A heat engine running backward is called a refrigerator if itspurpose is to extract heat from a cold reservoir. The same enginerunning backward is called a heat pump if its purpose is to exhaustwarm air into the hot reservoir. Heat pumps are widely used forhome heating. You can think of a heat pump as a refrigerator thatis cooling the already cold outdoors and, with its exhaust heat Q H, warming the indoors. Perhaps this seems a little silly, butconsider the following. Electricity can be directly used to heat ahome by passing an electric current through a heating coil. This isa direct, 100 % conversion of work to heat. That is, 16.0 \rm kW ofelectric power (generated by doing work at the rate 16.0 kJ/s atthe power plant) produces heat energy inside the home at a rate of16.0 kJ/s . Suppose that the neighbor's home has a heat pump with acoefficient of performance of 6.00, a realistic value. NOTE: With arefrigerator, \"what you get\" is heat removed. But with a heat pump,\"what you get\" is heat delivered. So the coefficient of performanceof a heat pump is K= Q H / W in . An average price for electricityis about 40 MJ per dollar. A furnace or heat pump will runtypically 300 hours per month during the winter. (Part A How muchelectric power (in kW ) does the heat pump use to deliver 16.0 kJ/sof heat energy to the house? /Part B What does one month's heatingcost in the home with a 16.0 kW electric heater? & Part C Whatdoes one month's heating cost in the home of a neighbor who uses aheat pump to provide the same amount of heating?
