University Physics (14th Edition)
14th Edition
ISBN: 9780133969290
Author: Hugh D. Young, Roger A. Freedman
Publisher: PEARSON
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Textbook Question
Chapter 20, Problem 20.16E
A certain brand of freezer is advertised to use 730 kW·h of energy per year. (a) Assuming the freezer operates for 5 hours each day, how much power does it require while operating? (b) If the freezer keeps its interior at −5.0°C in a 20.0°C room, what is its theoretical maximum performance coefficient? (c) What is the theoretical maximum amount of ice this freezer could make in an hour, starting with water at 20.0°C?
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A power plant has been proposed that would make use of the temperature gradient in the ocean. The system is to operate between 20.0°C (surface water temperature) and 5.00°C (water temperature at a depth of about 1 km). (a) What is the maximum efficiency of such a system? (b) If the useful power output of the plant is 75.0 MW, how much energy is absorbed per hour? (c) In view of your answer to part (a), do you think such a system is worthwhile (considering that there is no charge for fuel)?
(a) What is the best coefficient of performance for a refrigerator that cools an environment at −30.0ºC and has heat transfer to another environment at 45.0ºC ? (b) How much work in joules must be done for a heat transfer of 4186kJ from the cold environment? (c) What is the cost of doing this if the work costs 10.0 cents per 3.60×106 J (a kilowatthour)?(d) How many kJ of heat transfer occurs into the warm environment?(e) Discuss what type of refrigerator might operate between these temperatures.
100 mL of water at 20.0 °C is placed in the freezer compartment of a refrigerator with a coefficient of performance of 3.00. How much heat energy is exhausted into the room as the water is changed to ice at
-15.0 °C?
Express your answer with the appropriate units.
Chapter 20 Solutions
University Physics (14th Edition)
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