Joule, James Prescott
Joule, James Prescott
(b. Salford, near Manchester, England, 24 December 1818; d. Sale, England, 11 October 1889)
physics.
Joule’s ancestors were Derbyshire yeomen; his grandfather had become wealthy as the founder of a brewery at Salford. James was the second of five children of Benjamin and Alice Prescott Joule. Together with his elder brother, James received his first education at home. From 1834 to 1837 the two brothers were privately taught elementary mathematics, natural philosophy, and some chemistry by John Dalton, then about seventy years old.
James never took part in the management of the4 brewery or engaged in any profession. He shared his father’s Conservative allegiance and entertained conventional Christian beliefs. He married Amelia Grimes, of Liverpool, in 1847, but she died in 1854. He spent the rest of his life with his two children in various residences in the neighborhood of Manchester. He had a shy and sensitive disposition, and his health was delicate.
Joule’s pioneering experiments were carried out in laboratories he installed at his own expense in his successive houses (or in the brewery). Later, owing to financial losses, he could no longer afford to work on his own and received some subsidies from scientific bodies for his last important investigations. His friends eventually procured him a pension from the government, in 1878, but by then his mental powers had begun to decline. He died after a long illness.
Joule’s scientific career presents two successive periods of very different character. During the decade 1837-1847, he displayed the powerful creative activity that led him to the recognition of the general law of energy conservation and the establishment of the dynamical nature of heat. After the acceptance by the scientific world of his new ideas and his election to the Royal Society (1850), he enjoyed a position of great authority in the growing community of scientists.
Joule carried on for almost thirty years a variety of skillful experimental investigations; none of them, however, was comparable to the achievements of his youth. His insufficient mathematical education did not allow him to keep abreast of the rapid development of the new science of thermodynamics, to the foundation of which he had made a fundamental contribution. Here Joule’s fate was similar to that of his German rival Robert Mayer. By the middle of the century, the era of the pioneers was closed, and the leadership passed to a new generation of physicists who possessed the solid mathematical training necessary to bring the new ideas to fruition.
Joule began independent research at the age of nineteen under the influence of William Sturgeon, a typical representative of those amateur scientists whose didactic and inventive activities were supported by the alert tradesmen of the expanding industrial cities of England. Taking up Sturgeon’s interest in the development of electromagnets and electromagnetic engines, the young Joule at once transformed a rather dilettantish effort into a serious scientific investigation by introducing a quantitative analysis of the “duty,” or efficiency, of the designs he tried. This was a far from trivial step, since it implied defining, for the various magnitudes involved, the standards and units that were still almost entirely lacking in voltaic electricity and magnetism. Joule’s preoccupation with this fundamental aspect of physical science is apparent throughout his work and culminated with the precise determination of the mechanical equivalent of heat.
At first Joule was so far removed from any idea of equivalence between the agencies of nature that for a while he hoped that electromagnets could become a source of indefinite mechanical power. He found their mutual attraction to be proportional to the square of the intensity of the electric current, whereas the chemical power necessary to produce the current in the batteries was simply proportional to the intensity. But he soon learned of the counter-induction effect discovered by M. H. Jacobi, which set a limit to the efficiency of electromagnetic engines. Subjecting the question to quantitative measurement, he realized, much to his dismay, that the mechanical effect of the current would always be proportional to the expense of producing it, and that the efficiency of the electromagnetic engines that he could build would be much lower than that of the existing steam engines. He presented this pessimistic conclusion in a public lecture (1841) at the Victoria Gallery in Manchester (one of Sturgeon’s short-lived educational ventures).
Joule’s early work, although rather immature, exhibited features that persisted in all his subsequent investigations and that unmistakably revealed Dalton’s influence. Adopting Dalton’s outlook, Joule believed that natural phenomena are governed by “simple” laws. He designed his experiments so as to discriminate among the simplest relations which could be expected to connect the physical quantities describing the effect under investigation; in fact, the only alternative that he ever contemplated was between a linear or a quadratic relation. This explains the apparent casualness of his experimental arrangements, as well as the assurance with which he drew sweeping conclusions from very limited series of measurements. In the search for simple physical laws, Joule necessarily relied on theoretical representations. We find the first explicit mention of these in the Victoria Gallery lecture, where Joule operated with a crude, but quite effective, atomistic picture of matter. His views embodied then-current ideas about the electric nature of the chemical forces and the electrodynamic origin of magnetization, as well as the concept of heat as a manifestation of vibratory motions on the atomic scale.
Abandoning hope of exploiting electric current as a source of power, Joule decided to study the thermal effects of voltaic electricity. Indirect evidence strongly suggests that this choice was motivated by the wish to enter a field of investigation made “respectable” by Faraday’s example. Yet whatever expectations he had in this respect were quickly dashed by the Royal Society’s frigid reception of his first paper and he turned again to the more sympathetic audience he found in the Manchester Literary and Philosophical Society.
Joule derived the quantitative law of heat production by a voltaic current—its proportionality with the square of the intensity of the current and with the resistance—from a brief series of measurements of the simplest description: he dipped a coiled portion of the circuit into a test tube filled with water and ascertained the slight changes of temperature of the water for varying current intensity and resistance (December 1840). The critical step in these, as well as in all his further experiments, was the measurement of small temperature variations; Joule’s success crucially depended on the use of the best available thermometers, sensitive to about a hundredth of a degree. To outsiders, who could not be aware of his extraordinary skill and accuracy, and failed to appreciate the logic underlying the design of his experiments, Joule’s derivation of statements of utmost generality from a few readings of minute temperature differences was bound to appear too rash to be readily trusted. Joule’s self-confidence may be understood only by realizing that his experimental work was deliberately directed toward testing the theoretical conceptions gradually taking shape in his mind.
During the next two years Joule made a systematic study of all the thermal effects accompanying the production and passage of the current in a voltaic circuit. From this study, completed by January 1843, he obtained a clear conception of an equivalence between each type of heat production and a corresponding chemical transformation or resistance to the passage of the current. Regarding the nature of heat, no conclusion could be derived from the phenomena of the voltaic circuit: voltaic electricity was “a grand agent for carrying, arranging and converting chemical heat”; but this heat could either be some substance simply displaced and redistributed by the current, or arise from modifications of atomic motions inseparable from the flow of the current.
Joule saw the possibility of settling this last question —and at the same time of subjecting the equivalence idea to a crucial test—by extending the investigation to currents not produced by chemical change but induced by direct mechanical effect. This brilliant inference led him to the next set of experiments, among the most extraordinary ever conceived in physics. He enclosed the revolving armature of an electromagnetic engine in a cylindrical container filled with a known amount of water and rotated the whole apparatus during a given time between the poles of the fixed electromagnet, ascertaining the small change of temperature of the water; the heat produced in this way could only be dynamical in origin. Moreover, by studying the heating effects of the induced current, to which a voltaic one was added or subtracted, he established, by a remarkably rigorous argument, the strict equivalence of the heat produced on revolving the coil and the mechanical work spent in the operation. He thus obtained a first determination of the coefficient of equivalence (1843).
After this accomplishment, his last series of experiments concerned with the mechanical equivalent of heat—those described in every elementary textbook —appear rather pedestrian by comparison, although they offer further examples of Joule’s virtuosity as an experimenter. They consist in direct measurements of the heat produced or absorbed by mechanical process: the expansion and compression of air (1845) and the friction of rotating paddle wheels in water and other liquids (1847). The experiments with air are of special interest because they were based on the same argument used by Mayer in his own derivation of the equivalent (letter to Baur, September 1841). But while Joule performed all the necessary experiments himself, Mayer made an extremely skillful use of available experimental results—most notably the difference of the specific heats at constant pressure and constant volume, and Gay-Lussac’s little-known demonstration (1806) that if a gas expands without doing work, its temperature remains constant. This law (which, strictly speaking, applies only to ideal gases) is usually ascribed to Joule—not without justification, since his experiment was much more accurate than Gay-Lussac’s.
Joule did not announce his momentous conclusions to a wider audience before he had completed single- handed all his painstaking measurements. Significantly, he did not venture outside his familiar Manchester environment. He simply gave a public lecture in the reading room of St. Ann’s Church (May 1847) and was content to have the text of his address published in the Manchester Courier (a newspaper for which his brother wrote musical critiques). This synthetic essay, entitled “On Matter, Living Force, and Heat,” gave the full measure of his creative imagination. In a few pages of limpid, straightforward description, he managed to draw a vivid picture of the transformation of “living force” into work and heat and to pass on to the kinetic view of the nature of heat and the atomic constitution of matter.
At the same time, he did not neglect to present a more technical account of his work before the scientific public. In particular, he reported his final determinations of the equivalent to the French Academy of Sciences, and presented this learned body with the iron paddle-wheel calorimeter he had used in the case of mercury. In contrast to previous occasions, Joule’s report to the British Association meeting at Oxford (June 1847) met with a lively response from the twenty-two-year-old William Thomson, an academically trained physicist who was better prepared than his elders to receive fresh ideas. How this dramatic encounter stimulated Thomson to formulate his own theory of thermodynamics is a story that no longer belongs to Joule’s biography. Indeed, the very moment of Joule’s belated recognition marked the end of his influence on scientific progress. Although Thompson had the highest regard for Joule’s experimental virtuosity, and repeatedly enlisted him in undertakings that required measurements of high accuracy, the scope of Thompson’s research was no longer within Joule’s full grasp.
The only substantial contribution to thermodnamics to which the joint names of Joule and Thomson, are attached belongs to an idea conceived by Thomson, who saw the possibility of analyzing the deviations of gas properties from the ideal behavior. In particular, a non-ideal gas, made to expand slowly through a porous plug (so as to approximate a specified mathematical condition—constant enthalpy), would in general undergo a cooling (essentially a transformation of atomic motion into work spent against the interatomic attractions). For the delicate test of this effect Thomson required Joule’s unsurpassed skill (1852). But the application of the Joule- Thomson effect to the technology of refrigeration belongs to a later stage in the development of thermodynamics.
In 1867 Joule was induced to carry out two high-precision determinations of the equivalent on behalf of the British Association Committee on Standards of Electrical Resistance. The first experiment, based on the thermal effect of currents, was designed by Thomson to test the proposed resistance standard. Because his result showed a 2 percent discrepancy from the original paddle-wheel calorimeter determination, Joule was asked to repeat the latter. He did so in painstaking experiments from 1875 to 1878 and fully confirmed his previous value. Joule’s results thus displayed the necessity of improving the resistance standard. This was Joule’s last contribution to the science his pioneering work had initiated.
BIBLIOGRAPHY
I. Original Works. See The Scientific Papers of James Prescott Joule, 2 vols. (London, 1884-1887).
II. Secondary Literature. Information on Joule may be found in Osborne Reynolds, “Memoir of James Prescott Joule,” in Memoirs and Proceedings of the Manchester Literary and Philosophical Society, 4th ser., 6 (1892); and J. C. Crowther, British Scientists of the Nineteenth Century (London, 1935), ch. 3.
L. Rosenfeld
James Prescott Joule
James Prescott Joule
The English physicist James Prescott Joule (1818-1889) proved that mechanical and thermal energies are interconvertible on a fixed basis, and thus he established the great principle of conservation of energy.
On Dec. 24, 1818, James Joule was born at Salford near Manchester, the second of the five children of a wealthy brewery owner. A rather frail boy, he received his early education at home. In 1839, in the laboratory in his home, he began his studies of electrical motor efficiency, which ultimately led to his development of the mechanical theory of heat. In connection with this work he became one of the first to realize the necessity for standard units in electricity and to advocate establishing them.
In the course of his efficiency experiments Joule made his first discovery—now known as Joule's law: the heating of a conductor depends upon its resistance and the square of the current passing through it. He presented this important generalization in a paper, "On the Production of Heat by Voltaic Electricity," before the Royal Society in London in 1840.
Joule's study of the interrelation of heat and electrical energy may have stimulated his study of the relationship between heat and mechanical work. His approach was direct: he used the mechanical energy provided by falling weights to heat water by stirring it and made precise measurements of the heat produced and the energy lost by these weights. The results provided the first value of the mechanical equivalent of heat, corresponding to a temperature increase of 1□F of 1 pound of water for the expenditure of 838 foot-pounds of work. The apparent simplicity of Joule's experiment is quite misleading, for enormous experimental skill, great care, and limitless patience were needed to get repeatable results; experts regard his work as demonstrating exceptional skill.
Joule presented the results of these mechanical work experiments in a paper, "On the Calorific Effects of Magneto-electricity and on the Mechanical Value of Heat," which he read at the meeting of the British Association in 1843, but no notice was taken of them. During the next 6 years, using variations in procedure, he continued his measurements and consistently substantiated his first results. His reports continued to be overlooked until 1847, when they came to the attention of William Thomson (later Lord Kelvin). He realized their significance, and through his efforts Joule finally got an attentive hearing of his work in 1849, when his paper "On the Mechanical Equivalent of Heat" was read to, and accepted for publication by, the Royal Society. His only other notable work, done with Thomson, led to the discovery of the so-called Joule-Thomson effect in 1862.
Joule remained an isolated amateur scientist for most of his life. After the death of his wife and young daughter in 1853, he lived in relative seclusion. Beginning about 1872 his health deteriorated. He died at his home in Sale, Cheshire, on Oct. 11, 1889.
Further Reading
James G. Crowther gives an excellent treatment of Joule in his British Scientists of the Nineteenth Century (1935). Alexander Wood, Joule and the Study of Energy (1925), merits reading.
Additional Sources
Cardwell, D. S. L. (Donald Stephen Lowell), James Joule: a biography, Manchester; New York: Manchester University Press; New York: Distributed exclusively in the USA and Canada by St. Martin's Press, 1989.
Cardwell, D. S. L. (Donald Stephen Lowell), James P. Joule, Manchester (97 Grovenor St., Manchester (M1 7HF)): North Western Museum of Science and Industry, 1978. □
James Prescott Joule
James Prescott Joule
1818-1889
English physicist who investigated the equivalence of mechanical, electrical, and heat energy, and who is often credited (together with Joseph Mayer) with formulating the law of conservation of energy. The unit of energy in the international system is named after Joule. Joule's family had acquired substantial wealth through a family-owned brewery, leaving him free to devote his time to scientific experiments, generally involving careful measurement of the heat energy released by different physical processes.