Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
A thermodynamic system is in thermal equilibrium if its macroscopic variables (such as pressure , volume , and temperature ) do not change with time when the system is isolated.
An adiabatic wall is an insulating wall (e.g., wood or asbestos) that does not allow the flow of heat energy between systems, meaning .
A diathermic wall is a conducting wall (e.g., copper or aluminum) that allows the flow of heat energy between systems until they reach thermal equilibrium.
The Zeroth Law of Thermodynamics states that if two systems, and , are separately in thermal equilibrium with a third system , then and are also in thermal equilibrium with each other.
The physical significance of the Zeroth Law is that it provides a basis for the concept of Temperature. It implies that there exists a scalar quantity called temperature, which is the same for all systems in thermal equilibrium.
Temperature is the property that determines whether a system is in thermal equilibrium with other systems. If , the systems are in thermal equilibrium.
📐Formulae
💡Examples
Problem 1:
Two systems and are separated by an adiabatic wall, but each is in contact with a third system through a diathermic wall. After a long time, the adiabatic wall between and is replaced by a diathermic wall. Will there be any change in the states of and ?
Solution:
No, there will be no change in the states of and . According to the Zeroth Law of Thermodynamics, since is in equilibrium with () and is in equilibrium with (), then and are already in thermal equilibrium with each other (). Replacing the adiabatic wall with a diathermic wall will not trigger any heat flow.
Explanation:
The Zeroth Law ensures that systems at the same temperature do not exchange net heat, even if a conducting path is introduced between them.
Problem 2:
A mercury thermometer is placed in a beaker of water. After some time, the mercury level stops rising. Explain this in terms of the Zeroth Law.
Solution:
When the mercury level becomes stationary, the thermometer (system ) is in thermal equilibrium with the water (system ). If we then use the same thermometer to measure another liquid (system ) and find the same mercury level, we can conclude and , therefore .
Explanation:
The thermometer acts as the 'third system' mentioned in the Zeroth Law, allowing us to compare the temperatures of two different bodies without bringing them into direct contact.