Q133 / 180 · KCET 2007 · Physics
A current of $5 \mathrm{~A}$ is passing through a metallic wire of cross-sectional area $4 \times 10^{-6} \mathrm{~m}^{2}$ If the density of charge carriers of the wire is
$5 \times 10^{26} \mathrm{~m}^{-3}$ the drift velocity of the electronswill be
- A$1 \times 10^{2} \mathrm{~ms}^{-1}$
- Correct answerB$1.56 \times 10^{-2} \mathrm{~ms}^{-1}$
- C$1.56 \times 10^{-3} \mathrm{~ms}^{-1}$
- D$1 \times 10^{-2} \mathrm{~ms}^{-1}$
Solution
Drift velocity, $v_{d}=\frac{1}{n e A}$
$$
\begin{aligned}
\Rightarrow v_{d} &=\frac{5}{\left(5 \times 10^{26}\right) \times\left(1.6 \times 10^{-19}\right) \times\left(4 \times 10^{-6}\right)} \\
&=\frac{1}{64}=1.56 \times 10^{-2} \mathrm{~ms}^{-1}
\end{aligned}
$$
Hence, the correct answer is option: 'B'.