A laboratory heat engine operates in a cyclic process while absorbing heat from a single high-temperature reservoir at TH. The engineer in charge claims that by suitable design the engine can be made to convert the entire heat input into mechanical work with no heat rejected.
Answer the following questions in the context of this claim.
(i) State the Kelvin–Planck statement of the second law of thermodynamics.
(ii) Give a qualitative explanation, based on the cyclic operation of a heat engine, why some amount of heat must necessarily be rejected to a cold reservoir.
(iii) Suppose an actual engine absorbs 1500J of heat from the source in each cycle and rejects 600J to the surroundings. Calculate the thermal efficiency of this engine and comment on whether it is consistent with the Kelvin–Planck statement.