Question

a wire of length l and resistance r is stretched such that its length is doubled and the area of the cross-section is doubled, and the area of the cross-section is halved. how will its:- i.) resistance change ii.) resistivity change. justify your answers

Answer 1

Data: Let new length = l' new Area =, A' and  new resistance = R' Given, l' = 2l and A' = A/2 As we know R = (ρl) / A So, R' = [ρ × 2l] / (A/2) = (4 × ρl) / A = 4 × (ρ l / A )  but R = ρl/A ⇒  R' = 4 ×R Resitivity depends on the nature of material not on the length, temperature or Area of cross-section. So, resitivity will remain Constant.