Question

The resistivity of the material of potentiometer wire is $5\times {10}^{-5}\Omega m$ and its area of cross-section is $5\times {10}^{-6}{m}^2$. If $0.2A$ current is flowing through the wire, then the potential drop per metre length of the wire is

• A. $0.1V{m}^{-1}$
• B. $0.5V{m}^{-1}$
• C. $0.25V{m}^{-1}$
• D. $0.2V{m}^{-1}$
• E. $0.001V{m}^{-1}$

Answer 1

Answer: (D)

$0.2V{m}^{-1}$

Given, $i=0.2A$
Resistivity, $\rho =5\times {10}^{-6}\Omega -m$
and $A=5\times {10}^{-6}{m}^2,l=1m$
We know that, $V=iR$
$\Rightarrow V=\frac{i\rho L}{A}[\because R=\frac{\rho l}{A}]$
$\Rightarrow V=\frac{0.2\times 5\times {10}^{-6}\times 1}{5\times {10}^{-6}}$
$\Rightarrow V=0.2V{m}^{-1}$.