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: 35

Answer

$379 $

Work Step by Step

To find how many turns of wire are needed, we first need to find the length of this wire. We know that the resistance is given by $$R=\dfrac{\rho L}{A} $$ Hence, the length of the wire is given by $$L_{\rm wire}= \dfrac{RA }{\rho_{\rm aluminum}}\tag 1$$ This length $L$ will make too many turns where the length of one turn is given by the circumference of one turn $$L_{\rm turn}=2\pi r_{\rm turn}\tag 2$$ Hence, the number of turns is given by $$N=\dfrac{L_{\rm wire}}{L_{\rm turn}}$$ Plug from (1) and (2); $$N=\dfrac{RA }{2\pi r_{\rm turn}\rho_{\rm aluminum}}$$ Plug the known; $$N=\dfrac{(1000)(10\times 10^{-6}\times 10\times 10^{-6})}{2\pi (1.5\times 10^{-3}) (2.8\times 10^{-8})}$$ $$N=\color{red}{\bf 379}\;\rm turn$$
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