Temperature Measurement

1. The definition of temperature as a physical quantity is based on the principle of thermal equilibrium.

2. Let say there are Thermometer A, Liquid B and Liquid C.

3. We put thermometer A into liquid B and then after thermal equilibrium is achieved we record the value.

4. We put thermometer A again into liquid C and after thermal equilibrium is achieved we record the value of reading in the thermometer.

5. If the temperature in both cases are the same, then liquid B and liquid C are in thermal equilibrium with one another. Eventhough, the two liquids (B and C) are not in thermal contact, they are in thermal equilibrium because their temperatures are the same.

6. Therefore Temperature is a physical quantity which determines whether or not two objects are in thermal equilibrium.