The length of a metallic wire is increased by 20% and its area of cross section is reduced by 4%. The percentage change in resistance of the metallic wire is ______
Physics · Circular Motion
JEE Mains 6 April 2023 Shift 1 Morning Shift

Question

The length of a metallic wire is increased by 20% and its area of cross section is reduced by 4%. The percentage change in resistance of the metallic wire is ______

G1 Physics · Accepted Answer

Resistance is R = ρL/A Therefore, R₂/R₁ = (L₂/L₁)(A₁/A₂) Length increases by 20%: L₂ = 1.20L₁ Area decreases by 4%: A₂ = 0.96A₁ Hence, R₂/R₁ = 1.20/0.96 = 1.25 So resistance increases by 25%. Final value: 25