n electrons, each carrying a charge -e, are flowing across a unit cross section of a metallic wire in unit time from east to west. Write an expression for electric current and also give its direction of flow. Give reason for your answer.
(b) The charge possessed by an electron is `1.6 times 10^-19` coulomb. Find the number of electrons that will flow per second to constitute a current of a 1 ampere.

Explanation

Electric current in a circuit defined as the time rate of flow of electric charge through any cross section and its direction is opposite to that of flow of electrons. Hence in present case electric current `I=q/t=(n e)/1=n e`
As electrons are flowing from east to west, the direction of electric current is from west to east.
(b) Here current I=1A, time t=1s and charge on each electron `e=1.6 times 10^18`
Hence, number of electrons flowing `n=(It)/e=(1 times 1)/(1.6 times 10^-19)=6.25 times 10^18`