Thermal equilibrium occurs when two objects are at the same temperature and no heat flows between them. Which statement describes this condition?

• A. When two objects are at different temperatures and heat flows between them.
• B. When two objects are at the same temperature and no heat flows.
• C. When both objects are cooled to absolute zero.
• D. When energy is transferred only from the hotter to the cooler object.

Answer: (B)

When two objects are in thermal equilibrium, there is no net flow of heat between them. This happens because they have the same temperature, so the microscopic energy exchange balances out and heat transfer stops. The statement that describes this condition is the one where both objects are at the same temperature and no heat flows. If temperatures differ, heat will move from the hotter to the cooler object until they become equal, which means equilibrium hasn’t been reached yet. Absolute zero is not required for equilibrium to occur, and energy flowing only from hot to cold implies ongoing transfer, not equilibrium.