Physics: Principles with Applications (7th Edition)

Published by Pearson
ISBN 10: 0-32162-592-7
ISBN 13: 978-0-32162-592-2

Chapter 15 - The Laws of Thermodynamics - Misconceptual Questions: 10

Answer

Choice A.

Work Step by Step

Page 423 states “real engines that are well designed reach 60 to 80 percent of the Carnot efficiency.” Assuming 400 K (the average temperature of the hot parts) for the hot reservoir and 300 K for the cold reservoir, the maximum efficiency is about 25 percent, and 0.6 to 0.8 of this is closest to 20 percent efficient. The other choices are not reasonable. For example, a hot reservoir temperature of about 1800 kelvin would be needed to select choice B, and that is too hot.
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