Drift Velocity—

The drift velocity is defined as the average velocity gained by the free electrons of a conductor in the opposite direction of the externally applied electric field.

Relaxation Time—

The average time that elapses between two successive collisions of an electron is called relaxation time.

Let we have a battery of voltage V is connected to the conductor of length ‘l’ and area of cross section ‘A’. let ‘n’ be the electron density in the conductor.

At room temp when battery is not connected across the conductor, electrons move with velocity of the order of 10⁵ m/sec. these velocity are distributed randomly in all direction.