Thermal equilibrium exists
It is characterized by a universal temperature
Within a system thermal equilibrium is formed
Two systems in thermal contact will exchange heat energy \(\Rightarrow\) a universal temperature in both systems result
This exchange process allows for temperature measurement with a thermometer
This exchange process is transitive; i.e. if a system is in thermal equilibrium with two other systems, both systems are in thermal equilibrium with each other (\(\Rightarrow\) This allows to compare systems of the same temperature)
Temperature measurements can e.g. be performed with a gas thermometer: For an ideal gas in thermal contact with another system one can e.g. measure the volume; applying the formula
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| \begin{equation*} p V = n R T \end{equation*} | (1.1) |
this defines the temperature of the gas.
But: the heat exchange can disturb the measured system
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© J. Carstensen (Stat. Meth.)