Reversible process (thermodynamics)

This prevents unbalanced forces and acceleration of moving system boundaries, which in turn avoids friction and other dissipation.

Additionally, the system must be in (quasistatic) equilibrium with the surroundings at all time, and there must be no dissipative effects, such as friction, for a process to be considered reversible.

[5] Reversible processes are useful in thermodynamics because they are so idealized that the equations for heat and expansion/compression work are simple.

An ideal thermodynamically reversible process is free of dissipative losses and therefore the magnitude of work performed by or on the system would be maximized.

The incomplete conversion of heat to work in a cyclic process, however, applies to both reversible and irreversible cycles.

The dependence of work on the path of the thermodynamic process is also unrelated to reversibility, since expansion work, which can be visualized on a pressure–volume diagram as the area beneath the equilibrium curve, is different for different reversible expansion processes (e.g. adiabatic, then isothermal; vs. isothermal, then adiabatic) connecting the same initial and final states.

Reversible processes define the boundaries of how efficient heat engines can be in thermodynamics and engineering: a reversible process is one where the machine has maximum efficiency (see Carnot cycle).

[7] Although the system has been driven from its equilibrium state by only an infinitesimal amount, energy has been irreversibly lost to waste heat, due to friction, and cannot be recovered by simply moving the piston in the opposite direction by the infinitesimally same amount.

The principle stated that some systems could be reversed and operated in a complementary manner.

During a demonstration of the Tesla turbine, the disks revolved and machinery fastened to the shaft was operated by the engine.