# Relationship between temperature and thermal equilibrium

### Temperature and Thermal Equilibrium - Physics LibreTexts

Relationship between heat and temperature At thermal equilibrium, the temperature of the thermometer bulb and the water bath will be the same, and there. The pressure difference (for mechanical equilibrium) and temperature difference (for thermal equilibrium) should be zero between system and surroundings for. NASA Logo - Web Link to fim-mdu.info + Text Only Site Two objects separately in thermodynamic equilibrium with a third object are in equilibrium with each other Thermodynamic equilibrium leads to the large scale definition of temperature.

When this stage is achieved the substances are said to be in thermal equilibrium.

Thus, we can generalize that 'heat energy always flows from a hotter body to a colder body till their temperatures are equalized'. Or to put it differently - 'A cold body does not become hot on its own, to raise its temperature, external heat energy must be supplied to it'.

We can also say, 'the temperature of a substance determines the direction of heat flow between the substances, when they are introduced together'.

## An Explanation of Thermal Equilibrium and its Formulas With Examples

So, equilibrium occurs when observable or macroscopic changes in a system cease to change with the passage of time.

Thermal equilibrium of a system does not mean complete uniformity or stability within a system. For example, a river system can be in thermal equilibrium when the macroscopic or externally measurable temperature is stable and not changing in time, even though the surrounding or spatial temperature distribution reflects degradation of water quality leading to changes in temperature. Another example is when the thermometer is placed in contact with the patient's body, If the body temperature of the patient and that of the mercury in the clinical thermometer have reached thermal equilibrium, then the temperature of the thermometer is the same as the body temperature, hence the reading of the thermometer shows the body temperature of the patient.

Further illustration of this point is observed when food is put in the refrigerator, the heat from the food is transferred into the air of the refrigerator.

The refrigeration process continues till thermal equilibrium is achieved and temperature of the food is equal to the temperature of the air in the refrigerator. Calculation of Thermal Equilibrium When a cold and hot object are placed together they will eventually come to an equilibrium. This resulting final temperature will be somewhere in between the two initial temperatures.

This is apparent as the colder object will heat up while the hotter object will cool down. A classic example of this is thermal equilibrium of water filled with ice, wherein the 'system' is the warm room, glass, ice and water. The temperature of the ice will increase thereby decreasing the temperature of water. So, evidently the amount of heat lost by the hotter object will be given to the colder object.

## Heat and temperature

Or use the Law of Conservation of Energy: Find out at what temperature will they come to thermal equilibrium? As you may have already learned, many physical quantities are defined solely in terms of how they are observed or measured, that is, they are defined operationally. Temperature is operationally defined as the quantity of what we measure with a thermometer. As we will see in detail in a later chapter on the kinetic theory of gases, temperature is proportional to the average kinetic energy of translation, a fact that provides a more physical definition.

Differences in temperature maintain the transfer of heat, or heat transfer, throughout the universe.

### Heat and temperature (article) | Khan Academy

Heat transfer is the movement of energy from one place or material to another as a result of a difference in temperature. You will learn more about heat transfer later in this chapter. Thermal Equilibrium An important concept related to temperature is thermal equilibrium.

Two objects are in thermal equilibrium if they are in close contact that allows either to gain energy from the other, but nevertheless, no net energy is transferred between them. Even when not in contact, they are in thermal equilibrium if, when they are placed in contact, no net energy is transferred between them.

If two objects remain in contact for a long time, they typically come to equilibrium. In other words, two objects in thermal equilibrium do not exchange energy.

Experimentally, if object A is in equilibrium with object B, and object B is in equilibrium with object C, then as you may have already guessed object A is in equilibrium with object C. That statement of transitivity is called the zeroth law of thermodynamics. The first, second, and third laws of thermodynamics were already named and numbered then. The zeroth law had seldom been stated, but it needs to be discussed before the others, so Fowler gave it a smaller number.

• Thermal equilibrium
• 1.1: Temperature and Thermal Equilibrium
• What is the relationship between temperature and thermal equilibrium?

Consider the case where A is a thermometer.