Describe the photo of the tea kettle at the beginning of this section in terms of heat transfer, work done, and internal energy. How is heat being transferred? What is the work done and what is doing it? How does the kettle maintain its internal energy?
The heat is transmitted to the tea kettle through the stove. The work done is the vaporization of water to the whistling of the tea kettle. The internal energy of the tea kettle is maintained by the process of heating the water inside it.
(a) What is the best coefficient of performance for a heat pump that has a hot reservoir temperature of 50.0ºC and a cold reservoir temperature of −20.0ºC ? (b) How much heat transfer occurs into the warm environment if 3.60×107 J of work ( 10.0kW ⋅ h ) is put into it? (c) If the cost of this work input is 10.0 cents/kW ⋅ h , how does its cost compare with the direct heat transfer achieved by burning natural gas at a cost of 85.0 cents per therm. (A therm is a common unit of energy for natural gas and equals 1.055×108 J .)
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