Drift Velocity

Class- XII - Physics

Drift Velocity:-

When a conductor is not subjected to any electric field, the electrons of the conductor are in random motion. Hence, the average velocity of electrons in a particular direction is zero.

But as soon as the conductor is subjected to an electric field , the electrons starts to move in the direction opposite to the direction of electric field . A time comes when the electrons start to move with a constant or steady velocity which is called dift velocity.

                Hence,  Drift velocity is the steady or the constant velocity attained by the electrons of a conductor when subjected to an electric field.

                Now, if 'l' be the length of the conductor, 'V' be the volume of the conductor, 'A' be the area of cross-section , 'e' be the charge of electron and 'n' be the number of electron per unit volume.

Then,

Volume of Conductor = A × l

Total no. of electrons = nAl

Total amount of charge = neAl

Where V_d is drift velocity, & J is the charge per unit area or charge density