The Carnot cycle is a theoretical thermodynamic cycle that provides the maximum possible efficiency for a heat engine operating between two temperature reservoirs. It consists of two isothermal processes and two adiabatic processes.
Isothermal Process: A process in which the temperature remains constant while heat may be transferred into or out of the system.
Adiabatic Process: A process in which no heat is transferred to or from the system. All changes in internal energy are due to work done on or by the system.
Second Law of Thermodynamics: A fundamental principle stating that total entropy can never decrease over time for an isolated system; it also implies that perpetual motion machines are impossible.