Question

Question: What does it mean to say that two systems are in thermal equilibrium?

Short answer

Answer

When you say that the two systems are in thermal equilibrium, it means that they are at the same temperature and that the rate of heat transfer in and out of the system is the same. In this situation, the systems are in contact with each other and they can exchange energy freely.

Step-by-step solution

Thermal equilibrium

When two systems or bodies are in contact with each other and there is no energy flow between them, we can say that the two systems are in thermal equilibrium with each other. Otherwise, we can say that the systems are in thermal equilibrium when they are at the same temperature.

Explanation

When two systems or bodies are in contact with each other and there is no energy flow between them, we can say that the two systems are in thermal equilibrium with each other. Otherwise, we can say that the systems are in thermal equilibrium when they are at the same temperature.

For example, when you take a hot cup of tea and is kept under room temperature, then after some time the heat gets transferred to the atmosphere because it is in contact with the surrounding air. And the process continues till the temperature of tea and atmosphere is equal.

Therefore, when two systems have the same temperature, they are said to be in thermal equilibrium.