He worked withLord Kelvin to develop an absolute thermodynamic temperature scale, which came to be called theKelvin scale. Joule also made observations ofmagnetostriction, and he found the relationship between thecurrent through aresistor and the heatdissipated, which is also calledJoule's first law. His experiments about energy transformations were first published in 1843.
James Joule was born in 1818, the son of Benjamin Joule, a wealthybrewer, and his wife, Alice Prescott, on New Bailey Street inSalford.[3] Joule was tutored as a young man by the famous scientistJohn Dalton and was strongly influenced by chemistWilliam Henry andManchester engineersPeter Ewart andEaton Hodgkinson. He was fascinated by electricity, and he and his brother experimented by giving electric shocks to each other and to the family's servants.[4]
As an adult, Joule managed the brewery. Science was merely a serious hobby. Sometime around 1840, he started to investigate the feasibility of replacing the brewery'ssteam engines with the newly inventedelectric motor. His firstscientific papers on the subject were contributed toWilliam Sturgeon'sAnnals of Electricity. Joule was a member of theLondon Electrical Society, established by Sturgeon and others.[citation needed]
Motivated in part by a businessman's desire to quantify the economics of the choice, and in part by his scientific inquisitiveness, he set out to determine which prime mover was more efficient. He discoveredJoule's first law in 1841, that "the heat which is evolved by the proper action of anyvoltaic current is proportional to the square of the intensity of that current, multiplied by the resistance toconduction which it experiences".[5] He went on to realize that burning apound of coal in a steam engine was more economical than a costly pound ofzinc consumed in an electricbattery. Joule captured the output of the alternative methods in terms of a common standard, the ability to raise a mass weighing one pound to a height of one foot, thefoot-pound.[citation needed]
However, Joule's interest diverted from the narrow financial question to that of how much work could be extracted from a given source, leading him to speculate about the convertibility of energy. In 1843 he published results of experiments showing that the heating effect he had quantified in 1841 was due to generation of heat in theconductor and not its transfer from another part of the equipment. This was a direct challenge to thecaloric theory which held that heat could neither be created nor destroyed. Caloric theory had dominated thinking in the science of heat since introduced byAntoine Lavoisier in 1783. Lavoisier's prestige and the practical success ofSadi Carnot's caloric theory of theheat engine since 1824 ensured that the young Joule, working outside eitheracademia or the engineering profession, had a difficult road ahead. Supporters of the caloric theory readily pointed to the symmetry of thePeltier–Seebeck effect to claim that heat and current were convertible in an, at least approximately,reversible process.[citation needed]
Joule was undaunted and started to seek a purely mechanical demonstration of the conversion of work into heat. By forcing water through a perforated cylinder, he could measure the slightviscous heating of the fluid. He obtained a mechanical equivalent of 770 foot-pounds force per British thermal unit (4,140 J/Cal). The fact that the values obtained both by electrical and purely mechanical means were in agreement to at least twosignificant digits was, to Joule, compelling evidence of the reality of the convertibility of work into heat.
Wherever mechanical force is expended, an exact equivalent of heat is always obtained.
— J.P. Joule, August, 1843
Joule now tried a third route. He measured the heat generated against the work done in compressing a gas. He obtained a mechanical equivalent of 798 foot-pounds force per British thermal unit (4,290 J/Cal). In many ways, this experiment offered the easiest target for Joule's critics but Joule disposed of the anticipated objections by clever experimentation. Joule read his paper to theRoyal Society on 20 June 1844,[8][9] but his paper was rejected for publication by the Royal Society and he had to be content with publishing in thePhilosophical Magazine in 1845.[10] In the paper he was forthright in his rejection of thecaloric reasoning of Carnot andÉmile Clapeyron, a rejection partlytheologically driven:[citation needed]
I conceive that this theory ... is opposed to the recognised principles of philosophy because it leads to the conclusion thatvis viva may be destroyed by an improper disposition of the apparatus: Thus Mr Clapeyron draws the inference that 'the temperature of the fire being 1000 °C to 2000 °C higher than that of the boiler there is an enormous loss ofvis viva in the passage of the heat from the furnace to the boiler.' Believing that the power to destroy belongs to the Creator alone I affirm ... that any theory which, when carried out, demands the annihilation of force, is necessarily erroneous.
Joule here adopts the language ofvis viva (energy), possibly because Hodgkinson had read a review of Ewart'sOn the measure of moving force to the Literary and Philosophical Society in April 1844.[citation needed]
In June 1845, Joule read his paperOn the Mechanical Equivalent of Heat to the British Association meeting inCambridge.[11] In this work, he reported his best-known experiment, involving the use of a falling weight, in which gravity does the mechanical work, to spin apaddle wheel in an insulated barrel of water which increased the temperature. He now estimated a mechanical equivalent of 819 foot-pounds force per British thermal unit (4,404 J/Cal). He wrote a letter to the Philosophical Magazine, published in September 1845 describing his experiment.[12]
Joule's Heat Apparatus, 1845
In 1850, Joule published a refined measurement of 772.692 foot-pounds force per British thermal unit (4,150 J/Cal), closer to twentieth century estimates.[13]
Joule's apparatus for measuring the mechanical equivalent of heat
Much of the initial resistance to Joule's work stemmed from its dependence upon extremelyprecise measurements. He claimed to be able to measure temperatures to within1⁄200 of a degree Fahrenheit (3 mK). Such precision was certainly uncommon in contemporary experimental physics but his doubters may have neglected his experience in the art of brewing and his access to its practical technologies.[14] He was also ably supported byscientific instrument-makerJohn Benjamin Dancer. Joule's experiments complemented the theoretical work ofRudolf Clausius, who is considered by some to be the coinventor of the energy concept.[citation needed]
Joule was proposing a kinetic theory of heat (he believed it to be a form of rotational, rather than translational,kinetic energy), and this required a conceptual leap: if heat was a form of molecular motion, why did the motion of the molecules not gradually die out? Joule's ideas required one to believe that the collisions of molecules were perfectly elastic. Importantly, the very existence ofatoms andmolecules was not widely accepted for another 50 years, though theessential work on the existence of molecules, atoms and electrons was underway throughout the 19th and early 20th centuries, from that ofJohn Dalton through toErnest Rutherford. A collection of Dalton’s works was published in 1893, 49 years after his death.[15]
Although it may be hard today to understand the allure of thecaloric theory, at the time it seemed to have some clear advantages.Carnot's successful theory of heat engines had also been based on the caloric assumption, and only later was it proved byLord Kelvin that Carnot's mathematics were equally valid without assuming a caloric fluid.[citation needed]
However, in Germany,Hermann Helmholtz became aware both of Joule's work and the similar 1842 work ofJulius Robert von Mayer. Though both men had been neglected since their respective publications, Helmholtz's definitive 1847 declaration of theconservation of energy credited them both.[16][17]
Also in 1847, another of Joule's presentations at the British Association inOxford was attended byGeorge Gabriel Stokes,Michael Faraday, and the precocious and maverickWilliam Thomson, later to become Lord Kelvin, who had just been appointed professor ofnatural philosophy at theUniversity of Glasgow. Stokes was "inclined to be a Joulite" and Faraday was "much struck with it" though he harboured doubts. Thomson was intrigued but sceptical.[citation needed]
Unanticipated, Thomson and Joule met later that year inChamonix. Joule married Amelia Grimes on 18 August and the couple went on honeymoon. Marital enthusiasm notwithstanding, Joule and Thomson arranged to attempt an experiment a few days later to measure the temperature difference between the top and bottom of theCascade de Sallanches waterfall, though this subsequently proved impractical.[citation needed]
Though Thomson felt that Joule's results demanded theoretical explanation, he retreated into a spirited defence of theCarnot–Clapeyron school. In his 1848 account ofabsolute temperature, Thomson wrote that "the conversion of heat (or caloric) into mechanical effect is probably impossible, certainly undiscovered"[18][19] – but a footnote signalled his first doubts about the caloric theory, referring to Joule's "very remarkable discoveries". Surprisingly, Thomson did not send Joule a copy of his paper but when Joule eventually read it he wrote to Thomson on 6 October, claiming that his studies had demonstrated conversion of heat into work but that he was planning further experiments. Thomson replied on the 27th, revealing that he was planning his own experiments and hoping for a reconciliation of their two views. Though Thomson conducted no new experiments, over the next two years he became increasingly dissatisfied with Carnot's theory and convinced of Joule's. In his 1851 paper, Thomson was willing to go no further than a compromise and declared "the whole theory of the motive power of heat is founded on two propositions, due respectively to Joule, and to Carnot and Clausius".[citation needed]
As soon as Joule read the paper he wrote to Thomson with his comments and questions. Thus began a fruitful, though largely epistolary, collaboration between the two men, Joule conducting experiments, Thomson analysing the results and suggesting further experiments. The collaboration lasted from 1852 to 1856, its discoveries including theJoule–Thomson effect, and the published results did much to bring about general acceptance of Joule's work and thekinetic theory.[citation needed]
Kinetics is the science of motion. Joule was a pupil of Dalton and it is no surprise that he had learned a firm belief in theatomic theory, even though there were many scientists of his time who were still skeptical. He had also been one of the few people receptive to the neglected work ofJohn Herapath on thekinetic theory of gases. He was further profoundly influenced byPeter Ewart's 1813 paper "On the measure of moving force".[citation needed]
Joule perceived the relationship between his discoveries and the kinetic theory of heat. His laboratory notebooks reveal that he believed heat to be a form of rotational, rather than translational motion.[citation needed]
Joule could not resist finding antecedents of his views inFrancis Bacon, SirIsaac Newton,John Locke,Benjamin Thompson (Count Rumford) and SirHumphry Davy. Though such views are justified, Joule went on to estimate a value for the mechanical equivalent of heat of 1,034 foot-pound from Rumford's publications. Some modern writers have criticised this approach on the grounds that Rumford's experiments in no way represented systematic quantitative measurements. In one of his personal notes, Joule contends that Mayer's measurement was no moreaccurate than Rumford's, perhaps in the hope that Mayer had not anticipated his own work.[citation needed]
Joule has been attributed with explaining the sunsetgreen flash phenomenon in a letter to theManchester Literary and Philosophical Society in 1869; actually, he noted the last glimpse as bluish green, without attempting to explain the phenomenon.[20]
"On the Mechanical Equivalent of Heat".Notices and Abstracts of Communications to the British Association for the Advancement of Science.15. 1845b. Read before the British Association at Cambridge, June 1845.
Joule died at home inSale[21] and is buried inBrooklands cemetery there. TheWetherspoons pub inSale, the town of his death, is named "The J. P. Joule" after him.
Joule received acivil list pension of£200per annum in 1878 for services to science
Albert Medal of theRoyal Society of Arts (1880), 'for having established, after most laborious research, the true relation between heat, electricity and mechanical work, thus affording to the engineer a sure guide in the application of science to industrial pursuits'
Joule married Amelia Grimes in 1847. She died in 1854, seven years after their wedding. They had three children together: a son, Benjamin Arthur Joule (1850–1922), a daughter, Alice Amelia (1852–1899), and a second son, Joe (born 1854, died three weeks later).
^OED: "Although some people of this name call themselves(dʒaʊl), and others(dʒəʊl) [the OED format for/dʒoʊl/], it is almost certain that J. P. Joule (and at least some of his relatives) used(dʒuːl)."
^Joule's unit of 1 ft lbf/Btu corresponds to5.3803×10−3 J/cal. Thus Joule's estimate was4.15 J/cal, compared to the value accepted by the beginning of the 20th century of4.1860 J/cal[6]
^Helmholtz, Hermann (1853)."Helmholtz on the Conservation of Force".Scientific Memoirs, Selected from the Transactions of Foreign Academies of Science, and from Foreign Journals, Natural Philosophy. Vol. I. p. 135. Retrieved13 December 2024.
Sibum, H. O. (1995). "Reworking the mechanical value of heat: instruments of precision and gestures of accuracy in early Victorian England".Studies in History and Philosophy of Science.26 (1):73–106.Bibcode:1995SHPSA..26...73S.doi:10.1016/0039-3681(94)00036-9.
Thomson, William (1848). "On an Absolute Thermometric Scale founded on Carnot's Theory of the Motive Power of Heat, and calculated from Regnault's Observations".Philosophical Journal.
Thomson, William (1882).Mathematical and Physical Papers. Cambridge: University Press.
Reynolds, Osbourne (1892).Memoir of James Prescott Joule. Vol. 6. Manchester, England: Manchester Literary and Philosophical Society. Retrieved5 March 2014.
Smith, C. (1998).The Science of Energy: A Cultural History of Energy Physics in Victorian Britain. London: Heinemann.ISBN0-485-11431-3.
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