Thermal Machines
Clausius' identification of S as a significant quantity was motivated by the study of reversible and irreversible thermodynamic transformations. A heat engine is a thermodynamic system that can undergo a sequence of transformations which ultimately return it to its original state. Such a sequence is called a cyclic process, or simply a cycle. During some transformations, the engine may exchange energy with its environment. The net result of a cycle is
- mechanical work done by the system (which can be positive or negative, the latter meaning that work is done on the engine),
- heat transferred from one part of the environment to another. In the steady state, by the conservation of energy, the net energy lost by the environment is equal to the work done by the engine.
If every transformation in the cycle is reversible, the cycle is reversible, and it can be run in reverse, so that the heat transfers occur in the opposite directions and the amount of work done switches sign.
Read more about this topic: Entropy (classical Thermodynamics)
Famous quotes containing the word machines:
“If men do not keep on speaking terms with children, they cease to be men, and become merely machines for eating and for earning money.”
—John Updike (b. 1932)