Consider the entropy changes that occur during the Carnot cycle sketched in Figure 16.31. For each stage of the cycle, is the entropy change of the engine positive, negative, or zero? What is the total entropy change of the engine, and of the environment, during one complete cycle? Is there anything that would prevent a real engine from having the same entropy changes for each stage of its cycle?

Figure 16.31

2 3 TH W = Work done by engine Q = 0 Isothermal expansion Adiabatic expansion CARNOT CYCLE Tc Q = 0 Qc Qc Adiabatic compression Isothermal compression