Question

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 $0.5$ $m s^{- 1}$ . 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. $4.5\times 10^{- 3}$

Answer 1

Answer: (D)

Drift velocity = mobility× intensity of the electric field
or $v_{d}=\mu E \, or \, \mu =\frac{v_{d}}{E}$
$or \, \mu =\frac{v_{d}}{V / l} \, \left(\because E = \frac{V}{l}\right)$
$\therefore \mu =\frac{0.5 \times 2}{220}=4.5\times 10^{- 3}m^{2}V^{- 1}s^{- 1}$