Question

What is the formula for drift velocity in terms of relaxation time?

Answer 1

HC Verma sir has said equations derived for quantum probabilty are based on 'gross assumptions.'

He has used following to get drift velocity:

$path=ut+\frac{eE}{2m}t^2\\Where,u=0.\\path=\frac{eE}{2m}t^2\\Now,v_{_d}=\frac{path}{t}\\v_{_d}=\frac{eE}{2m}t$

Other writers have used:

$v=u+at\\v_{_d}=0+\frac{eE}{m}t\\v_{_d}=\frac{eE}{m}t$

You can use the negative sign to show opposite direction of and E