Question

Cure

Answer 1

Considering a cylindrical conductor of length L and area of cross-section A. For example, a wire, which is generally cylindrical in shape.

Now, when a potential difference is applied across its ends, its free electrons begin to drift towards positive terminal of the battery. Let 'v' be their average velocity.

Charge on each electron is q, so total charge which is contributing to current is N*q, where N is total number of free electrons.

Let 'n' be the number density. Then,

Hence,

Now, current is charge per unit time, therefore,

Finally, current density is current per unit area.

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