Abstract
A BODY containing heat is in a condition from which it tends to release itself (by radiating or conducting away heat), and this tendency only ceases when the body has passed into a heatless condition. The temperature of a body is the measure of its tendency at any instant to recover this heatless state (cf. Maxwell, “Theory of Heat,” 10th ed. p. 32). This suggests a mechanical analogy; a body containing heat is analogous to an elastic medium in a state of strain, from which it tends to release itself in virtue of its restitutional forces; the magnitude of the restitutional force when a body is in a given strained condition measures its tendency to release itself from that strain, and so is analogous to the temperature of a body when in a given thermal condition. The quantity of work stored up in producing this strained condition, and which can be given out again when the body returns to its Un-strained condition, is analogous to the quantity of heat the body contains when at a given temperature; it is quite easy to show that we can completely represent the thermal condition of a body by means of a model consisting merely of an elastic rod subjected to a tension. A temperature, therefore, is analogous to a tension or pressure. We are now in a position to give a real physical meaning to the “temperature” of a body, and so enable it to be measured in absolute units like a mass or a length. Let us take a molecular body devoid of all heat motion and plunge it into a medium the temperature of which is T. Then the medium will exert an intermittent pressure or force on the molecules, thus setting them into motion and generating heat motion in the body. It can easily be shown that this force cannot be infinite, or a cold body placed in a hot medium would instantly acquire the temperature of the medium, whereas it always takes a definite time to do so.
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MARTIN, G. A Definition of Temperature. Nature 73, 390 (1906). https://doi.org/10.1038/073390b0
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DOI: https://doi.org/10.1038/073390b0
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