Question

A wire of length 100 cm and area of cross-section 0.2 mm² has a resistance of 1.2 Ω. The specific resistance of the wire is:

Options

• 2.4 × 10⁻⁴ Ω cm

• 2.4 × 10⁻⁵ Ω cm

• 2.4 × 10⁻³ Ω cm

• 4.2 × 10⁻⁻⁴ Ω cm

Answer 1

2.4 × 10⁻⁵ Ω cm

Explanation:

In centimetres, a = 0.2 mm² = 0.002 cm²

 Using $$R=\rho\frac{l}{a}$$

$$\rho=\frac{Ra}{l}$$

$$=\frac{1.2\times0.002}{100}$$

= 2.4 × 10⁻⁵ Ω cm