Heat Engine In a heat engine the heat supplied to the engine is converted into useful work. If  Q2 is the heat supplied to the engine and Q1  is the heat rejected from the engine , then the net work done by the engine is given by W E =Q2 –Q1 The performance of a heat engine is expressed by it’s efficiency . We know that the efficiency or coefficient of performance of an engine Where –    WE = Work done by engine Ta = Atmospheric temperature   Refrigerator Refrigerator Read More