Two objects have reached the same temperature and no energy is exchanged. What describes their relation?

• A. Thermal Conductivity
• B. Thermal Equilibrium
• C. Thermal Transience
• D. Thermal Gradient

Answer: (B)

Thermal equilibrium is reached when two bodies in contact have the same temperature, so there is no net heat flow between them. That exactly describes the situation here: both objects share the same temperature and no energy moves from one to the other.

Other terms describe different ideas: thermal conductivity is about how easily a material conducts heat, not the relation between two objects; thermal transience (transience) refers to the temporary state as a system moves toward equilibrium; and a thermal gradient is a spatial temperature difference that drives heat flow. Since there is no temperature difference and no energy exchange, the situation is thermal equilibrium.