The Absolute Thermopower of Lead
The absolute thermopower of lead has been calculated from the results1 of direct measurement of its Thomson heat, μ, in the range from 10 to 350 K. The values for μ agree with those from the superconducting thermocouple experiment of Christian, Jan, Pearson and Templeton2 from 10 to 17 K, and with those from the indirect measurements of Borelius, Keesom, Johansson and Linde3 from about 80 to 300 K. From 17 to 80 K, however, the disagreement with the values used by Christian et al. 2 in constructing their absolute scale of thermoelectricity leads to a change in the scale of about 0.3 μV/K from 30 to 300 K. The abrupt nature of the change near 20 K makes a great difference to the shape of the calculated thermopowers of metals whose thermopowers are small (~ 1 μV/K). For example, the thermopowers of lead and the noble metals can be fitted to equations of the form S = aT + b/T from just above the phonon drag peak to about the Debye θ. This paper will be concerned with the Thomson heat experiment, the validity of the new scale for thermoelectricity, and plans for extending the scale to 1000°C.
KeywordsThermal Conductivity Absolute Scale Lead Wire Silver Gold Thermocouple Measurement
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