Question

The resistance of a hollow cylinder of copper of length 10 m and inner and outer radii 2cm and 3 cm respectively is (ρ copper = 2 ×10-8 Ω m)​

Answer 1

Answer: 1.27 × 10⁻⁴ Ω

Explanation:

The resistance R = ρ$\frac{l}{A}$

Given, l = 10 m

ρ =  2  × 10⁻⁸ Ω m

A = π (0.03 m )²  - π ( 0.02 m )²

= $\frac{22}{7}$ × $\frac{9}{10000}$ -

= $\frac{22}{7}$ × $\frac{(9-4)}{10000}$

= $\frac{11}{7000}$ m²

R = 2 × 10⁻⁸ × $\frac{70000}{11}$

= $\frac{14}{11}$ × 10⁻⁴

= 1.27 × 10⁻⁴ Ω