Thermal equilibrium

Thermal equilibrium is a thermodynamic concept in which all parts of a system are at the same temperature. This state results in no net flow of thermal energy between different parts of the system. The concept of thermal equilibrium is fundamental to the second law of thermodynamics, which states that if two physical systems are each in thermal equilibrium with a third one, then they are in thermal equilibrium with each other.

Overview

In a state of thermal equilibrium, all microstates that can be occupied by the system are equally likely. This is the principle of equiprobability. The state of thermal equilibrium is a state of maximum entropy, a concept that is explored in the field of statistical mechanics.

Zeroth law of thermodynamics

The zeroth law of thermodynamics establishes the concept of temperature and is fundamental to the definition of thermal equilibrium. It states that if two systems are each in thermal equilibrium with a third system, then they are in thermal equilibrium with each other. This law allows the establishment of a thermodynamic temperature scale.

Thermal equilibrium in statistical mechanics

In statistical mechanics, a system is in thermal equilibrium if the probability of the system being in a particular state is proportional to the number of microstates corresponding to that state. This is known as the Boltzmann distribution.

See also

• Heat
• Thermodynamic equilibrium
• Thermodynamic system
• Thermodynamic state

References

• File:Thermal equilibrium in closed system.png