Thermodynamics/Definitions/Thermal

Temperature
The definition of temperature is very problematic. The problem is that we cannot define temperature from a macroscopic viewpoint.

A microscopic definition can be developed from statistical thermodynamics, but that is an advanced topic.

Units of Temperature
Temperature in thermodynamics is always given as absolute temperature.

Absolute temperature unit is Kelvin
 * Kelvin = &deg;C + 273

Note that the unit is a Kelvin not a "degree Kelvin" and no degree symbol is used.

Thermal Equilibrium
Even though we cannot define temperature, We can define the concept of thermal equilibrium


 * Thermal Equilibrium : When two systems (or subsystems) have the same temperature

Zeroth Law of Thermodynamics
If system A is in thermal equilibrium with system B, and system B is in thermal equilibrium with system C, then system A is in thermal equilibrium with system C.