Heat pump - a heat pump is a heat engine run in reverse. In winter it pumps heat from the cold air outside into the wanner air inside the building, maintaining the building at a comfortable temperature. In summer, it pumps heat from the cooler air inside the building into the warmer air outside, acting as an air conditioner.

a) If the outside temperature in winter is -5.0°C, and the inside temperature is 17°C, how many Joules of heat will the heat pump deliver to the inside for each joule of electrical energy used to run the unit, assuming an ideal Camot cycle?

b) Suppose you have the option of using electrical resistance heating rather than a heat pump. How much electrical energy would you need in order to deliver the same amount of heat to the inside of the house as in part (a)?

[Note that the dependency of the efficiency of a heat pump on the temperature difference of the hot and cold reservoirs is opposite to that of a Camot engine. The heat pump is less efficient when the temperature difference increases].