XXXI.—On the Dynamical Theory of Heat. Part V. On the Quantities of Mechanical Energy contained in a Fluid in Different States, as to Temperature and Density
1853 ◽
Vol 20
(3)
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pp. 475-482
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Keyword(s):
The Body
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81. A body which is either emitting heat, or altering its dimensions against resisting forces, is doing work upon matter external to it. The mechanical effect of this work, in one case, is the excitation of thermal motions, and in the other, the overcoming of resistances. The body must itself be altering in its circumstances, so as to contain a less store of work within it, by an amount precisely equal to the aggregate value of the mechanical effects produced: and conversely, the aggregate value of the mechanical effects produced, must depend solely on the initial and final states of the body, and is therefore the same, whatever be the intermediate states through which the body passes, provided the initial and final states be the same.