Final answer:
The efficiency of a reversible heat engine operating between two constant temperatures is maximum due to the second law of thermodynamics and the concept of the Carnot engine.
Step-by-step explanation:
According to the second law of thermodynamics, a Carnot engine operating between two given temperatures has the greatest possible efficiency of any heat engine operating between these two temperatures. Furthermore, all engines employing only reversible processes have this same maximum efficiency when operating between the same given temperatures.
This means that the efficiency of a reversible heat engine operating between two constant temperatures is maximum. This is because a reversible heat engine operates under ideal conditions with no energy losses, allowing it to extract the maximum amount of useful work from the heat energy it receives.
Therefore, to show that the efficiency of a reversible heat engine operating between two given constant temperatures is maximum, we can use the concept of the Carnot engine and the second law of thermodynamics.