A copper wire has a length of 3.2 m and a cross‑sectional area of 0.7 mm². The resistivity of copper at 20°C is $1.68\times 10^{-8}\Omega \text{m}$. Calculate the resistance of the wire.

Step-by-step solution

1. Convert the area from mm² to m²: $0.7{\text{ mm}}^2=0.7\times 10^{-6}{\text{ m}}^2$.
2. Use $R=\rho L/A$: $R=(1.68\times 10^{-8}\times 3.2)/(0.7\times 10^{-6})$.
3. Compute numerator: $1.68\times 10^{-8}\times 3.2=5.376\times 10^{-8}$.
4. Divide by denominator: $5.376\times 10^{-8}/0.7\times 10^{-6}=0.0768\Omega$.
5. Round to three significant figures: $0.077\Omega$.

Concept tested: Resistance calculation using resistivity

Published 16 October 2026 · How this solution was prepared and checked