Question

An aluminium rod of length 3.14 m is of square cross-section $3.14\times 3.14m{m}^2$. What should be the radius of 1 m long another rod of same material to have equal resistance

• A. 2 mm
• B. 4 mm
• C. 1 mm
• D. 6 mm

Answer 1

The correct option is C 1 mm

By using $R=\rho .\frac{l}{A}\Rightarrow l\propto A\Rightarrow \frac{3.14}{1}=\frac{3.14\times 3.14\times {10}^{-6}}{\pi \times r^2}\Rightarrow r={10}^{-3}m=1mm$