Question

In case of four wires of same material, the resistance will be minimum when its length and diameters are respectively –

• A. L & D
• B. 2L & D
• C. L/2 &2D
• D. 2 L and D/2

Answer 1

Answer: (C)

L/2 &2D

Answer 2

R = $\frac{\delta\mathcal{l}}{A}$ = $\frac{4\delta\mathcal{l}}{\pi D^{2}}$ \ R µ $\frac{\mathcal{l}}{D^{2}}$

$\frac{\mathcal{l}}{D^{2}}$ is minimum for L/2 & 2D