Physics for Scientists and Engineers: A Strategic Approach with Modern Physics (3rd Edition)

Published by Pearson
ISBN 10: 0321740904
ISBN 13: 978-0-32174-090-8

Chapter 28 - The Electric Potential - Conceptual Questions - Page 832: 3


(a) Potential Energy, $U$ actually increases as $r$ increases. (b) Speed is less than at $f$ when the electron is at $i$.

Work Step by Step

The electric potential energy due to a charge placed a distance $r$ form the center of the positive point charge is $U=\frac{1}{4\pi \epsilon_{0}}$$\frac{q_{1}q_{2}}{r}$ The potential energy varies as $\frac{1}{r}$ but because the two charges have opposite signs, hence increasing $r$ simply means $U$ decreases but $U$ actually increases. (b) Since, two opposite charges slow down as they move farther apart, hence the speed decreases due to deceleration. Speed is less than at $f$ when the electron is at $i$.
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