Electric Current and Its Related Concepts

Electric current is defined as the amount of electric charges flowing through any cross-section of a conductor per unit time.

\[I=\frac{\text{Total charge flowing (Q)}}{\text{Time taken (t)}}\]

\[I=\frac{Q}{t}\]

The S.I. unit of current is ampere (A)

Electric current through a conductor is said to be one ampere if charge of one coulomb flows through any cross-section of the conductor in one second.

\[1\mathrm{~ampere~(A)}=\frac{1\mathrm{~coulomb~(C)}}{1\mathrm{~second~(s)}}=1\mathrm{~C~s}^{-1}\]

It is defined as the velocity with which the free electrons are drifted towards the positive terminal under the effect of the applied electric field.

• The drift velocity of electrons is given by \[v_d=\frac{eE\tau}{m}\]

It is defined as the magnitude of the drift velocity of the charge carriers per unit electric field.

\[\mu=\frac{v_d}{E}=\frac{e\tau}{m}\]

The S.I. unit of mobility is \[\mathrm{m^{2}s^{-1}~V^{-1}}\] or \[\mathrm{ms^{-1}N^{-1}C}\]