The English physicist and chemist Michael Faraday (1791-1867) discovered benzene and the principles of current induction.

One of a blacksmith's 10 children, Michael Faraday was born on Sept. 22, 1791, in Newington, Surrey. The family soon moved to London, where young Michael picked up the rudiments of reading, writing, and arithmetic. At the age of 14 he was apprenticed to a bookbinder and bookseller. He read ravenously and attended public lectures, including some by Sir Humphry Davy.

Faraday's career began when Davy, temporarily blinded in a laboratory accident, appointed Faraday as his assistant at the Royal Institution. With Davy as a teacher in analytical chemistry, Faraday advanced in his scientific apprenticeship and began independent chemical studies. By 1825 he discovered benzene and had become the first to describe compounds of chlorine and carbon. He adopted the atomic theory to explain that chemical qualities were the result of attraction and repulsion between united atoms. This proved to be the theoretical foundation for much of his future work.

Faraday had already done some work in magnetism and electricity, and it was in this field that he made his most outstanding contributions. His first triumph came when he found a solution to the problem of producing continuous rotation by use of electric current, thus making electric motors possible. Hans Oersted had discovered the magnetic effect of a current, but Faraday grasped the fact that a conductor at rest and a steady magnetic field do not interact and that to get an induced current either the conductor or the field has to move. On Aug. 29, 1831, he discovered electromagnetic induction.

During the next 10 years Faraday explored and expanded the field of electricity. In 1834 he announced his famous two laws of electrolysis. Briefly, they state that for any given amount of electrical force in an electrochemical cell, chemical substances are released at the electrodes in the ratio of their chemical equivalents. He also invented the voltameter, a device for measuring electrical charges, which was the first step toward the later standardization of electrical quantities.

Faraday continued to work in his laboratory, but his health began to deteriorate and he had to stop work entirely in 1841. Almost miraculously, however, his health improved and he resumed work in 1844. He began a search for an interaction between magnetism and light and in 1845 turned his attention from electrostatics to electromagnetism. He discovered that an intense magnetic field can rotate the plane of polarized light, a phenomenon known today as the Faraday effect. In conjunction with these experiments he showed that the magnetic line of force is conducted by all matter. Those which were good conductors he called paramagnetics, while those which conducted the force poorly he named diamagnetics. Thus, the energy of a magnet is in the space around it, not in the magnet itself. This is the fundamental idea of the field theory.

Faraday was a brilliant lecturer, and through his public lectures he did a great deal to popularize science. Shortly after he became head of the Royal Institution in 1825, he inaugurated the custom of giving a series of lectures for young people during the Christmas season. This tradition has been maintained, and over the years the series have frequently been the basis for fascinating, simply written, and informative books.

On Aug. 25, 1867, Faraday died in London.

The admiration of physicists for Faraday has been demonstrated by naming the unit of capacitance the farad and a unit of charge, the faraday. No other man has been doubly honored in this way. His name also appears frequently in connection with effects, laws, and apparatus. These honors are proper tribute to the man who was possibly the greatest experimentalist who ever lived.

Further Reading

• Much has been written about Faraday, but the student should first read the account by his successor at the Royal Institution, John Tyndall, Faraday as a Discoverer (1961). The sketch of Faraday in James Gerald Crowther, Men of Science (1936), is also recommended. Leslie Pearce Williams, Michael Faraday: A Biography (1965), appraises Faraday's work in relation to modern science and contains many previously unpublished manuscripts.