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 30 - Current and Resistance - Exercises and Problems - Page 888: 45

Answer

a) $120\;\rm C$ b) $0.45\;\rm mm$

Work Step by Step

$$\color{blue}{\bf [a]}$$ We know that the current is given by $$I=\dfrac{Q}{t}$$ So the charge amount is given by $$Q=It$$ Plug the known; $$Q=(150)(0.8)$$ $$Q=\color{red}{\bf 120}\;\rm C$$ $$\color{blue}{\bf [b]}$$ To find the distance traveled by one electron on the wire during the 0.8-s, we need to find its drift speed. $$v_{\rm d}=\dfrac{J}{n_ee}=\dfrac{I}{An_ee}$$ where $v=s/t$, so $$v_{\rm d}=\dfrac{s}{t}=\dfrac{I}{An_ee}$$ Hence, the distance traveled by one electron is given by $$s= \dfrac{It}{An_ee}= \dfrac{It}{\pi r^2e (n_e)_{\rm copper}}$$ Plug the known; $$s= \dfrac{(150)(0.8)}{\pi (2.5\times 10^{-3})^2(1.6\times 10^{-19}) (8.5\times 10^{28})}$$ $$s=\color{red}{\bf 0.45}\;\rm mm$$
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