Thermal equilibrium is a condition in which two or more objects that are in thermal contact no longer exchange heat energy. This occurs when all the objects involved have reached the same temperature. At this point, the net flow of thermal energy between them becomes zero.

How It Works

When two objects at different temperatures come into contact, heat flows from the hotter object to the cooler one. This transfer continues until both objects reach the same temperature — this state is known as thermal equilibrium.

Key Characteristics

• No net heat transfer between objects in thermal contact
• Objects have the same temperature
• Occurs naturally as systems move toward a state of minimum energy imbalance

Example

If you place a hot metal spoon into a cup of cold water, the spoon will cool down and the water will warm up. Eventually, they will both reach the same temperature — at that point, they are in thermal equilibrium.

Importance in Physics

Thermal equilibrium is a foundational concept in thermodynamics. It is essential for defining temperature in a precise way and underlies the operation of thermometers and many heat-related calculations.

Written by Thenura Dilruk