What is thermal equilibrium?

Thermal equilibrium refers to a condition where two or more objects or systems are at the same temperature, resulting in no net flow of thermal energy between them. In this state, the heat transfer that occurs between the objects has reached a point where the amount of heat lost by one object is equal to the amount of heat gained by the other. This means that energy transfer ceases, leading to stable temperature conditions for the involved objects.

When two bodies are in thermal contact and they initially have different temperatures, heat will flow from the hotter body to the cooler one until the temperatures equalize. This process continues until they reach thermal equilibrium, at which point there is no further heat flow, and both bodies remain at the same temperature. Thus, the definition beautifully captures the essence of thermal behavior described in the laws of thermodynamics.

Other choices do not accurately reflect the concept of thermal equilibrium. For instance, the state of a single object absorbing maximum heat energy does not reference the condition of heat flow or temperature stabilization. Similarly, absolute zero pertains to a theoretical state where molecular motion nearly stops, but it does not inherently describe thermal equilibrium between two or more bodies. Finally, the mixture of gases at varying temperatures does not imply thermal equilibrium since those gases could