## College Physics (4th Edition)

Published by McGraw-Hill Education

# Chapter 18 - Multiple-Choice Questions - Page 697: 4

#### Answer

The correct answer is: (d) 1/2 as much

#### Work Step by Step

We can write an expression for the resistance of a wire: $R = \frac{\rho~L}{A} = \frac{\rho~L}{\pi~r^2}$ We can write an expression for the original resistance: $R_1 = \frac{\rho~L_1}{\pi~r_1^2}$ We can find an expression for the final resistance: $R_2 = \frac{\rho~L_2}{\pi~r_2^2}$ $R_2 = \frac{\rho~(2~L_1)}{\pi~(2~r_1)^2}$ $R_2 = \frac{2~\rho~L_1}{4~\pi~r_1^2}$ $R_2 = \frac{1}{2}~\frac{\rho~L_1}{\pi~r_1^2}$ $R_2 = \frac{1}{2}~R_1$ The correct answer is: (d) 1/2 as much

After you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.