Thermal equilibrium

Explain what is meant when two bodies are described as being in thermal equilibrium.

May/June 2016

State why two objects at the same temperature are said to be in thermal equilibrium.

May/June 2023

State what can be inferred from the temperature difference between two objects.

Oct/Nov 2017

Fig. 3.1 depicts a thermometer known as a constant volume gas thermometer. It is used to find the thermodynamic temperature $T$ of the gas in the glass bulb. The bulb is placed in the surroundings whose temperature is to be measured. The movable glass tube is then adjusted until the liquid level on the left-hand side is level with the reference line X on the fixed glass tube. Reference line Y is marked on the side of the movable glass tube. Because of the gas pressure in the glass bulb, the liquid at Y stands above the level at X. The height difference $\Delta h$ between the liquid levels at X and Y is then read from the scale. The thermodynamic temperature $T$ of the gas is directly proportional to the gas pressure. This pressure is directly proportional to $\Delta h$.

Oct/Nov 2025