Zeroth Law: If A is in thermal equilibrium with C, and B is in thermal equilibrium with C, what can be said about A and C?

Zeroth Law: If A is in thermal equilibrium with C, and B is in thermal equilibrium with C, what can be said about A and C?

• A. A and C are in thermal equilibrium with each other.
• B. A and C are not in thermal equilibrium.
• C. A has a higher temperature than C.
• D. B mediates the exchange only.

Answer: (A)

Thermal equilibrium means two systems in contact exchange no net heat and have the same temperature. If A is in thermal equilibrium with C, they share the same temperature and there is no net heat flow between them. That is exactly what it means for A and C to be in thermal equilibrium with each other. The Zeroth Law also tells us that if A is in equilibrium with C and B is in equilibrium with C, then A and B are in equilibrium with each other, reinforcing that equal temperature is a common property among all in contact. The other possibilities would require a temperature difference or an intermediary role that isn’t present here, so they don’t fit.

Thermal equilibrium means two systems in contact exchange no net heat and have the same temperature. If A is in thermal equilibrium with C, they share the same temperature and there is no net heat flow between them. That is exactly what it means for A and C to be in thermal equilibrium with each other. The Zeroth Law also tells us that if A is in equilibrium with C and B is in equilibrium with C, then A and B are in equilibrium with each other, reinforcing that equal temperature is a common property among all in contact. The other possibilities would require a temperature difference or an intermediary role that isn’t present here, so they don’t fit.