Zeroth Law of Thermodynamics is essential to understand thermal equilibrium and measuring temperature. It is known as the “Zeroth Law” because it introduces the fundamental idea of temperature and constitutes the basis of thermodynamics, although having been developed after the first and second principles of thermodynamics.
Zeroth Law
The Zeroth Law of Thermodynamics states:
“If two systems, A and B, are each in thermal equilibrium with a third system, C then A and B are also in thermal equilibrium with each other.”
We can say more simple way, two bodies must be in thermal equilibrium with one another if they are independently in thermal equilibrium with a third body.
Explanation
Thermal Equilibrium: When there is no net heat transfer between items in contact and a system’s temperature stays constant over time, it is said to be in thermal equilibrium.
Third System (Reference Body): The third system (C), like a thermometer, serves as a reference and facilitates the comparison of two separate objects’ temperatures.
Temperature Concept: Temperature is a property that governs whether two systems will exchange heat, according to the Zeroth Law. They are in thermal equilibrium if their temperatures are equal since they won’t exchange heat.
Examples
Using a Thermometer: Heat moves from the water to the thermometer when it is submerged in hot water until thermal equilibrium is reached. We can conclude that two liquids have the same temperature if a different thermometer reads the same value in one of them.
Coffee and Spoon: A metal spoon slowly heats up when we stir a hot cup of coffee. The coffee and the spoon eventually achieve thermal equilibrium, which means that their temperatures equal to one another.
Air-Conditioned Room: After a prolonged period of air conditioning, all of the room’s items, including the walls and furniture, will finally achieve thermal equilibrium and equal the air’s temperature.
Importance of the Zeroth Law
Basis for Temperature Measurement: We can use thermometers to measure temperature by applying the Zeroth Law. A thermometer is a dependable instrument since it achieves equilibrium with the object it measures.
Understanding Heat Transfer: This law clarifies how heat transfers between objects and explains why heat always passes from a hotter body to a cooler one while maintaining equilibrium.
Useful Applications: The idea is applied in the design of thermal systems, including air conditioners, refrigerators, and even industrial operations where temperature regulation is vital.
Summary
The idea of thermal equilibrium is established by the Zeroth Law of Thermodynamics.
Two objects are in balance with one another if they are in balance with a third object.
The definition of temperature and the use of thermometers are based on this law.
This law is demonstrated in everyday situations such as using a thermometer, stirring hot coffee, or sitting in an air-conditioned environment.