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| {{distinguish2|amperemeter, another term for the [[ammeter]]}}
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| The '''ampere-meter''' which has the symbol '''A m''' or '''A·m''' is the [[SI]] unit for pole strength in a [[magnet]].
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| ==Derivation==
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| [[Einstein]] proved that a [[magnetic field]] is the [[theory of relativity|relativistic]] part of an [[electric field]]. This means that while an electric field acts between [[electric charge|charges]], a magnetic field acts between ''moving'' charges (as a charge moves through space more quickly and through time more slowly, its [[electromagnetism|electromagnetic force]] becomes more magnetic and less electric). Therefore, the pole strength is the product of charge and [[velocity]].
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| <math>1~\mathrm{A \cdot m} = 1~\mathrm{C} \cdot \frac{\mathrm{m}}{\mathrm{s}}</math> | |
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| ==Usefulness==
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| Few calculations actually involve the strength of a pole in ampere-meters because a [[magnetic monopole|single magnetic pole]] has never been isolated. Magnets are [[dipole]]s which require more complicated calculations than monopoles. However, the strength of a magnetic field is measured in [[Tesla (unit)|teslas]] and one tesla is one [[Newton (unit)|newton]] per ampere-meter which confirms that the unit for pole strength is indeed the ampere-meter.
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| ==Misconceptions==
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| The idea that magnetic forces act on moving charges is clear in an [[electromagnet]] but not obvious in a [[permanent magnet]]. In fact, all substances have charges moving in them all of the time, one of the difficulties in reaching [[absolute zero]]. In most substances, all of the magnetic fields produced by this motion cancel each other out, but magnetic substances have more proper alignment. At the microscopic level, many molecules are magnets — [[hydrogen fluoride]] for example is a dipole. [[Polarity (physics)|Polarity]] is most often expressed in terms of [[electronegativity]] but the strength of its poles could be expressed in ampere-meters as well.
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| ==References==
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| *[http://www.phys.unsw.edu.au/einsteinlight/jw/module2_FEB.htm The electric and magnetic forces between moving charges]
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| *[http://www.qsl.net/g4cnn/units/units.htm Units in electricity and magnetism]
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| [[Category:SI derived units]]
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| [[id:Amper-meter]]
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Revision as of 22:33, 7 February 2014
Andrew Berryhill is what his wife enjoys to call him and he totally digs that title. Office supervising is my profession. Playing badminton is a factor that he is totally addicted to. Alaska is where he's usually been residing.
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