Meaning and Definition of Thermal equilibrium

Definition of thermal equilibrium

Thermal equilibrium is the State in which the temperatures of two bodies, which, in its initial conditions had different temperatures are equal. Once the temperatures match is suspended the flow of heat, reaching the mentioned term balance both bodies.
Thermal equilibrium is a concept that is part of thermodynamics, the branch of physics which deals describe the States of equilibrium at a macroscopic level.
When are two systems in direct mechanical contact, or failing that, separated by a surface that facilitates the transfer of heat, diathermic surface, it will be that both are in thermal contact. Meanwhile, at the end of a time, even if the two systems which are in thermal contact are arranged in such way that can not be mixed or even they are placed in the interior of a space in which it is impossible to exchange heat with the outside, inevitably, will reach the State of thermal equilibrium.
At a macroscopic level, the situation of two systems in thermal contact may be interpreted because the particles from the surface of the interface of the two systems are able to interact with each other; what you will see is that the particles of the system that boasts a higher temperature will transfer part of its energy to the particles of another system that observes a lower temperature. The aforementioned interaction will cause particles of both systems to achieve the same energy and the same temperature.
Thermometer device is used to be able to know the temperature that presents a body or substance. When the thermometer goes into thermal contact with the body in question both reach thermal equilibrium and then to the found at the same temperature, we know that temperature which indicates the thermometer in its index will be the temperature of the body that we are discussing.