power delivered in the circuit is less than the theoretical maximum of the circuit due to voltage and current being out of phase; calculated bycosÏcosÏ | https://openstax.org/books/college-physics-2e/pages/23-glossary |
resonant frequency : the frequency at which the impedance in a circuit is at a minimum, and also the frequency at which the circuit would oscillate if not driven by a voltage source; calculated byf0=12ÏLCf0=12ÏLC | https://openstax.org/books/college-physics-2e/pages/23-glossary |
self-inductance : how effective a device is at inducing emf in itself | https://openstax.org/books/college-physics-2e/pages/23-glossary |
shock hazard : the term for electrical hazards due to current passing through a human | https://openstax.org/books/college-physics-2e/pages/23-glossary |
step-down transformer : a transformer that decreases voltage | https://openstax.org/books/college-physics-2e/pages/23-glossary |
step-up transformer : a transformer that increases voltage | https://openstax.org/books/college-physics-2e/pages/23-glossary |
thermal hazard : the term for electrical hazards due to overheating | https://openstax.org/books/college-physics-2e/pages/23-glossary |
three-wire system : the wiring system used at present for safety reasons, with live, neutral, and ground wires | https://openstax.org/books/college-physics-2e/pages/23-glossary |
transformer : a device that transforms voltages from one value to another using induction | https://openstax.org/books/college-physics-2e/pages/23-glossary |
transformer equation : the equation showing that the ratio of the secondary to primary voltages in a transformer equals the ratio of the number of loops in their coils;VsVp=NsNpVsVp=NsNp | https://openstax.org/books/college-physics-2e/pages/23-glossary |
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