Question

Two wires of the same material and same length have radii 1 mm and 2 mm respectively. Compare (i) their resistances, (ii) their specific resistance.

Answer 1

(i) Resistance is inversely proportional to cross-sectional area.

$\frac{R_1}{R_2}=\frac{A_2}{A_1}=\frac{\pi r_2^2}{\pi r_1^2}=\frac{2^2}{1^2}=4:1$

(ii) As they are made up of the same material, their specific resistances are the same.