Question

Consider a conductor of length 0.5 m. A potential difference of 20V is applied across this conductor. If the drift velocity of electrons is given as 5.0 × 10^-4ms^-1, then determine the mobility of the electrons.

(a) 5.25 × 10^18m^2V^-1s^-1

(b) 5.25 × 10^-18m^2V^-1s^-1

(c) 1.25 × 10^-5 m^2V^-1s^-1

(d) 1.25 × 10^6m^2V^-1s^-1

The question was asked during a job interview.

My enquiry is from Current Electricity in portion Current Electricity of Physics – Class 12

Answer 1

Right answer is (c) 1.25 × 10^-5 m^2V^-1s^-1

The explanation: Mobility = \(\frac {Drift \, velocity}{Electric \, field}\).

Electric field = \(\frac {Voltage}{length} = \frac {20}{0.5}\) = 40Vm^-1.

Mobility = \(\frac {Drift \, velocity}{Electric \, field} = \frac {5.0 \times 10^{-4}}{40}\) = 1.25 × 10^-5 m^2V^-1s^-1.