What is the reason behind choosing adiabatic and isothermal process for carnot engine?
My book states the following reason. I am not able to understand it. It would be great if you could put it in simpler words.
A process is not quasi-static if it involves finite temperature difference between the system and reservoir. Hence, in a reversible heat engine operating between two temperatures, heat should be absorbed and released isothermally.
Employing any other processes other than adiabatic, say isochoric, to take the system from one temperature to another, we shall need series of reservoirs in the temperature range $T_2$ and $T_1$ to ensure that the process is quasi-static.