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Wikipedia defines charge as the fundamental property of forms of matter that exhibits electrostatic attraction or repulsion in the presence of other matter.Strictly speaking, while defining an electric current, will it be right to define it as the "flow of charges"?

user161940
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2 Answers2

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Yes, that's the definition. More precisely, current is the amount of charge (measured in Coulomb) flowing past a cross section per time interval (measured in seconds).

Steeven
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    Will it be better to say "flow of charged particles" rather than "flow of charges"?(Amount of charge sounds much better to me than saying "charges") – user161940 Sep 23 '15 at 15:26
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    I said "amount of charge", since that is what it is. Not sure what you mean by this comment, @user161940. Current is not the number of charged particles passing per second, it is the amount of charge (measured in Coulomb) passing per second. This you could consider a flow, yes, but a flow is a pretty fluffy term and not very good for definitions. – Steeven Sep 23 '15 at 20:06
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Yes, that is correct in a very strict and narrow sense. You can totally use the term "charge" to mean a particle which holds a certain fundamental electric charge.

In a much broader sense, please notice that a current can be said to flow across a capacitor (a break in a circuit!) even when charges cannot move between the terminals of the capacitor. Microscopically, some charges of opposite sign "build up" on the terminals in order to make this possible. Furthermore, the "changing electric field" between these terminals has all of the magnetic effects that the current itself has on the outside world, so magnetically it appears as if there is no break in the current at all.

In addition, sometimes a current will come based on the reorientation of dipoles: each one is just a $+$ charge clinging to a $-$ charge of the same magnitude, but if a region of polarizable insulator goes from having all of its dipoles randomly directed to having them all pointed in one direction, one side will appear to have a $+$ charge and the opposite side will appear to have a $-$ charge: even though we know for a fact that no particles containing charges have moved from the one side to the other, we can speak of a "current" that has flowed from one side to the other.

It also builds up the misapprehension that the velocity with which an electric signal travels is approximately the drift velocity of the electrons themselves. Actually it is kind of like transferring the "kick" of one ball to another in a Newton's cradle, the slow-moving electrons already "kick" the electrons ahead of them forward.

So, there are these "broader" definitions which don't quite work that way. A current is basically anything which can transmit a net charge from point A to point B, or possibly anything which creates a magnetic field that curls around it.

CR Drost
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