Question Detail
Question
Resistance of wire is r Ω. Stretched to double length. New resistance?
Correct Answer
Option B is the correct answer.
Detailed Explanation
Volume constant: A₁L₁ = A₂L₂, L₂=2L₁ → A₂=A₁/2. R = ρL/A → R₂/R₁ = (L₂/L₁)×(A₁/A₂) = 2 × 2 = 4 → R₂=4r.
Hint
R ∝ L² when volume constant.