Two wires, A and B, are made of the same material and have the same length. Wire A has half the diameter of wire B. If the resistance of wire A is R, the resistance of wire B is
A) 4R.
B) 2R.
C) R.
D) R/2.
E) R/4.

Question

Quizplus · Accepted Answer

The resistance of a wire is inversely proportional to the square of its diameter. Since wire A has half the diameter of wire B, wire B will have a resistance that is 1/(0.5^2) = 4 times less than that of wire A. Hence, the resistance of wire B is R/4.

Two Wires, a and B, Are Made of the Same