The drift velocity of electrons in a copper wire of length 2 m under the application of a potential difference of 200 V is $0.5 ms^{-1}$. The mobility of electrons in $m^2 V^{-1} s^{-1}$ is:

$5.0 \times 10^{-3}$

The correct answer is Option (2) → $5.0 \times 10^{-3}$

$v_d=μE$ [formula]

where,

$v_d$ = drift velocity = 0.5 m/s

$μ$ = mobility of electrons

E = electric field (v/m)

and,

$E=\frac{V}{L}$

where,

V = Potential difference = 200 V

L = length of wire = 2 m

$E=\frac{V}{L}=\frac{200}{2} = 100V/m$

and,

$v_d=μE$

$μ=\frac{0.5}{100}$

$=5.0 \times 10^{-3}m^2/Vs$