The length of a wire is halved, and its radius is doubled. The resistance will change by a factor of
A) 4
B) 2
C) 1/2.
D) 1/4.
E) 1/8.

Question

Quizplus · Accepted Answer

Resistance is inversely proportional to the cross-sectional area and directly proportional to the length. Halving the length reduces resistance by a factor of 1/2, and doubling the radius increases the area by a factor of 4, reducing resistance by another factor of 1/4. Combined, the resistance changes by a factor of 1/8.

The Length of a Wire Is Halved, and Its Radius