Exercises

I. Word-study.

Say what is meant by

II. Comprehension check-up.

1) Agree or disagree with the following statements.

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2) Say as much as you can on:

a) personal life

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III. Divide the text into logical parts and state the general idea of each part. James clerk maxwell (1831-1879)

James Clerk Maxwell was mathematically-trained Scottish electrician and physicist who substantially influenced the development of Fara­day's field theory of electromagnetism. Born in 1831 in Edinburgh, Maxwell enrolled at Edin­burgh University at age 16 and was acquainted with a number of prominent Scottish scien­tists from an early age, including Kelvin, James David Forbes, and Peter Guthrie Tait. At the age of 14, he developed a new geometrical method of generating perfect oval curves, pub­lishing his results with the help of Forbes in the Proceedings of the Royal Society of Edinburgh for 1846. After election to fellowship at Trinity College, Cambridge in 1855 he began teaching hydrostatics and optics, but returned to Scotland to teach at Marischal College in Aberdeen in 1856. In 1860, he was appointed to a professorship at King's College, London.

When the Cambridge Cavendish Laboratory opened in 1871, Maxwell was invited to serve as the first Cavendish Professor of Physics after Kelvin and Helmholtz had declined the position. Maxwell personally designed the equipment and instrumentation and heavily influenced the research program of the laboratory. Maxwell completed his frequently reprinted Treatise on Heat in the same year, and published his widely read textbook Treatise on Electricity and Magnetism in 1873. He also edited the electrical papers of Henry Cavendish (1879). Maxwell contributed several scientific articles containing considerable technical detail, such as "Constitution of Bodies," "Diffusion," and "Atom," etc., to the ninth edition of the Encyclopaedia Britannica, which he co-edited with T.H. Huxley. These articles were reprinted in the 1890 Cambridge edition of Maxwell's Scientific Papers. He also published substantial research on thermodynamics, the molecular theory of gases, colour vision and theoretical work on the rings of Saturn. Using his colour theory, he produced the first colour photograph in 1861 by projection through coloured filters.

In order to illustrate principles of diffusion and gas thermodynamics, Maxwell invented the celebrated thought experiment "Maxwell's Demon," which Kelvin (who gave the demon its name) described as "a creature of imagination having certain perfectly well-defined powers of action, purely mechanical in their character, invented to help us to under­stand the 'Dissipation of Energy' in nature". With the demon, Maxwell demonstrated that the Second Law of Thermodynamics, which supports the obser­vation that heat naturally flows from hot to cold bodies, could only be true statistically, since in individual molecular collisions, hot bodies can derive heat from colder ones.

Maxwell's work on electromagnetism can be viewed in many respects as a mathematizarion and elaboration of ideas advanced by Faraday's experimental work, and illustrates a crucial point in nineteenth-century physics when natural language and the language of mathematics in describing physical phenomena parted company; for example, in his paper "On Faraday's Lines of Force" (1855), Maxwell sought to express mathematically (using an analogy to fluid flow) Faraday's graphical observation of curvilinear magnetic forces operating along lines of iron filings scattered on paper and under the influence of magnets. Upon reading Maxwell's papers, Faraday wrote to Maxwell, "when a mathematician engaged in investigating physical actions and results has arrived at his conclusions, may they not be expressed in common lan­guage as fully, clearly and definitely as in mathematical formulae?". Maxwell later wrote in the Treatise on Electricity and Magnetism, did not feel called upon either to force his results into a shape acceptable to the mathematical taste of the time, or to express them in a form which mathematicians might attack ... it is mainly in the hope of mak­ing these ideas the basis of a mathematical method that I have undertaken this treatise". "Maxwell's equations," as they have been called after refinement by Oliver Heaviside and Heinrich Hertz, were developed to understand the relationship between electrical and mag­netic phenomena in magnetic and electrical fields. The equations grew out of Maxwell's con­tinuing attempts to describe Faraday's fields mathematically. The mechanical properties of the rotating vortices—such as their angular velocity and defor­mation—could explain by analogy many magnetostatic, electrostatic, electrodynamic, and magnetodynamic effects. Maxwell's model eventually accounted for all of the then-known experimentally derived laws of electricity and magnetism, and predicted others.

Faraday had demonstrated that a magnetic field could shift the plane of polarization of light (the Faraday Effect) suggesting a link between light and magnetism. Maxwell discovered wave properties in his mechanical field model and further found that he could describe light as the elastic displacement of the medium describing transverse shear waves. In his 1864 paper entitled "A Dynamic Theory of the Electromagnetic Field," of which Part VI "Elec­tromagnetic Theory of Light" is reproduced below, Maxwell working from his model hypoth­esized that light was an electromagnetic wave disturbance propagating through a field. He found that his calculation for the velocity of propagation of these transverse waves in the ether closely matched the experimentally measured velocity of light.

Although there were many researchers working in the field of elec-tromagnetism at the same time as Maxwell, such as Hermann Helmholtz, Michael Faraday, Hendrik Lorentz, Ludwig Boltzmann, and Wilhelm Eduard Weber, Maxwell's work still stands out as highly original: it is difficult to conceive of modern electronic technology such as radio, television, microwave transmission, or even the atomic bomb without Maxwell's insights. In order to reduce transcription errors, the selection below has been reproduced in photographic facsimile from the 1890 edition of Maxwell's collected papers.