State the formula of an electric current and define its unit.

Explanation

If a net amount of electric charge 9 flows across any cross-section of a conductor in time t, then the current I, through the crosssection is
`I = Q/t` ....(12.1)
SI unit of electric charge is coulomb (C) and time is second (s).
The SI unit of electric current is ampere (A), named after the French scientist, Andre-Marie Ampere.
Hence from equation (12.1), A= `C/s`
Definition of ampere (A): If I coulomb charge flows through any cross-section of a conductor in 1 second, then the electric current flowing through the conductor is said to be l ampere.
`i.e., 1 A = (1C)/(1s) = 1Cs^(-1)`