Question

The resistance of 100 m long copper wire with diameter 1 mm is ___ ohms. (${\text{Copper}}_{\rho }=1.6\times {10}^{-8})$ ohm-m

• A. 2.04
• B. 20.4
• C. 0.204
• D. 204

Answer 1

The correct option is A 2.04

Given: Length of copper wire = 100 m
Radius of copper wire = 0.5 mm = 0.5 x 0.001 m
(${\text{Copper}}_{\rho }=1.6\times {10}^{-8})$ ohm-m

Using the relationship,
R = ρ$\frac{L}{A}$
We have,
R = $\frac{1.6\times {10}^{-8}\times 100}{3.141\times (0.5\times 0.001{)}^2}$
= 2.04 ohms