23. The Second Law of Thermodynamics

Refrigerators

Multiple Choice
A refrigerator has a coefficient of performance of 2.4. Each cycle, it takes in 3×10⁴ J of heat from the cold reservoir. How much is expelled to the hot reservoir?
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Multiple Choice
Freezing a kilogram of water, initially at 20°C, requires your refrigerator to remove about $417 kJ$ of thermal energy from the water. If the coefficient of performance of your refrigerator is 5.0, how much heat is exhausted into your kitchen when you freeze a kilogram of water?
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Multiple Choice
What is the maximum possible coefficient of performance for a refrigerator operating between 2.0°C (a typical refrigerator temperature) and 20°C (a typical kitchen temperature)?
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Textbook Question
A certain brand of freezer is advertised to use $730$ kWh of energy per year. 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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Textbook Question
A certain brand of freezer is advertised to use $730$ kWh of energy per year. Assuming the freezer operates for $5$ hours each day, how much power does it require while operating?
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Textbook Question
A refrigerator has a coefficient of performance of $2.25$ , runs on an input of $135$ W of electrical power, and keeps its inside compartment at $5$ °C. If you put a dozen $1.0$ -L plastic bottles of water at $31$ °C into this refrigerator, how long will it take for them to be cooled down to $5$ °C? (Ignore any heat that leaves the plastic.)
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