The property which distinguishes thermodynamics from other science is temperature. One might say that temperature bears as important a relation to thermodynamics as force does to statics or velocity does to dynamics. Temperature is associated with the ability to distinguish hot from cold. When two bodies at different temperatures are brought into contact, after sometime they attain a common temperature and are then said to exist in thermal equilibrium.
"When a body A is in thermal equilibrium with a body B, and also separately with body C, then B and C will be in thermal equilibrium with each other".
This is known as the zeroth law of thermodynamics. It is the basis of temperature measurement.
In order to obtain a quantitative measure of temperature, a reference body is used, and a certain physical characteristic of this body which changes with temperature is selected. The changes in the selected characteristic may be taken as an indication of change in temperature. The selected characteristics is called the thermodynamic property, and the reference body which is used in the determination of temperature is called the thermometer. A very common thermometer consists of a small amount of mercury in an evacuated capillary tube. In this case the expansion of mercury in the tube is used as the thermometric property.
"When a body A is in thermal equilibrium with a body B, and also separately with body C, then B and C will be in thermal equilibrium with each other".
This is known as the zeroth law of thermodynamics. It is the basis of temperature measurement.
In order to obtain a quantitative measure of temperature, a reference body is used, and a certain physical characteristic of this body which changes with temperature is selected. The changes in the selected characteristic may be taken as an indication of change in temperature. The selected characteristics is called the thermodynamic property, and the reference body which is used in the determination of temperature is called the thermometer. A very common thermometer consists of a small amount of mercury in an evacuated capillary tube. In this case the expansion of mercury in the tube is used as the thermometric property.
