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The second law of thermodynamics may be expressed in many specific ways, [23] the most prominent classical statements [24] being the statement by Rudolf Clausius (1854), the statement by Lord Kelvin (1851), and the statement in axiomatic thermodynamics by Constantin Carathéodory (1909). These statements cast the law in general physical terms ...
[1] [2] [3] A more fundamental statement was later labelled as the zeroth law after the first three laws had been established. The zeroth law of thermodynamics defines thermal equilibrium and forms a basis for the definition of temperature: if two systems are each in thermal equilibrium with a third system, then they are in thermal equilibrium ...
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The Planck statement applies only to perfect crystalline substances: As temperature falls to zero, the entropy of any pure crystalline substance tends to a universal constant. That is, lim T → 0 S = S 0 {\displaystyle \lim _{T\to 0}S=S_{0}} , where S 0 {\displaystyle S_{0}} is a universal constant that applies for all possible crystals, of ...
Deriving the Stefan–Boltzmann Law using Planck's law. The law can be derived by considering a small flat black body surface radiating out into a half-sphere. This derivation uses spherical coordinates , with θ as the zenith angle and φ as the azimuthal angle; and the small flat blackbody surface lies on the xy-plane, where θ = π / 2 .
The Clausius statement states that it is impossible to construct a device whose sole effect is the transfer of heat from a cool reservoir to a hot reservoir. [3] Equivalently, heat spontaneously flows from a hot body to a cooler one, not the other way around.
kelvin: K thermodynamic temperature "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 m 2 s −2 K −1, where the kilogram, metre and second are defined in terms ...
The Planck relation [1] [2] [3] (referred to as Planck's energy–frequency relation, [4] the Planck–Einstein relation, [5] Planck equation, [6] and Planck formula, [7] though the latter might also refer to Planck's law [8] [9]) is a fundamental equation in quantum mechanics which states that the energy E of a photon, known as photon energy, is proportional to its frequency ν: =.