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 33 - Electromagnetic Induction - Exercises and Problems - Page 999: 48

Answer

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Work Step by Step

$$\color{blue}{\bf [a]}$$ To find the induced current, we must find the induced emf first. The induced emf for a wire that moves in a magnetic field is given by $$\varepsilon=vlB$$ Plug the known, and refer to Figure 33.26. $$\varepsilon=(10)(0.2)(0.1)=\color{red}{\bf 0.2}\;\rm V$$ The induced current is given by $$I=\dfrac{\varepsilon}{R}$$ $$I=\dfrac{0.2}{1}=\color{red}{\bf 0.2}\;\rm A$$ $$\color{blue}{\bf [b]}$$ The wire is moving at a constant speed which means that the pulling force equals the magnetic force exerted on this wire. $$F_{\rm pull}=F_B$$ We know that the magnetic force exerted on a moving wire is given by $$F_{\rm pull} =BIL=(0.1)(0.2)(0.2)$$ $$F_{\rm pull} =\color{red}{\bf 4}\;\rm mN$$ $$\color{blue}{\bf [c]}$$ We know that the power dissipated in the carbon resistor is given by $$P=I^2R$$ where $P=Q/t$ where $Q$ is the amount of energy dissipated by the current and $t$ is the time interval. So $$I^2R=\dfrac{Q}{t}$$ Recalling that $Q=mc\Delta T$, $$I^2R=\dfrac{mc\Delta T}{t}$$ Hence, $$\Delta T=\dfrac{I^2Rt}{mc}$$ Plug the known; $$\Delta T=\dfrac{(0.2)^2(1.0)(10)}{(50\times 10^-6)(710)}$$ $$\Delta T=\color{red}{\bf 11.3}\;\rm K$$
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