The resistance of a wire of uniform diameter d and length l is R. The resistance of the another wire of the same material but diameter 2d and length 4l will be
Answer & explanation
Correct answer: option 2
$ R = \frac{\rho l}{A}$
$ \frac{R'}{R} = \frac{l'}{l} \frac{A}{A'} = 4\times \frac{1}{4} = 1$
$\Rightarrow R'= R$