He discovered that an intense magnetic field could rotate the plane of polarized light, a phenomenon known today as the Faraday effect. In conjunction with these experiments, he showed that all matter conducts the magnetic line of force. Objects that were good conductors he called paramagnetics, while those that 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. Faraday died in London on August 25, 1867.

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.