Question

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

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

Answer 1

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

Potential gradient $=\frac{V}{L}=\frac{iR}{L}=\frac{i\rho L}{AL}=\frac{i\rho }{A}=\frac{0.2\times 40\times {10}^{-8}}{8\times {10}^{-6}}={10}^{-2}V/m$