FARADAY'S DISCOVERY

Although for certain purposes we still employ batteries to a limited extent to generate the electric current, the usual procedure today is by electromagnetic induction. Great genera­tors in our power stations, driven by powerful turbines, oper­ate through the relative movement of conductors and magnets on a principle discovered in 1831 by that remarkable man, Michael Faraday.

A bookbinder's apprentice in London, Faraday was a clever boy. In the early part of 1812 he was given tickets to hear a course of lectures by Humphry Davy at the Royal Institution. At the end of the course he wrote up his notes on the lectures, bound them and sent them to the lecturer with a request that he should be employed as assistant. A few months later, at the age of twenty-two Michael Faraday was appointed to a post at the Royal Institution at 25 shillings a week. Thus, he started on that remarkable career which lasted for nearly half a century, during which he laid the founda­tions for much of our present electrical age. He became a skilful experimenter and an enthusiastic lecturer.

During the ten years or so before his great discovery, many investigators had interested themselves in the connection be­tween electricity and magnetism. It had been definitely established by Oersted's experiment that magnetism could be produced from the electric current. Why, then, could not the process be reversed and the electric current produced from magnetism?

The fulfillment of Faraday's hopes came in the year 1831 as a result of his experiments in the laboratory at the Royal Institution. We can read in his "Laboratory Notes" how, day by day, he carried on different experiments with wire and coils, permanent bar magnets and magnetic needles, with varying results.

On October 17, 1831, he discovered that if he had a coil of wire connected to a galvanometer and inserted a magnet into the coil, he obtained a deflection on the galvanometer. The coil consisted of eight windings of copper wire each 27 feet long, the windings being connected in parallel. When he was inserting one end of the magnet into the coil, he noticed that the deflection of the galvanometer continued only for a short time and stopped as soon as the magnet was completely inserted. No current was generated while the magnet remained stationary. When it was taken away, there was a second gal­vanometer deflection, but this time in the reverse direction. In both cases, however, there was a current only during the time that the magnet was moving.