Physics for Scientists and Engineers: A Strategic Approach with Modern Physics (4th Edition)

Published by Pearson
ISBN 10: 0133942651
ISBN 13: 978-0-13394-265-1

Chapter 30 - Electromagnetic Induction - Exercises and Problems - Page 871: 37

Answer

$I(0) = 1.6$ A $I(1) = 0$ A $I(2) = -1.6$ A

Work Step by Step

Recall that Faraday's law is $\displaystyle \varepsilon_{induced} = \left|\frac{d\Phi_B}{dt}\right| = \left|\vec{A}\frac{d\vec{B}}{dt} + \vec{B}\frac{d\vec{A}}{dt}\right|$ In this problem, the cross-sectional area of the loop isn't changing so our equation becomes $\displaystyle \varepsilon_{induced} = \left|\vec{A}\frac{d\vec{B}}{dt}\right|$ Since we know the total resistance, we can say $I(t) = \displaystyle \frac{\varepsilon_{induced}}{R} = \frac{\vec{A}}{R}\cdot\frac{d\vec{B}}{dt} = \frac{\vec{A}}{R}\vec{B}$ $'(t)$ --- Given $\vec{B}(t) = 4t-2t^2 \qquad\rightarrow\qquad\vec{B}$ $'(t) = 4-4t$ $\qquad$ $\displaystyle \vec{A} = s^2 = (0.20)^2 = 4\times10^{-2}$ m$^2$ $I(t) \displaystyle = \frac{4\times10^{-2}}{0.10}(4-4t) = 0.4\cdot4(1-t)$ $I(t) = 1.6(1-t)$ $\therefore $ $I(0) = 1.6$ A $I(1) = 0$ A $I(2) = -1.6$ A
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