Question

Find the electric field in the copper wire of area of cross section $2m{m}^2$ carrying a current of $1A.$ The resistivity of copper is $1.7\times {10}^{-8}\Omega m$.

• A. $4.25\times {10}^{-3}V/m$
• B. $8.5\times {10}^{-3}V/m$
• C. $8.5V/m$
• D. $9.5\times {10}^{-3}V/m$

Answer 1

Answer: (B)

$8.5\times {10}^{-3}V/m$

$R=\rho \frac{l}{A}\Rightarrow \rho =\frac{RA}{l}=\frac{RA}{V}\frac{V}{l}=\frac{A}{I}E=\frac{E}{J}\Rightarrow E=J\rho =\frac{1}{2\times {10}^{-6}}1.7\times {10}^{-8}=8.5\times {10}^{-3}V/m$