# Thermal Equilibrium: Conditions and Application

• tme92
In summary, the question is whether a body with certain conditions can be in thermal equilibrium. The definition of thermal equilibrium is when the macroscopic state variables of a system are constant over time. However, in an isolated system, the flow of heat between all parts cannot be steady forever and will eventually equalize the temperature of the entire system. Therefore, while the body may have steady-state conditions, it is not in thermal equilibrium.
tme92
Can one say a body which has the conditions above mentioned be in thermal equilibrium? How does one apply the definition of temperature equilibrium to this situation?

(Physically I think it's possible for a body to be in this situation if some part of it receives heat from the outside and another loses heat)

Interesting question. I guess it's a matter of what you mean by thermal equilibrium. In many textbooks they say thermal equilibrium is when the macroscopic state variables (temperature, pressure, density,...) of the system are constant over time. In this sense you can say that your system is at equilibrium. But if you consider the whole isolated system your subsystem belongs to, this is not at equilibrium. The flow of heat between all the parts of the isolated system cannot be steady forever, but will forcefully vary over time, and finally vanish when all the parts of the complete system will be at the same temperature (this because an infinite heat reservoir doesn't exist).

tme92 said:
Can one say a body which has the conditions above mentioned be in thermal equilibrium? How does one apply the definition of temperature equilibrium to this situation?

(Physically I think it's possible for a body to be in this situation if some part of it receives heat from the outside and another loses heat)

The body is not in equilibrium, but may have steady-state conditions. Our bodies have these conditions: core temperature 98.6 F, skin temperature closer to ambient air temperature.

All this means is that there is a steady flow of heat, and T(x,t) = T(x).

## What is thermal equilibrium?

Thermal equilibrium is a state in which the temperature of a system remains constant and there is no net flow of heat from one part of the system to another. This means that the system's energy is evenly distributed and there is no heat transfer occurring.

## What are the conditions for thermal equilibrium to occur?

For thermal equilibrium to occur, the temperature of the system must be uniform and there must be no energy transfer occurring within the system. Additionally, the system must be isolated from its surroundings to prevent any external heat transfer.

## How is thermal equilibrium applied in everyday life?

Thermal equilibrium is applied in various ways in everyday life, such as in cooking, heating and cooling systems, and even in our own bodies. In cooking, thermal equilibrium is important for evenly cooking food. Heating and cooling systems use thermal equilibrium to maintain a desired temperature. Our bodies also maintain thermal equilibrium to regulate our internal temperature.

## What happens if thermal equilibrium is not achieved?

If thermal equilibrium is not achieved, there will be a net flow of heat from one part of the system to another, causing a temperature difference. This can result in uneven cooking, discomfort in temperature, and even damage to the system if it cannot handle the temperature difference.

## How does thermal equilibrium relate to the laws of thermodynamics?

Thermal equilibrium is closely related to the laws of thermodynamics, specifically the second law which states that energy will naturally flow from a region of higher energy to a region of lower energy until equilibrium is reached. This means that in order for thermal equilibrium to be achieved, the energy in a system must be evenly distributed.

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