Question

An electric current of $8\text{A}$ exists in a metal wire of cross section ${10}^{-4}{\text{m}}^2$ and length $2\text{m}$. The drift speed of the free electrons in the wire will be (Given $n=5\times {10}^{28}{\text{m}}^{–3})$

• A. $2\times {10}^{-3}\text{m/s}$
• B. $1\times {10}^{-3}\text{m/s}$
• C. $2\times {10}^{-2}\text{m/s}$
• D. $1\times {10}^{-5}\text{m/s}$

Answer 1

The correct option is D $1\times {10}^{-5}\text{m/s}$

Drift velocity $\left(v_d\right)$ is given by
$v_d=\frac{i}{neA}$
$\Rightarrow v_d=\frac{8}{5\times {10}^{28}\times 1.6\times {10}^{-19}\times {10}^{-4}}$
$\Rightarrow v_d={10}^{-5}\text{m/s}$