Question Detail
Question
Two wires — A and B — with circular cross-sections have identical lengths and are made of the same material. Yet, wire A has four times the resistance of wire B. How many times greater is the diameter of wire B than wire A?
Correct Answer
Option C is the correct answer.
Detailed Explanation
Since R ∝ 1/d², R_A/R_B = (d_B/d_A)² = 4 implies d_B/d_A = 2, so wire B's diameter is twice that of wire A.
Hint
Resistance is inversely proportional to the square of the diameter — take the square root of the resistance ratio.