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Although Boltzmann first linked entropy and probability in 1877, the relation was never expressed with a specific constant until Max Planck first introduced k, and gave a more precise value for it (1.346 × 10 −23 J/K, about 2.5% lower than today's figure), in his derivation of the law of black-body radiation in 1900–1901. [11]
kT (also written as k B T) is the product of the Boltzmann constant, k (or k B), and the temperature, T.This product is used in physics as a scale factor for energy values in molecular-scale systems (sometimes it is used as a unit of energy), as the rates and frequencies of many processes and phenomena depend not on their energy alone, but on the ratio of that energy and kT, that is, on E ...
These include the Boltzmann constant, which gives the correspondence of the dimension temperature to the dimension of energy per degree of freedom, and the Avogadro constant, which gives the correspondence of the dimension of amount of substance with the dimension of count of entities (the latter formally regarded in the SI as being dimensionless).
The constant of proportionality, , is called the Stefan–Boltzmann constant. It has the value It has the value σ = 5.670 374 419 ... × 10 −8 W⋅m −2 ⋅K −4 .
The Boltzmann constant k B (alternatively k) may be used in place of the molar gas constant by working in pure particle count, N, rather than amount of substance, n, since: =, where N A is the Avogadro constant. For example, the ideal gas law in terms of the Boltzmann constant is:
Because the acoustic gas thermometry reached 0.2 ppm in uncertainty, and Johnson noise 2.8 ppm, this fulfilled the preconditions for a redefinition. After the 2019 redefinition, the kelvin was defined so that the Boltzmann constant is 1.380649×10 −23 J⋅K −1, and the triple point of water became experimentally measurable. [11] [12] [13]
This link is provided by Boltzmann's fundamental assumption written as S = k B ln Ω , {\displaystyle S=k_{\rm {B}}\ln \Omega ,} where k B is the Boltzmann constant , S is the classical thermodynamic entropy, and Ω is the number of microstates.
where is the Boltzmann constant (also written as simply ) and equal to 1.380649 × 10 −23 J/K, and is the natural logarithm function (or log base e, as in the image above). In short, the Boltzmann formula shows the relationship between entropy and the number of ways the atoms or molecules of a certain kind of thermodynamic system can be arranged.