A potential difference of 6 V is applied across a conductor of length 12 cm. If the mobility of electrons is \( 5.6 \times 10^{-6}\,\mathrm{m^2/V\,s} \), their drift velocity will be:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → \( 2.8 \times 10^{-4}\,\mathrm{m/s} \)
Mobility is the drift velocity per unit electric field, \( \mu = v_d/E \). The potential difference across the length of the conductor sets up a uniform field \( E = V/l \).
\( \displaystyle l = 12\,\mathrm{cm} = 0.12\,\mathrm{m} \)
\( \displaystyle E = \frac{V}{l} = \frac{6}{0.12} = 50\,\mathrm{V\,m^{-1}} \)
\( \displaystyle v_d = \mu E = 5.6\times10^{-6} \times 50 = 2.8\times10^{-4}\,\mathrm{m\,s^{-1}} \)