Hostname: page-component-745bb68f8f-5r2nc Total loading time: 0 Render date: 2025-02-08T22:04:53.663Z Has data issue: false hasContentIssue false
  • English
  • Français

1. An Account of Carnot's Theory of the Motive Power of Heat,* with Numerical Results deduced from Regnault's Experiments on Steam†

Published online by Cambridge University Press:  16 March 2015

William Thomson
William Thomson
Affiliation:
of Glasgow.
Get access

Extract

The questions to be resolved by a complete theory of the motive power of heat, are the following:—

I. What is the precise nature of the thermal agency by means of which mechanical effect is to be produced, without effects of any other kind?

II. How may the amount of this thermal agency necessary for performing a given quantity of work be estimated?

Type
Proceedings 1848-49
Information
Proceedings of the Royal Society of Edinburgh , Volume 2 , 1851 , pp. 198 - 204
Copyright
Copyright © Royal Society of Edinburgh 1850

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

page 198 note ‡ The passage quoted in the text is translated from a note to p. 37, in Carnot's Treatise.

page 199 note * I cannot omit this opportunity of correcting an expression which I made use of in a note published in the Philosophical Magazine (vol. xxxiii., p. 315), in alluding to the generation of heat by such operations, which I inadvertently asserted to have been proved by “known experiments, adduced by Mr Joule.” It is true that the evolution of heat in a fixed conductor, through which a galvanic current is sent from any source whatever, has long been known to the scientific world; but it was pointed out by Mr Joule that we cannot infer, from any previously published experimental researches, the actual generation of heat when the current originates in electro-magnetic induction, since the question occurs, Is the heat which is evolved in one part of the closed conductor merely transferred from those parts which are subject to the inducing influence? Mr Joule, after a most careful experimental investigation, with reference to this question, finds that it must be answered in the negative. (See a paper “On the Calorific Effects of Magneto-Electricity, and on the Mechanical Value of Heat; by J. P. Joule, Esq.;” read before the British Association at Cork, in 1843, and subsequently communicated by the author to the Philosophical Magazine, vol. xxiii., pp. 263, 347, 435.)

Before we can finally conclude that heat is absolutely generated in such operations, it would be necessary to prove that the inducing magnet does not become lower in temperature, and thus give compensation for the heat evolved in the conductor. I am not aware that any examination, with reference to the truth of this conjecture, has been instituted; but in the case when the inducing body is a pure electro-magnet (without any iron) the experiments actually performed by Mr Joule render the conclusion probable, that the heat evolved in the wire of the electro-magnet is not affected by the inductive action otherwise than through the reflected influence, which diminishes the strength of its own current.

page 202 note * This is well established by experiment, within the ordinary atmospheric limits, in Regnault's Etudes Météorologiques, in the Annales de Chimie.