Zeroth Law of Thermodynamics

The Zeroth Law of Thermodynamics is a fundamental principle in thermodynamics that deals with thermal equilibrium. It states that if two systems are each in thermal equilibrium with a third system, then they must be in thermal equilibrium with each other.

Table of Contents:

• Zeroth Law of Thermodynamics
• Thermal Equilibrium
• Applications of Zeroth Law of Thermodynamics
• FAQs

What is Zeroth’s Law of Thermodynamics?

The Zeroth Law of Thermodynamics is a fundamental principle in thermodynamics that deals with thermal equilibrium. It states that if two systems are each in thermal equilibrium with a third system, then they must be in thermal equilibrium with each other.

In simpler terms, if two objects are each in thermal equilibrium with a third object, then they must be at the same temperature.

This law is called the “zeroth” law because it was added to the original set of thermodynamic laws after the first, second, and third laws were already established.

The Zeroth Law of Thermodynamics can be expressed mathematically as:

If system A is in thermal equilibrium with system C, and system B is in thermal equilibrium with system C, then system A and system B are in thermal equilibrium with each other.

Mathematically, this can be written as:

where TA, TB, and TC represent the temperatures of systems A, B, and C, respectively.

The Zeroth Law of Thermodynamics is important because it establishes the concept of temperature as a fundamental property of matter.

It also provides a basis for the construction of temperature scales and the measurement of temperature. Without the Zeroth Law, it would be impossible to define temperature in a consistent and meaningful way.

Thermal Equilibrium

Thermal equilibrium is a state in which two or more systems that are in contact with each other have the same temperature and do not exchange heat energy. When two systems are in thermal equilibrium, they are said to be in a state of balance and no further change occurs in the system.

In thermal equilibrium, the net transfer of heat energy between the systems is zero because they are at the same temperature. This means that the rates of heat transfer in both directions are equal, resulting in a constant temperature between the systems.

For example, when you put a hot object in contact with a cooler object, heat will flow from the hotter object to the cooler one until they reach the same temperature. When the two objects have reached the same temperature, they are said to be in thermal equilibrium, and no further transfer of heat occurs between them.

Thermal equilibrium is a fundamental concept in thermodynamics and is closely related to the Zeroth Law of Thermodynamics, which states that if two systems are each in thermal equilibrium with a third system, then they must be in thermal equilibrium with each other. This law provides a foundation for the construction of temperature scales and the measurement of temperature.

Applications of Zeroth Law of Thermodynamics

Here are some examples of the Zeroth Law of Thermodynamics in action:

• Using a thermometer to measure temperature: When you use a thermometer to measure the temperature of a substance, you are essentially testing whether the substance and the thermometer are in thermal equilibrium with each other. If they are, the thermometer will give an accurate reading of the substance’s temperature.

• Checking the temperature of food in a refrigerator: When you place a container of food in a refrigerator, it will eventually reach the same temperature as the air inside the refrigerator. This happens because the food and the air are in thermal contact and will exchange heat energy until they reach thermal equilibrium.

• Checking the temperature of water in a swimming pool: When you jump into a swimming pool, your body and the water will eventually reach thermal equilibrium. This means that your body and the water will be at the same temperature, and you will no longer feel cold when you are submerged.

• Checking the temperature of the air in a room: When you use a thermostat to control the temperature of a room, the thermostat will turn on the heating or cooling system until the room and the thermostat are in thermal equilibrium. This ensures that the temperature of the room remains constant.

• Checking the temperature of the human body: When a doctor uses a thermometer to measure your body temperature, they are testing whether your body and the thermometer are in thermal equilibrium. If they are, the thermometer will give an accurate reading of your body temperature.

Zeroth Law of Thermodynamics FAQS