# Zeroth Law Of Thermodynamics

The Zeroth law of thermodynamics states that if two systems X and Y  separately attain thermal equilibrium with the third system Z. It means the two systems X and Y has a thermal equilibrium with each other.

Must Read: First Law of Thermodynamics

## Example of Zeroth Law Of Thermodynamics

For example: Consider two systems X and Y, which separated by an adiabatic wall. There is heat flow between system X and Z, and between Y and Z, due to which all three systems attain thermal equilibrium.

When the temperature becomes equal, heat flow stops.

TX = TZ and TY = TZ

## Important terms

This is an insulating wall which does not allow heat and matter to enter and leave.

If we take an example of two systems R and S separates from the Adiabatic wall. These two systems have different pressure and volume keeping temperature same.There will no flow of heat from one body to another because of insulation by the adiabatic wall.

Diathermic Wall

It is a Conducting wall that allows heat flows between any two systems.

Example: Two systems R and S separates from the diathermic wall. These two systems have different pressure and volume keeping temperature same.There will flow of heat from one body to another because of conducting diathermic wall.
Example: Any metal container(copper,aluminum),cup of tea.

## Thermal Equilibrium

In thermodynamics, if we say that the state of a system is in an equilibrium, it means macroscopic variables do not change in time.A gas enclosed in an insulated container having no effect of surroundings with the same pressure, volume, temperature, mass, and structure which do not change over time is in a state of thermodynamic equilibrium.

A system remains in equilibrium or not depends on the walls of container and system surroundings.

## More Examples

1. When a body of higher temperature contact with lower temperature, there will heat transfer from higher to the lower temperature objects.
2.  We feel cool after sweating in summers.

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