Question

The drift velocity of electron in a copper wire of length $2m$ under the application of a potential difference of $200 V$ is $0.5 \,ms ^{-1} $ Their mobility is (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. $5 \times 10^{-3}$

Answer 1

Answer: (D)

Mobility $\mu=\frac{v_{d}}{E}$
$V=200 \,V $ $\,\,\,\,\,\,\,$ $ v _{ d }=0.5 \,ms ^{-1}$ $\,\,\,\,\,\,\,$ $\ell=2 \,m$
As we know: $E =\frac{ V }{\ell}$
$\Rightarrow \mu=\frac{ v _{ d }}{ V } \times l $
$\mu=\frac{0.5}{200} \times 2=5 \times 10^{-3} m ^{2} V ^{-1} s ^{-1}$