Temperature Scales and Temperature Fixed Points

Abstract

Publisher Summary Temperature is one of the most important parameters in physics and the basic quantity of the SI system. This chapter provides knowledge of temperature in various points of a system that is needed in any cryogenic experiment. In low-temperature experiments, an accurate measurement of the temperature is usually more difficult than reaching that temperature. For example, if the thermal conductivity of a material is to be measured, at least two thermometers measuring a temperature difference are requested. The starting points of thermometry are the zeroth law and the second law of thermodynamics. The zeroth law justifies the existence of the thermometer, saying that two bodies A and B, which are in thermal equilibrium with a third body, are in thermal equilibrium with each other. There is no heat flow from one to the other, and they are said to be at the same temperature. The changes in temperature usually produce changes in physical properties such as dimension and electrical resistance. Such property variations can be used to measure the temperature changes. The approximate transition temperatures of some elements in zero magnetic field and critical fields are also reported.