Question

Hello every one does anyone know about Operational definitions in Thermodynamics?

Answer 1

Hey @satish27may and welcome to OpenStudy!
Although it is a term I don't use a lot, I have a vague understanding of the term I can try pass on to you:

In thermodynamics an operational definition is a definition of a physical quantity (could be the macroscopic properties such as temperature and pressure), which provides the required operations to measure it in a laboratory.

A perfect example which I like to use for this is temperature:
When we usually define temperature we say:
"temperature is the average translational kinetic energy of the species within the system"
While this definition explains the relationship between the average translational kinetic energy and temperature, we are NO WHERE closer in the search for a way to MEASURE it.

For this purpose we got the zeroth law of thermodynamics, which exactly gives an operational definition of temperature by releasing it to the thermal equilibrium!
(I will be quoting my own notes now and link is provided in the bottom of this answer)

"If a closed system has a diathermic boundary a thermal equilibrium between the system and the surroundings can occur, which applies there is no change in the system or the surroundings if they are in contact. In short there is no exchange of energy in the form of heat if the system and the surroundings have the \(\color{red}{same~temperature}\)"

In short the zeroth law of thermodynamics provide us with the following information:
1) Temperature is a property which tells us something about thermal equilibrium.
2) This means if two systems have the same temperature, there will be thermal equilibrium, if they are connected by a diathermic boundary.

By this definition we motivate the introduction and helps the understanding of the concept “temperature”.

Very similar concept can be used for pressure.

Sources:
My own notes: http://openstudy.com/users/frostbite#/updates/55daf37ce4b05a670c277d75
Kestin, Joseph. A Course in Thermodynamics. Vol. 1. 1979.

Answer 2

by relating it to the thermal equilibrium!*

Answer 3

Thank you Frostbite for your valuable
responce