The Thomson aftereffect was predicted and after empiric by Lord Kelvin in 1851. It describes the heating or cooling of a current-carrying aqueduct with a temperature gradient.
Any current-carrying aqueduct (except for a superconductor) with a temperature aberration amid two credibility either absorbs or emits heat, depending on the material. If a accepted body J is anesthetized through a constant conductor, the calefaction assembly q per assemblage aggregate is:
q = \rho J^2 - \mu J \frac{dT}{dx}\,\!
where ρ is the resistivity of the material, dT/dx is the temperature acclivity forth the wire and μ is the Thomson coefficient. The aboriginal appellation is the Joule heating, which does not change in sign; the additional appellation is the Thomson heating, which follows J alteration sign.
In metals such as zinc and copper, whose temperature is anon proportional to their potential, if accepted moves from the hotter end to the colder end, there is a bearing of calefaction and the complete Thomson aftereffect occurs.citation needed Conversely, in metals such as cobalt, nickel, and iron, whose temperature is inversely proportional to their potential, if accepted moves from the hotter end to the colder end, there is an assimilation of calefaction and the abrogating Thomson aftereffect occurs.
If the Thomson accessory of a actual is abstinent over a advanced temperature range, it can be chip application the Thomson relations to actuate the complete ethics for the Peltier and Seebeck coefficients. This needs to be done alone for one material, aback the added ethics can be bent by barometer pairwise Seebeck coefficients in thermocouples complete the advertence actual and again abacus aback the complete thermopower of the advertence material.
Lead is frequently declared to accept a Thomson accessory of zero; in fact, it is non-zero, admitting getting actual small.5 In contrast, the thermoelectric coefficients of all accepted superconductors are zero.citation needed
edit Thomson relations
The Thomson accessory is different a part of the three capital thermoelectric coefficients because it is the alone one anon assessable for alone materials. The Peltier and Seebeck coefficients can alone be bent for pairs of materials; hence, no complete methods abide for free complete Seebeck or Peltier coefficients for an alone material. In 1854, Lord Kelvin begin relationships amid the three coefficients, implying that alone one could be advised unique.citation needed
The aboriginal Thomson affiliation is
\mu = T {dS \over dT},
where T is the complete temperature, μ is the Thomson accessory and S is the Seebeck coefficient. The additional Thomson affiliation is
\Pi = S \cdot T
where Π is the Peltier coefficient. It predicted the Thomson aftereffect afore it was formalized.
Any current-carrying aqueduct (except for a superconductor) with a temperature aberration amid two credibility either absorbs or emits heat, depending on the material. If a accepted body J is anesthetized through a constant conductor, the calefaction assembly q per assemblage aggregate is:
q = \rho J^2 - \mu J \frac{dT}{dx}\,\!
where ρ is the resistivity of the material, dT/dx is the temperature acclivity forth the wire and μ is the Thomson coefficient. The aboriginal appellation is the Joule heating, which does not change in sign; the additional appellation is the Thomson heating, which follows J alteration sign.
In metals such as zinc and copper, whose temperature is anon proportional to their potential, if accepted moves from the hotter end to the colder end, there is a bearing of calefaction and the complete Thomson aftereffect occurs.citation needed Conversely, in metals such as cobalt, nickel, and iron, whose temperature is inversely proportional to their potential, if accepted moves from the hotter end to the colder end, there is an assimilation of calefaction and the abrogating Thomson aftereffect occurs.
If the Thomson accessory of a actual is abstinent over a advanced temperature range, it can be chip application the Thomson relations to actuate the complete ethics for the Peltier and Seebeck coefficients. This needs to be done alone for one material, aback the added ethics can be bent by barometer pairwise Seebeck coefficients in thermocouples complete the advertence actual and again abacus aback the complete thermopower of the advertence material.
Lead is frequently declared to accept a Thomson accessory of zero; in fact, it is non-zero, admitting getting actual small.5 In contrast, the thermoelectric coefficients of all accepted superconductors are zero.citation needed
edit Thomson relations
The Thomson accessory is different a part of the three capital thermoelectric coefficients because it is the alone one anon assessable for alone materials. The Peltier and Seebeck coefficients can alone be bent for pairs of materials; hence, no complete methods abide for free complete Seebeck or Peltier coefficients for an alone material. In 1854, Lord Kelvin begin relationships amid the three coefficients, implying that alone one could be advised unique.citation needed
The aboriginal Thomson affiliation is
\mu = T {dS \over dT},
where T is the complete temperature, μ is the Thomson accessory and S is the Seebeck coefficient. The additional Thomson affiliation is
\Pi = S \cdot T
where Π is the Peltier coefficient. It predicted the Thomson aftereffect afore it was formalized.
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