In the context of the Carnot cycle, what are isothermal processes characterized by?

In the context of the Carnot cycle, isothermal processes are characterized by a constant temperature. This means that during these stages of the cycle, the system exchanges heat with its surroundings without changing its temperature. In specific terms, when the working substance (often an ideal gas) is in an isothermal state, it absorbs or releases heat while the internal energy remains unchanged due to the temperature stability.

This is crucial in the Carnot cycle, as two of its four processes are isothermal: one where heat is absorbed from a hot reservoir and one where heat is expelled to a cold reservoir. The efficiency of the Carnot cycle is maximized during these isothermal processes because they represent reversible exchanges of heat that help to generate work. The concept of constant temperature is essential in understanding heat engines and the second law of thermodynamics, which indicates that heat flows spontaneously from a hotter object to a colder one but not the reverse without external work.