University Physics with Modern Physics (14th Edition)

Published by Pearson
ISBN 10: 0321973615
ISBN 13: 978-0-32197-361-0

Chapter 20 - The Second Law of Thermodynamics - Problems - Exercises - Page 677: 20.16

Answer

See explanation.

Work Step by Step

(a) In one year, the freezer operates for 5 hours every day. The freezer operates for $ 5 h \times 365 \space days = 1825 h $ To find the operating power, $P = \frac{P_{kWh} }{t}$ $P = \frac{730 kWh }{1825 h }$ $P = 0.4 kW = 400 W$ (b) The maximum coefficient $K = \frac{268 K }{293 K- 268 K}$ $K = 10.72$ (c) $|W| = pt$ $|W| = (400 W) (3600s) $ $|W| = 1.44 \times 10^6 J$ $|Q_C| = K|W| $ $|Q_C| = 10.72(1.44 \times 10^6 J) $ $|Q_C| = 1.54 \times 10^7 J$ $Q = mC_W \Delta T + mL_f$ $Q = m(C_W \Delta T + L_f)$ $m = \frac{1.54 \times 10^7 J}{(4190 J/kg K) (20K) + (334 \times 10^3 J/kg)}$ $m = 36.86 kg $
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