Question

What is a quasi static process?

Answer 1

Hint: First we all know the meaning of quasi. We will see what it actually means. Then we will define a quasi static process and we will state its examples. Later we will discuss a common confusion if the quasi-static processes are reversible or not.

Complete answer:
A quasi-static process (also known as a quasi-equilibrium process) is a type of thermodynamic process. A thermodynamic process that occurs slowly enough for the system to maintain internal thermodynamic equilibrium (from the Latin quasi, meaning "as if").Quasi-static expansion is an example of this, in which the volume of a system changes so slowly that the pressure remains constant throughout the system at all times during the process.

A succession of equilibrium states characterizes such an idealised process, which is defined by infinite slowness. Only in a quasi-static process can we precisely define the system's intensive quantities (such as pressure, temperature, specific volume, and specific entropy) at each instant throughout the process; otherwise, because no internal equilibrium is established, different parts of the system would have different values of these quantities.

For a non-isothermal heat transfer mechanism, one favourite example is the addition of an endless number of intermediate-temperature reservoirs between the source and the sink. We examine the scenario and come to the conclusion that quasi-static processes are irreversible. Due to an unnecessary work term, no non-isothermal heat transfer process can ever be made reversible.

Note: Do not get confused between quasi-static and reversible processes . When friction is not present in a quasi-static process, it is the same as a reversible process. On the other hand if friction is missing then it will be only reversible.