a) A heat pump delivers 1000 calories to the inside of a house at 300 °K (27 °C)
ID: 1480178 • Letter: A
Question
a) A heat pump delivers 1000 calories to the inside of a house at 300 °K (27 °C). If the outside air temperature is 270 °K (-3 °C), how much mechanical work (in calories) must be supplied to the pump? b) Explain (quantitatively, not just words) why, given the efficiency of the heat pump (more calories of heat delivered than calories of work input to the heat pump), one can't take heat from the hot reservoir of the heat pump and make a perpetual motion machine by extracting enough energy to run the heat pump
Explanation / Answer
The Theoretical Efficiency of the heat pump is n = 1-(Tcold/Thot)
n= 1-270/300 = 0.1
The Efficiency of Heat Pump is 10 percent
The amount of work to be supplied to deliver 1000 calories is 10,000 calories.
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