Derive equa1ion of mobility in terms of relaxation time `(tau)`. Wrile its unit.

Explanation

`rArr` Drift velocity of electron in presence of external electric field,
`|v_(d) | = (Ee)/(m) .tau` (Velocity = acceleration `xx ` time )
`tau ` = time interval between two successive collision
`(|v_(d)|)/(E) = (e tau)/(m)`
`therefore mu = (e tau )/(m)`
SI unit `(ms^(-1))/(Vm^(-1)) = m^(2) V^(-1) S^(-1)`