Quasi Static Process (Nearly Static Process)

A quasi-static process is a process in which deviation from thermodynamic equilibrium is infinitesimal. And all the states through which passes during a quasi-static process is treated as equilibrium states. Thus, it can be defined as:
  “a succession of equilibrium states.”
For example, Consider a system, a gas contained in a cylinder fitted with a movable piston. If the piston is pushed in very rapidly, the gas immediately behind the piston acquires kinetic energy & is set into turbulent motion which is a non -equilibrium state.
In such a case the work done on the system is not quasi-static and is not governed by the equation dW= PdV. If however, the piston is pushed in infinitely slow rate, the system is in equilibrium state all the time & then the process can be considered quasi-static.

Some points on Quasi-Static Process:

1. A process of change in the state variable of the system, which is infinitesimally slow is called Quasi-Static process. Quasi-Static means nearly static.

2. In this process, the thermodynamical variables of the system change so slowly that the system continues to be in thermal & mechanical equilibrium.

3. The quasi-static process is only an idealized process. Thus, we can imagine that every state of a system is in thermal equilibrium.

4. It is a hypothetical construct. The process can be done in the infinite number of steps & it should not involve large temperature difference & accelerated the movement of the piston.
Thus, In this post we discussed the Quasi-Static process, any question, query, feedback, suggestions tell us in the comment section.
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