Background

James Prescott Joule was born on December 24, 1818, on New Bailey Street in Salford, Manchester, England. His ancestors were Derbyshire yeomen; his grandfather had become wealthy as the founder of a brewery at Salford. Joule was the second of five children of Benjamin Joule, also a brewer, and Alice Prescott.

Education

Together with his elder brother, Joule 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. Engineers Peter Ewart and Eaton Hodgkinson also influenced them greatly. Joule was fascinated by electricity, and he and his brother experimented by giving electric shocks to each other and to the family's servants.

Career

Joule never took part in the management of the brewery or engaged in any profession. His 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.

Joule’s scientific career presents two successive periods of a 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, 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.

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.

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 processes: 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. 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. 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 Thomson had the highest regard for Joule’s experimental virtuosity and repeatedly enlisted him in undertakings that required measurements of high accuracy, the scope of Thomson’s research was no longer within Joule’s full grasp.

The only substantial contribution to thermodynamics 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, would in general undergo a cooling. 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.

Joule served as President of Manchester Literary and Philosophical Society in 1860, and as President of the British Association for the Advancement of Science in 1872 and 1887.

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.

Achievements

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  James Prescott Joule is remembered today for his studies of the nature of heat. He proved that mechanical and thermal energies are interconvertible on a fixed basis, and thus he established the great principle of conservation of energy. He discovered Joule's first law in 1841, that the heat which is evolved by the proper action of any voltaic current is proportional to the square of the intensity of that current, multiplied by the resistance to conduction which it experiences. He also is connected with disproving caloric theory. Now the value of the mechanical equivalent of heat is generally represented by the letter J, and a standard unit of work is called the joule.
  
  Joule's many honors and commendations include the Royal Medal (1852) "for his paper on the mechanical equivalent of heat," the Copley Medal (1870) "for his experimental researches on the dynamical theory of heat," the Albert Medal of the Royal 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"; honorary Doctor of Law degrees from Trinity College (1857) and the University of Edinburgh (1871), and honorary Doctor of Civil Law degree from the University of Oxford (1860).
  
  There is a memorial to Joule in the north choir aisle of Westminster Abbey. A statue of Joule by Alfred Gilbert stands in Manchester Town Hall, opposite that of Dalton.
  
  The Wetherspoon's pub in Sale, the town of his death, is named "The J. P. Joule" after him. Joule's family brewery survives to this day but is now located in Market Drayton.

Works

More photos

• book

  • Joint Scientific Papers Of Joule 1884
  • Das Mechanische Wärmeäquivalent 1872
  • On the thermal effects of fluids in motion 1860
  • New Determination Of The Mechanical Equivalent Of Heat 1878

• Invention

  • Electric motor

    (An electric motor presented to Kelvin by James Joule in 1...)

    1842

  • Heat Apparatus

    (Joule's Heat Apparatus.)

    1845

Religion

Joule shared his father’s Conservative allegiance and entertained conventional Christian beliefs.

Views

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.

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.

Membership

Joule was elected a Fellow to the Royal Society in 1850. He was also a foreign associate of the National Academy of Sciences, and foreign member of the American Academy of Arts and Sciences and the Academy of Sciences of Turin.

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  Fellow

  Royal Society , United Kingdom

  1850

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  Foreign associate

  National Academy of Sciences , United States

• 

  Foreign member

  American Academy of Arts and Sciences , United States

• 

  Foreign member

  Academy of Sciences of Turin , Italy

Personality

Joule had a shy and sensitive disposition.

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.

Physical Characteristics: Joule's health was rather delicate.

Connections

Joule married Amelia Grimes of Liverpool in 1847. They had three children together: a son, Benjamin Arthur Joule, a daughter, Alice Amelia, and another son, Henry, who died when he was only three weeks old. Amelia died in 1854, 7 years after the wedding. Joule spent the rest of his life with his two children in various residences in the neighborhood of Manchester.

Father:

Benjamin Joule

Mother:

Alice Prescott

Spouse:

Amelia Grimes

Son:

Benjamin Arthur Joule

Daughter:

Alice Amelia Joule

teacher:

John Dalton

teacher:

Peter Ewart

teacher:

Eaton A. Hodgkinson

opponent:

Robert Mayer

References

• Dictionary of Scientific Biography, Volume 7
  1973
• Biography of James Prescott Joule
  2007
• Men of science
  1936