Q. The drift velocity of the electrons in a copper wire of length 2 m under the application of a potential difference of 220 V is 0.5${ms}^{- 1}$. Their mobility ($in\ m^{2}V^{- 1}s^{- 1}$)
A) $2.5 \times 10^{- 3}$
B) $2.5 \times 10^{- 2}$
C) $5 \times 10^{2}$
D) $5 \times 10^{- 3}$
Explanation
(d) Drift velocity=mobility× intensity of electric field
or $v_{d} = \mu E\ \ \ \ or\ \mu = \frac{v_{d}}{E}$
$or\ \ \ \ \ \ \ \mu = \frac{v_{d}}{V/l}\ \ \ \ \ \ \ \ \ \ \ \ \ \left( \because E = \frac{V}{l} \right)$
$\therefore\mu = \frac{0.5 \times 2}{220} = 4.5 \times 10^{- 3}$
$\approx 5 \times 10^{- 3}m^{2}V^{- 1}s^{- 1}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.