A heat engine operates cyclically between a large hot reservoir at 600 K and a cold reservoir at 300 K. In each cycle the engine absorbs 400 J of energy from the hot reservoir, does 100 J of mechanical work on the environment, and rejects 300 J of energy to the cold reservoir.
Assume the reservoirs are so massive that their temperatures remain effectively constant.
(a) Calculate the entropy change of the hot reservoir for one complete engine cycle. Include the sign and appropriate units.
(b) Calculate the entropy change of the cold reservoir for the same cycle.
(c) Determine the net entropy change of the universe (hot reservoir + cold reservoir + engine) for one cycle and state whether the second law is satisfied. Explain briefly.
(d) Redefine the system boundary to enclose the engine together with both reservoirs. What type of thermodynamic system is obtained? State the value and sign of the entropy change of this new system over one complete cycle, justifying your answer.