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 889: 60

Answer

${\bf 9.11}\;\rm A$

Work Step by Step

We know, according to Ohm's law, that $$\Delta V_{\rm tube}=IR$$ and since the battery is connected directly to the hollow nichrome tube, the hollow nichrome tube must have the same potential difference. Thus, $$\Delta V_{\rm battery}=IR$$ where $R=\rho L/A$ $$\Delta V_{\rm battery}=I\dfrac{\rho_{\rm nichrome }L}{A}$$ where $A$ is the cross-sectional area of the tube that faces the current which is given by $A=A_{out}-A_{in}=\pi (r^2_{\rm out}-r^2_{\rm in})$ $$\Delta V_{\rm battery}=I\dfrac{\rho_{\rm nichrome }L}{\pi (r^2_{\rm out}-r^2_{\rm in})}$$ Solving for $I$; $$I=\dfrac{\pi (r^2_{\rm out}-r^2_{\rm in}) \Delta V_{\rm battery}} {\rho_{\rm nichrome }L}$$ Plug the known; $$I=\dfrac{\pi ([1.5\times 10^{-3}]^2 -[1.4\times 10^{-3}]^2 ) (3)} {(1.5\times 10^{-6})(0.20)}$$ $$I=\color{red}{\bf 9.11}\;\rm A$$
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