# James Clerk Maxwell

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## Maxwell, James Clerk

(klärk), 1831–79, great Scottish physicist. After a brilliant career at Edinburgh and Cambridge, where he won early recognition with mathematical papers, he was a professor at Marischal College, Aberdeen (1856–60), and at King's College, London (1860–65). In 1871 he was appointed the first professor of experimental physics at Cambridge, where he directed the organization of the Cavendish Laboratory. He is known especially for his work in electricity and magnetism, summarized in*A Treatise on Electricity and Magnetism*(1873). Basing his own study and research on that of Faraday

**Faraday, Michael**

, 1791–1867, English scientist. The son of a blacksmith, he was apprenticed to a bookbinder at the age of 14. He had little formal education, but acquired a store of scientific knowledge through reading and by attending educational lectures including, in

**.....**Click the link for more information. , he developed the theory of the electromagnetic field on a mathematical basis and made possible a much greater understanding of the phenomena in this field. He was led to the conclusion that electric and magnetic energy travel in transverse waves that propagate at a speed equal to that of light; light is thus only one type of electromagnetic radiation

**electromagnetic radiation,**

energy radiated in the form of a wave as a result of the motion of electric charges. A moving charge gives rise to a magnetic field, and if the motion is changing (accelerated), then the magnetic field varies and in turn produces an electric field.

**.....**Click the link for more information. . Maxwell's electromagnetic theory occupies a position in classical physics comparable to Newton's work on mechanics. One of his early papers, "On the Stability of Motion of Saturn's Rings" (1859), was especially important and foreshadowed his later investigations of heat and the kinetic theory of gases. He is also known for his studies of color (which led to his invention of the color disk named for him) and of color blindness, and wrote a classic elementary text in dynamics,

*Matter and Motion*(1876).

### Bibliography

See N. Forbes and B. Mahon, *Faraday, Maxwell, and the Electromagnetic Field* (2014).

## Maxwell, James Clerk

Born June 13, 1831, in Edinburgh; died Nov. 5, 1879, in Cambridge. British physicist, founder of classical electrodynamics and one of the founders of statistical physics. Member of the London Royal Society (1860). Son of a Scottish nobleman of the well-known Clerk clan.

Maxwell studied at the universities of Edinburgh (1847-50) and Cambridge (1850-54). From 1856 to 1860 he was a professor at Marischal College in Aberdeen, and from 1860 to 1865 at the University of London. In 1871 he became a professor at Cambridge University, where he founded the first specially equipped physics laboratory in Great Britain—the Cavendish Laboratory—of which he was director from 1871.

Maxwell’s scientific activities encompass numerous fields, including electromagnetism, the kinetic theory of gases, optics, and the theory of elasticity. Maxwell wrote his first work, *On the Description of Oval Curves and Those Having a Plurality of Foci*, before he was 15 (1846, published 1851). One of his first studies dealt with the physiology and physics of color perception and with colorimetry (1852-72). In 1861 he produced for the first time a color image by simultaneously projecting red, green, and blue diapositives on a screen, thus proving the validity of the three-component theory of color vision and simultaneously outlining the methods later used to develop color photography. He devised one of the first instruments for the quantitative measurement of color, which was called the Maxwell disk. In 1857-59 he conducted theoretical investigations of the stability of Saturn’s rings and showed that they can be stable only if they consist of disconnected solid particles.

Maxwell’s investigations of electricity and magnetism were set forth in the articles “On Faraday’s Lines of Force” (1855-56), “On Physical Lines of Force” (1861-62), and “A Dynamical Theory of the Electromagnetic Field” (1864) and in the two-volume fundamental work *Treatise on Electricity and Magnetism* (1873). In these works Maxwell mathematically developed the views of M. Faraday regarding the role of an intermediate medium in electric and magnetic interactions. He unsuccessfully attempted (after Faraday) to interpret this medium as a pervasive, universal ether. The subsequent development of physics showed that the electromagnetic field, the theory of which (in classical physics) Maxwell created, is the carrier of electromagnetic interactions. In this theory Maxwell summarized all known facts of macroscopic electrodynamics and introduced for the first time the concept of displacement current, which, like an ordinary current (conduction current or moving electric charges), generates a magnetic field. Maxwell expressed the laws of the electromagnetic field by a system of four partial differential equations. The general and exhaustive nature of these equations was evident from the fact that their analysis made possible the prediction of many then unknown phenomena and principles. For example, the existence of electromagnetic waves, which subsequently were discovered experimentally by H. Hertz, was deduced from the equations. In investigating these equations, Maxwell concluded that light has an electromagnetic nature (1865) and showed that the velocity of any other electromagnetic wave in a vacuum is equal to the velocity of light. He measured (with greater accuracy than W. Weber and F. Kohlrausch in 1856) the ratio of the electrostatic unit charge to the electromagnetic unit charge and confirmed its equality to the velocity of light. It followed from Maxwell’s theory that electromagnetic waves produce pressure. Light pressure was established experimentally in 1899 by P. N. Lebedev.

Maxwell’s theory of electromagnetism was eventually experimentally confirmed and has become a generally recognized classical foundation of modern physics. A. Einstein clearly characterized the role of this theory: “Then came the great change, which will be associated for all times with the names Faraday, Maxwell, and Hertz. The lion’s share in this revolution fell to Maxwell. … After Maxwell they [people] conceived physical reality as represented by continuous fields, not mechanically explicable. … This change in the conception of reality is the most profound and fruitful one that has come to physics since Newton” *(Sobr. nauch. trudov*, vol. 4, Moscow, 1967, p. 138).

In his studies of the molecular kinetic theory of gases—the articles “Illustrations of the Dynamical Theory of Gases” (1860) and “On the Dynamical Theory of Gases” (1866)—Maxwell solved the statistical problem of the velocity distribution of the molecules of an ideal gas. Maxwell calculated the dependence of the viscosity of a gas on the velocity and on the mean free path of the molecules (1860) by calculating the absolute value of this path, and he derived a number of important thermodynamic relations (1860). He experimentally measured the coefficient of viscosity of dry air (1866). In 1873-74 he discovered the phenomenon of double refraction in viscous liquids (the Maxwell effect).

Maxwell also wrote works for the general reader, including a number of articles for the *Encyclopaedia Britannica* and such popular books as *The Theory of Heat* (1870), *Matter and Motion* (1873), and *Electricity in an Elementary Presentation* (1881), all of which have been translated into Russian. Maxwell’s publication of H. Cavendish’s manuscripts on electricity (1879) with extensive commentary constituted an important contribution to the history of physics.

### WORKS

*The Scientific Papers*, vols. 1-2. Cambridge, 1890.

*Theory of Heat*. London, 1871.

*A Treatise on Electricity and Magnetism*, vols. 1-2. Oxford, 1873.

*In Russian translation*:

*Izbr. soch. po teorii elektromagnitnogo polia*. Moscow, 1954.

*Stat’i i rechi*. Moscow, 1968. (Contains a bibliography of Maxwell’s works and of works about Maxwell.)

### REFERENCES

MacDonald, D.*Faradei, Maksvell i Kel’vin*. Moscow, 1967. (Translated from English.)

Campbell, L., and W. Garnett.

*The Life of J. C Maxwell*London, 1882.

IA. G. DORFMAN