Question

A current of $5\text{A}$ is passing through a metallic wire of cross sectional area $14\times {10}^{-6}{\text{m}}^2$. If the density of the charge carries in the wire is $5\times {10}^{26}{\text{C/m}}^3$, the drift speed of the electrons.

• A. $3.46\times {10}^{-3}{\text{ms}}^{-1}$
• B. $4.46\times {10}^{-3}{\text{ms}}^{-1}$
• C. $5.46\times {10}^{-3}{\text{ms}}^{-1}$
• D. $6.46\times {10}^{-3}{\text{ms}}^{-1}$

Answer 1

The correct option is B $4.46\times {10}^{-3}{\text{ms}}^{-1}$

$I=5\text{A};A=14\times {10}^{-6}{\text{m}}^2;n=5\times {10}^{26}{\text{C/m}}^3$

Charge of an electron,$e=1.6\times {10}^{-19}\text{C}$

Drift speed $V_d=\frac{I}{neA}$

Substituting the data given in the question,

$V_d=\frac{5}{5\times {10}^{26}\times 1.6\times {10}^{-19}\times 14\times {10}^{-6}}$

$V_d=\frac{1}{16\times 14}=\frac{1}{244}=4.46\times {10}^{-3}{\text{ms}}^{-1}$