A wire of 1 Ω has a length of 1 m . It is stretched till its length increases by 25 % . The percentage change in resistance to the nearest integer is :

Step-by-step solution

R 0 = 1   Ω    R 1 = ℓ 0 = 1   m    ℓ 1 = 1 . 25   m A 0 = A As volume of wire remains constant so A 0 ℓ 0 = A 1 ℓ 1 ⇒ A 1 = ℓ 0   A 0 ℓ 1 Now, Resistance R = ρ ℓ A R 0 R 1 = ℓ 0 / A 0 ρ ℓ 1 / A 1 1 R 1 = ℓ 0   A 0 ℓ 0   A 0 ℓ 1 × ℓ 1 R 1 = ℓ 1 2 ℓ 0 2 = 1 . 5625   Ω So % change in resistance = R 1 - R 0 R 0 × 100 % = 1 . 5625 - 1 1 &#21