Question

A wire of resistance R is stretched till its length is double of the original wire. Then, the resistance of the stretched wire is

• A. 2R
• B. 4R
• C. 8R
• D. 16R

Answer 1

Answer: (B)

4R

Answer 2

R ∝ l², (on stretching)

$\frac{R'}{R} = \left( \frac{\mathcal{l'}}{\mathcal{l}} \right)^{2} = \left( \frac{2\mathcal{l}}{\mathcal{l}} \right)^{2} = 4$

\ R¢ = 4R