Drift velocity -  formula & derivation | Electric current | Physics | Khan Academy
Channel: Khan Academy India - English
Date: 2020-08-21

Let's derive the drift velocity formula (v = eEt/m), in terms of relaxation time. 
Drift velocity is the average velocity with which, the electrons drift in the opposite direction of the field. 
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. Here, t = relaxation time, the time between two successive collisions. 

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