Question

When are two bodies in thermal equilibrium?

a) When they have the same temperature.

b) When they have the same mass.

c) When they have the same volume.

d) When they have the same density.

Answer 1

Two bodies are in thermal equilibrium when they are in thermal contact and are at the same temperature. Thermal equilibrium occurs when two bodies are in contact with each other and can freely exchange energy.

Step-by-step explanation:

Two bodies are in thermal equilibrium when they are in thermal contact and are at the same temperature.

Thermal equilibrium occurs when two bodies are in contact with each other and can freely exchange energy. The zeroth law of thermodynamics states that when two systems, A and B, are in thermal equilibrium with each other, and B is in thermal equilibrium with a third system C, then A is also in thermal equilibrium with C.

For example, if you have two cups of water, one at 50 degrees Celsius and the other at 70 degrees Celsius, and you place them in thermal contact, heat will flow from the hotter cup to the cooler cup until they reach the same temperature. At this point, they are in thermal equilibrium.