Boundaries and States
A reversible process changes the state of a system in such a way that the net change in the combined entropy of the system and its surroundings is zero. Reversible processes define the boundaries of how efficient heat engines can be in thermodynamics and engineering: a reversible process is one where no heat is lost from the system as "waste", and the machine is thus as efficient as it can possibly be (see Carnot cycle).
In some cases, it is important to distinguish between reversible and quasistatic processes. Reversible processes are always quasistatic, but the converse is not always true. For example, an infinitesimal compression of a gas in a cylinder where there exists friction between the piston and the cylinder is a quasistatic, but not reversible process. Although the system has been driven from its equilibrium state by only an infinitesimal amount, heat has been irreversibly lost due to friction, and cannot be recovered by simply moving the piston infinitesimally in the opposite direction.
Read more about this topic: Reversible Process (thermodynamics)
Famous quotes containing the words boundaries and/or states:
“Women’s art, though created in solitude, wells up out of community. There is, clearly, both enormous hunger for the work thus being diffused, and an explosion of creative energy, bursting through the coercive choicelessness of the system on whose boundaries we are working.”
—Adrienne Rich (b. 1929)
“Our citizenship in the United States is our national character. Our citizenship in any particular state is only our local distinction. By the latter we are known at home, by the former to the world. Our great title is AMERICANS—our inferior one varies with the place.”
—Thomas Paine (1737–1809)