Question

A certain wire has a resistance$R$. The resistance of another wire identical with the first except having twice its diameter is

• A. $2R$
• B. $0.25R$
• C. $4R$
• D. $0.5R$

Answer 1

Answer: (B)

$0.25R$

Answer 2

$R \propto \frac{1}{A} \Rightarrow R \propto \frac{1}{r^{2}} \propto \frac{1}{d^{2}}$ [d = diameter of wire]