## What is the definition of Electron Drift Velocity?

Drift velocity is the average velocity with which electrons 'drift' in the presence of an electric field. It's the drift velocity (or drift speed) that contributes to the electric current. In contrast, thermal velocity causes random motion resulting in collisions with metal ions.

### Electron Drift Velocity Calculation

The calculation of electron drift velocity formula or equation is as below:

We start with the acceleration of the electrons,

a = F/m = eE/m.

The average velocity gained, i.e. the drift velocity, due to this acceleration = a*t = eEt/m.

The density of conduction electrons in copper. or 0.15 mm/s ! Compare this to the random thermal speed, of the electrons which are about 106 m/s or about 1010 times faster!.

So we learnt that when an external field is applied across the conductor the free electrons acquire a net velocity opposite to the direction of the electric field. These average velocity acquired by them is called drift velocity