Two solid conductors are made up of same material, have same length and same resistance. One of them has a circular cross section of area $A_1$ and the other one has a square cross section of area $A_2$. The ratio $A_1/A_2$ is

A 2

B 1.5

C 1

D 0.8

The answer is C.

Solution

$R=\rho\dfrac{l}{A}$. For the same material, length, and resistance, $A_1=A_2$ regardless of the shape of the cross-section, so $\dfrac{A_1}{A_2}=1$.

Concept Resistance, resistivity and cross-sectional area

130 questions from this chapter have appeared across 27 exam years.