James Prescott Joule (24 December 1818, Salford, Lancashire, England, United Kingdom - 11 October 1889, Sale, Cheshire, England, United Kingdom) was an English physicist who made significant contributions to the formation of thermodynamics. Based on experiments, the law of conservation of energy. He established a law that determines the thermal effect of an electric current. He calculated the velocity of the gas molecules and established its dependence on temperature.
Experimentally and theoretically studied the nature of heat and found its connection with mechanical work, resulting in almost simultaneously with Mayer came to the concept of universal conservation of energy, which, in turn, provided the formulation of the first law of thermodynamics. He worked with Thomson on the absolute temperature scale, described the phenomenon of magnetostriction, discovered the connection between the current flowing through a conductor with a certain resistance and the amount of heat released at the same time (Joule — Lenz law). He made a significant contribution to the technique of physical experiment, improved the design of many measuring devices.
A unit of energy, the Joule, is named after the Joule. Born into the family of a wealthy brewery owner in Salford near Manchester, he was educated at home, and for several years his teacher in elementary mathematics, chemistry and physics was Dalton. From 1833 (from the age of 15) he worked at the brewery, and, in parallel with training (up to 16 years) and science classes until 1854 he participated in the management of the enterprise, until it was sold.
The first experimental studies began in 1837, interested in the possibility of replacing steam engines at the brewery on electric. In 1838, on the recommendation of one of his teachers, Davis, whose close friend was the inventor of the electric motor Sturgeon, published the first work on electricity in the scientific journal Annals of Electricity, organized the year before by Sturgeon, the work was devoted to the device of the electromagnetic motor. In 1840 he discovered the effect of magnetic saturation during magnetization of ferromagnets, and during 1840-1845 he experimentally studied electromagnetic phenomena.
In 1841, James Joule discovered the law named after him, which establishes a quadratic relationship between the current strength and the amount of heat released by this current in the conductor (in Russian literature it appears as the Joule — Lenz law, since 1842 this law was discovered by the Russian physicist Lenz). The discovery was not appreciated by the Royal society of London, and the work was published only in the periodical of the Manchester literary and philosophical society
In 1840, Sturgeon moved to Manchester and headed the Gallery of practical knowledge-a commercial exhibition and educational institution, where in 1841 he invited Joule as the first lecturer.
In the works of the early 1840s he investigated the economic feasibility of electromagnetic motors, initially believing that electromagnets could be the source of an unlimited amount of mechanical work, but soon became convinced that from a practical point of view the steam engines of the time were more efficient, publishing in 1841 the conclusions that the efficiency of the" ideal " electromagnetic engine per 1 pound of zinc (used in batteries) is only 20% of the efficiency of the steam engine per 1 pound of coal burned, without hiding his disappointment.
In 1842, he discovered and described the phenomenon of magnetostriction, which consists in changing the size and volume of a body with a change in its state of magnetization. In 1843 he formulated and published the final results of the work on the study of heat in conductors, in particular, experimentally shows that the heat emitted is in no way taken away from the environment, which irrevocably refuted the theory of hydrogen, the supporters of which still remained at that time. In the same year became interested in the General problem of quantitative ratio between different forces, leading to the generation of heat, and after coming to belief in the existence predicted by Mayer (1842) a particular relationship between work and quantity of heat, looking for the ratio between these values, the mechanical equivalent of heat. During the years 1843-1850 he conducted a series of experiments, continuously improving the experimental technique and each time confirming the principle of conservation of energy with quantitative results.
In 1844, the Joel family moved to a new home in Wally Range where a comfortable laboratory was equipped for James. In 1847 he married Amelia Grimes, soon they had a son and a daughter, in 1854 Amelia Joule died.
In 1847, he met with Thomson, who gives a high assessment of the experimental technique of Joule, and with whom he later collaborated fruitfully, largely under the influence of Joule, Thomson's views on the questions of molecular kinetic theory were formed. In the first joint works Thomson and Joule create a thermodynamic temperature scale.
In 1848, to explain the thermal effects of increasing pressure, he proposed a model of gas as consisting of microscopic elastic balls, the collision of which with the walls of the vessel and creates pressure, and giving an estimate of the speed of" elastic balls " of hydrogen about 1850 m/c. On the recommendation of Clausius, this work was published in the Philosophical transactions of the Royal society, and although it subsequently revealed serious flaws, it had a significant impact on the formation of thermodynamics, in particular, ideologically echoes the work of PoE van der Waals in the early 1870s on the modeling of real gas.
By the end of the 1840s, Joule's work was widely recognized in the scientific community, and in 1850 he was elected a full member of the Royal society of London.
In the works of 1851, perfecting his theoretical models of representing heat as the motion of elastic particles, he calculated the heat capacity of some gases quite accurately. In 1852 he discovered, measured and described in a series of joint works with Thomson the effect of changes in gas temperature during adiabatic throttling, known as the Joule — Thomson effect, which later became one of the main methods for obtaining ultra-low temperatures, thereby contributing to the emergence of low temperature physics as a branch of natural science.
In the 1850s he published a large series of articles on the improvement of electrical measurements, offering designs of voltmeters, galvanometers, ammeters, providing high accuracy of measurements; in General, throughout his scientific practice, Joule paid considerable attention to experimental techniques, allowing to obtain high-precision results.
In 1859 he investigated the thermodynamic properties of solids, measuring the thermal effect during deformation, and noted the non-standard properties of rubber in comparison with other materials.
In the 1860s he was interested in natural phenomena, offering possible explanations of the nature of atmospheric thunderstorms, mirages, meteorites.
In 1867 Joule according to the scheme proposed by Thomson holds for the British science Association for the measurement of the mechanical equivalent of heat, but gets results at variance with the values resulting from purely mechanical experiments, but the clarification of the terms of the mechanical experiments have confirmed the accuracy of the measurements Joule in 1878 impedance standard was revised.
In the initial stages of activity Joule put experiments and engaged in research solely on their own funds, but after the sale of the brewery in 1854, the financial situation gradually deteriorated, and had to use the funding of various scientific organizations, and in 1878 appointed a state pension. Since childhood, he suffered from a disease of the spine, and since the early 1870s, due to poor health, he practically did not work. He died in 1889.
Mechanical equivalent of heat
Starting in 1843, Joule seeks confirmation of the principle of conservation of energy and tries to calculate the mechanical equivalent of heat. In the first experiments, he measures the heating of the liquid in which the solenoid with an iron core is immersed, rotating in the field of the electromagnet, making measurements in the cases of closed and open winding of the electromagnet, then improves the experiment, excluding manual rotation and driving the electromagnet with a descending load. According to the results of measurements, he formulates and publishes the results of experiments in 1843 in the article "on the thermal effect of magnetoelectricity and the mechanical value of heat". In 1844, he formulated the first version of the law of heat capacity of complex crystalline bodies, known as the Joule-Kopp law (Kopp in 1864 gave an exact formulation and final experimental confirmation).
Further, in the experience of 1844 measures the heat generated by forcing liquid through a narrow tube, in 1845, is a measure of heat as the gas is compressed, and the experience of 1847 compares the costs for the rotation of the stirrer in the liquid with the resulting frictional heat.
In the works of 1847-1850 gives an even more accurate mechanical equivalent of heat. They used a metal calorimeter mounted on a wooden bench. Inside the calorimeter was an axis with blades arranged on it. On the side walls of the calorimeter were rows of plates that prevented the movement of water, but did not touch the blades. On the axis outside the calorimeter was wound a thread with two dangling ends, to which the weights were attached. The experiments measured the amount of heat released when the axis rotates due to friction. This amount of heat was compared with the change in the position of the loads and the force acting on them.
Evolution of the values of the mechanical equivalent of heat obtained in the Joule experiments (in foot-pounds or foot-pound-force per British thermal unit):
838 (4,51 Дж/кал), 1843;
770 (4,14 Дж/кал), 1844;
823 (4,43 Дж/кал), 1845
819 (4,41 Дж/кал), 1847
772,692 (4,159 Дж/кал), 1850.
The latter estimate is close to the ultra-accurate measurements made in the twentieth century.
The struggle for priority in the discovery of the law of energy conservation
The second half of the 1840-ies in the "Proceedings of the French Academy of Sciences" a fierce debate about priority in the discovery of the law of conservation of energy for thermodynamic systems between Joule and Mayer, and although the publication of Meyer's came out a little before, he being a doctor by profession, he was not taken seriously, whereas the Joule is already supported by a large physics, in particular his report of 1847 the British science Association has received high marks attended the meeting of the Faraday, Stokes, and Thomson. Timiryazev, later reviewing this debate, noted the consistency of Mayer's argument in the fight against the"petty jealousy of shop scientists." Helmholtz, who published the principle of conservation of energy in 1847, in 1851 drew attention to the work of Mayer, and in 1852 openly recognized his priority.
The next round of struggle for priority occurred in the 1860s, when the law received universal recognition in the scientific community. Tyndall in 1862 in a public lecture shows the priority of Mayer, and his point of view becomes Clausius. Thet, known Pro-British Patriotic views, in a series of publications insists on the priority of Joule, not recognizing the work of Mayer 1842 physical content, he opposes Clausius, and the philosopher during, while belittling the value of the works of Joule and Helmholtz, actively insists on the priority of Mayer, which largely served as the final recognition of the priority of Mayer.
Recognition and memory
In 1850 he was elected a fellow of the Royal society of London. In 1852, for his work on the quantitative equivalent of heat, he was awarded the first Royal medal. In 1860 he was elected honorary President of the Manchester literary and philosophical society).
He received the degrees of doctor of laws of Trinity College Dublin (1857), doctor of civil law of the University of Oxford (1860), doctor of laws (LL.D.) of the University of Edinburgh (1871).
In 1866 Joule was awarded the Copley medal, in 1880 the albert medal. In 1878 he was granted a lifetime pension of 215 pounds by the government.
In 1872 and 1877 he was twice elected President of the British scientific Association .
At the second international Congress of electricians, held in 1889 — the year of Joule's death, a unified unit of measurement of work, energy, amount of heat was named after him, for which the coefficient of transition between mechanical work and heat (mechanical equivalent of heat) was not required, which became one of the derived SI units with its own name.
In Manchester city hall there is a monument to Joel by the sculptor Alfred Gilbert opposite the monument to Dalton.
In 1970, the international astronomical Union named a crater on the far side of the moon after James Joule.