Explain the mobility of a charge carrier in a conductor and derive its equation.

(N/A) Mobility $(\mu)$ is defined as the magnitude of the drift velocity $(v_d)$ per unit electric field $(E)$ applied across the conductor.
Mathematically, $\mu = \frac{|v_d|}{E}$.
Since the drift velocity is given by $v_d = \frac{eE\tau}{m}$, where $e$ is the charge, $\tau$ is the relaxation time, and $m$ is the mass of the carrier, substituting this into the mobility equation gives $\mu = \frac{e\tau}{m}$.
$SI$ unit: $\frac{m/s}{V/m} = m^2 V^{-1} s^{-1}$.
Dimensional formula: $[M^{-1} L^0 T^2 A^1]$.