The coefficient of performance of refrigerator from second law of
Answer to Problem 1OQ
Option (d), finite.
Explanation of Solution
Second law of thermodynamics states that external work is necessary to pump heat from lower temperature to higher temperature. A refrigerator takes energy from cold reservoir and expels at hot reservoir. Refrigerator has to do work to convert heat from cold reservoir to hot reservoir. Coefficient of performance is the ratio of heat extracted from cold reservoir to work done on the refrigerant.
The maximum efficiency of a refrigerator is possible if it is working in Carnot cycle. The expression for efficiency is
Conclusion:
Therefore, according to second law of thermodynamics the coefficient of performance of a refrigerator must be finite. Thus, option (d) is correct.
Since coefficient of performance of refrigerator can be greater than 1, option (a) is incorrect.
Since coefficient of performance of refrigerator can be greater than 1, option (b) is incorrect.
Since coefficient of performance of refrigerator can be greater than or less than 1, option (c) is correct.
Since coefficient of performance of refrigerator can be zero, option (e) is incorrect.
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Chapter 22 Solutions
Physics for Scientists and Engineers with Modern, Revised Hybrid (with Enhanced WebAssign Printed Access Card for Physics, Multi-Term Courses)
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