If a copper wire is stretched to increase its length by 20%. The percentage increase in resistance of the wire i s __________ %.

Question

G1 Physics · Accepted Answer

Assuming resistivity remains unchanged and volume is constant, area A ∝ 1/L. Hence R = ρL/A ∝ L². If length increases by 20%, R'/R = (1.2)² = 1.44. Therefore resistance increases by 44%.