| Definition: | SI unit of thermodynamic temperature, taking the fixed numerical value of the Boltzmann constant k to be 1,380 649 × 10−23 when expressed in the unit J/K, which is equal to kg m2 s−2 K−1, where the kilogram, metre and second are defined in terms of h, c and νCs
Note 1 to entry: The definition in the SI Brochure is: "The kelvin, symbol K, is the SI unit of thermodynamic temperature. It is defined by taking the fixed numerical value of the Boltzmann constant k to be 1,380 649 × 10−23 when expressed in the unit J K−1, which is equal to kg m2 s−2 K−1, where the kilogram, metre and second are defined in terms of h, c and ΔνCs."
Note 2 to entry: For 1 mol of an ideal gas, the internal energy is U = (3/2)kTNA, where k is the Boltzmann constant, T is the thermodynamic temperature, and NA is the Avogadro constant.
Note 3 to entry: The definition of the kelvin in IEV 112-02-08:2010-01 was: “SI unit of thermodynamic temperature, equal to the fraction 1/273,16 of the thermodynamic temperature of the triple point of water”.
Note 4 to entry: The kelvin is one of the seven SI base units: second (s), metre (m), kilogram (kg), ampere (A), kelvin (K), mole (mol) and candela (cd).
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