The length of a certain wire is doubled while its radius is kept constant.What is the new resistance of this wire?
A)It stays the same.
B)It is 2 times as large.
C)It is 3 times as large.
D)It is 4 times as large.
E)It is ½ as large.

Question

Quizplus · Accepted Answer

The resistance $R$ of a wire is directly proportional to its length $L$ and inversely proportional to the square of its radius $r$, as given by the formula $R = \rho \frac{L}{A}$, where $A = \pi r^2$ is the cross-sectional area and $\rho$ is the resistivity of the material. Doubling the length of the wire doubles its resistance, since the radius (and thus the cross-sectional area) remains constant.

The Length of a Certain Wire Is Doubled While Its