In existographies, James Joule (1818-1889) (IQ:180|#167) (Murray 4000:16|P) [Kanowitz 50:17] [Cropper 30:3|T] (GPE:28) [CR:120] was an English engineer and physicist noted for his experiments in the determination of the mechanical equivalent of heat, one of the precursors to the logic behind both the first and second law of thermodynamics. Joule was the son of a wealthy brewer who was tolerant enough of the scientific interests of his son to furnish him with a home laboratory, in which his elaborate experiments on the inter-conversion of forms of energy, from heat, gravitational, to mechanical, to electric, etc., were conducted. [1] See main: Mechanical equivalent of heatInto the late 1830s, while working by day as a brewer, Joule, at night, was said to have been searching for the appropriate principles of the construction of an electromagnetic engine that would rival the steam engine with respect to commercial efficiency. By 1841, however, he realized that the inherent limitations of the electric motor would not allow it to outperform the steam engine; this setback, it is said, is what prompted him to consider the interrelationships between heat and electricity. [7]
“I shall lose no time in repeating and extending these experiments, being satisfied that the grand agents of nature are … indestructible; and that wherever mechanical force is expended, an exact equivalent of heat is always obtained.”
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| Left: Joule doing one of his mechanical equivalent of heat experiments: measuring the conversion of electrical energy into heat, as measured by a thermometer. Right: engraving of Joule’s 1843 apparatus for measuring the mechanical equivalent of heat, from an 1869 issue Harper’s New Monthly Magazine. [3] |
See main: Joule's second lawIn 1844, Joule, in his “On the Changes of Temperature produced by the Rarefaction and Condensation of Air”, stated the following summary, in respect to his two previous mechanical equivalent of heat experiments:
“The mechanical equivalents of heat derived from the foregoing experiments were so near 838 lbs, the result of magnetical experiments in which ‘latent heat’ could not be suspected to interfere in any way, as to convince me that the heat evolved was simply the manifestation, in another form, of the mechanical power expended in the act of condensation.”— James Joule (1844), “On the Changes of Temperature produced by the Rarefaction and Condensation of Air” (pg. 180) [10]
“Heat is a substance, invariable in quantity, not convertible into any other element, and incapable of being generated by any physical agency.”
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| Joules' famous 1847 Niagara Falls honeymoon experiment, where he measured the mechanical equivalent of heat; an indirect motive of which was to find experimental proof for the genesis theory of creation, as described in the Bible. |
See main: Niagara Falls; See also: Thermodynamics anecdotesJoule’s draw to experimentation, much of it done at the family brewery, was such that Joule rarely left home without scientific apparatus. Indeed, while visiting a waterfall with his wife on their honeymoon in 1847, he produced a thermometer with which to measure the change in the temperature of the water as it fell. [5]
“The mechanical equivalents of heat determined by the various series of experiments given in this paper are 823, 795, 820, 814, and 760. The mean of the last three, which I take as least liable to error, is 798 lb., a result so near 838 lbs, the equivalent which I deduced from my magnetical experiments, as to confirm, in a remarkable manner, the above explanation of the phenomena described in this paper, and to afford a new and, to my mind, powerful argument in favor of the ‘dynamical theory of heat’ which originated with Bacon, Newton, and Boyle, and has been at a later period so well supported by the experiments of Rumford, Davy, and Forbes.”— James Joule (1844), “On the Changes of Temperature produced by the Rarefaction and Condensation of Air” (pg. 187) [10]
“The principles I have adopted lead to a theory of the steam-engine very different from the one generally received, but at the same time much more accordant with facts. It is the opinion of many philosophers that the mechanical power of the steam-engine arises simply from the passage of heat from a hot to a cold body, no heat being necessarily lost during the transfer. This view has been adopted by Clapeyron in a very able theoretical paper, of which there is a translation in the Third part of Taylor's Scientific Memoirs. This philosopher agrees with Carnot in referring the power to vis viva developed by the caloric contained by the vapor in its passage from the temperature of the boiler to that of the condenser. I conceive that this theory, however ingenious, is opposed to the recognized principles of philosophy, because it leads to the conclusion that vis viva may be destroyed by an improper disposition of the apparatus.”— James Joule (1844), “On the Changes of Temperature produced by the Rarefaction and Condensation of Air” (pg. 188)
“The height of the pulleys from the ground was twelve yards, and consequently, when the weights had descended through that distance, they had to be wound up again in order to renew the motion of the paddle. After this operation had been repeated sixteen times, the increase of the temperature of the water was ascertained by means of a very sensible and accurate thermometer.”— James Joule (1845), “On the Existence of an Equivalent Relation between Heat and the Ordinary Forms of Mechanical Power” (Ѻ)(Ѻ)
“It was from Dalton’s instruction, that I first formed a desire to increase my knowledge of original research.”— James Joule (c.1870), Publication
