Non equilibrium conditions and temperature

[engineer23]

For non-equilibrium conditions, can temperature be defined?
Does this relate to the zeroeth law of thermo?

Thanks!

 

[Andy Resnick]

Sometimes a temeprature can be formally defined: the temperature of a 2-state atomic population during inversion, for example.

Generally, it is not possible to assign a unique temperature.

 

[astrokreng]

I can say that non-equilibrium conditions and temperature are closely related but temperature cannot be strictly defined in such conditions. Temperature is a measure of the average kinetic energy of particles in a system, and in non-equilibrium conditions, the distribution of kinetic energies is constantly changing. This makes it difficult to assign a single temperature value to the entire system.

This concept does relate to the zeroth law of thermodynamics, which states that when two systems are in thermal equilibrium with a third system, they are also in thermal equilibrium with each other. In non-equilibrium conditions, the systems are not in thermal equilibrium and therefore the zeroth law does not apply.

In non-equilibrium conditions, the laws of thermodynamics still apply but they may need to be modified or extended to accurately describe the behavior of the system. This is an area of active research and understanding non-equilibrium thermodynamics is crucial for many fields such as materials science, chemical reactions, and biological processes.