Question

The resistivity of a potentiometer wire is $40\times {10}^{-8}ohm-m$ and its area of cross section is $8\times {10}^{-6}{m}^2$. If a current of $0.2A$ is flowing through the wire, then the potential gradient will be

• A. ${10}^{-2}V/m$
• B. ${10}^{-1}V/m$
• C. $3.2\times {10}^{-2}V/m$
• D. $1V/m$

Answer 1

The correct option is A ${10}^{-2}V/m$

It is known that Potential gradient $=\frac{V}{L}=\frac{iR}{L}=$

$=\frac{i\rho L}{AL}=\frac{i\rho }{A}$

putting values according to question:

$P_{gradient}=\frac{0.2\times 40\times {10}^{-8}}{8\times {10}^{-6}}={10}^{-2}V/m$