Question

Two conductors are made of the same material and have the same length. Conductor A is solid wire of diameter 1mm. Conductor B is hollow tube of outer diameter 2mm and inner diameter 1mm. The ratio of resistance $R_A$ to $R_B$.

• A. 3:1
• B. 1:3
• C. 1:1
• D. 2:1

Answer 1

Answer: (A)

3:1

As we know,

$R=\rho \times \frac{l}{A}$

Then

$\frac{R_A}{R_B}=\frac{A_B}{A_A}=\frac{2^2-1^2}{1^2}=3$