Question

Calculate the resistivity of the material of a wire of 1m length , 0.4 mm diameter having a resistance 2 ohm

Answer 1

$let \: the \: resistivity \: be \: \alpha \\ \alpha = \frac{ra}{l} \\ = 2 \times \pi {(0.2 \times {10}^{ - 3} })^{2} \div 1 \\ = 8\pi \times {10}^{ - 8} ohm \: m \:$