Question

A copper coil is wound using copper wire of length $220m$ and diameter $2mm$. If the resistance of the coil is $1.19\Omega$, the resistivity of copper is:

• A. $1.7\times {10}^{-8}\Omega m$
• B. $1.7\times {10}^{-6}\Omega m$
• C. $2.25\times {10}^{-8}\Omega m$
• D. $1.95\times {10}^{-6}\Omega m$

Answer 1

The correct option is A $1.7\times {10}^{-8}\Omega m$

$\rho =\frac{RA}{1}=\frac{R(\pi d{)}^2}{4l}=\frac{1.19\times 22\times 4\times {10}^{-6}}{4\times 7\times 220}=\frac{1.19}{70}\times {10}^{-6}=1.7\times {10}^{-8}\Omega m$