Q. A certain wire has a resistance $R.$ The resistance of another wire identical with the first except having twice its diameter is
A) $2\ R$
B) $0.25\ R$
C) $4\ R$
D) $0.5\ R$
Explanation
(b) $R \propto \frac{1}{A} \Rightarrow R \propto \frac{1}{r^{2}} \propto \frac{1}{d^{2}}$ [$d =$ diameter of wire]
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.