Physics Technology Update (4th Edition)

Published by Pearson
ISBN 10: 0-32190-308-0
ISBN 13: 978-0-32190-308-2

Chapter 21 - Electric Current and Direct-Current Circuits - Problems and Conceptual Exercises - Page 761: 106

Answer

(a) $192\Omega$ (b) $96\Omega$ (c) $150W$

Work Step by Step

(a) We can find $R_1$ as follows: $R_1=\frac{V^2}{P_1}$ We plug in the known values to obtain: $R_1=\frac{(120)^2}{75W}$ $R_1=192\Omega$ (b) We can find $R_2$ as follows: As $R_1$ and $R_2$ are in series so $R_{eq}=R_1+R_2$ $\implies R_{eq}=\frac{V^2}{P_2}$ $\implies R_1+ R_2=\frac{V^2}{P_2}$ $\implies R_2=\frac{V^2}{P_2}-R_1$ We plug in the known values to obtain: $R_2=\frac{(120V)^2}{50W}-192\Omega$ $R_2=96\Omega$ (c) We can find the required power consumed as $P=\frac{V^2}{R_2}$ We plug in the known values to obtain: $P=\frac{(120V)^2}{96\Omega}$ $P=150W$
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