A few words on the connection between electricity and magnetism

To-day, the connection between electricity and magnetism is so widely recognized and seems to be so obvious that it is a little difficult to understand why it should for so long have remained suspected but not proved. For centuries, philosophers and physicists had been familiar with magnets of the natural kind and by the beginning of the nineteenth century had already been able to produce powerful "artificial" magnets.

If we were asked to-day to prove the existence of a connection between electricity and magnetism, we could not do better than point to the electromagnet. It is the flow of current in the conductor of that device which produces a magnetic effect. The electromagnet, however, was unknown at the beginning of the nineteenth century. It could hardly have been invented before Volta, in 1800, constructed his pile and provided a means of obtaining a steady continuous flow of current. Even then its invention was delayed for a rather long period of time.

In 1820, the Danish physicist, Oersted, discovered almost by accident that a current flowing in a wire lying parallel with an adjacent magnetic needle caused that needle to deflect away from its normal north-and-south alignment. He also discovered that the direction of the deflection, to the east or to the west, depended both upon the direction of the current in the conductor and upon the position of the conductor, above or below the needle. It was a momentous discovery because of the stimulus which it immediately gave to the study of the long-suspected connection between electricity and magnetism.

Inspired directly by Oersted's discovery, the French physicist, Arago, produced, at last, a prototype of the modern electromagnet. He was among the first, if not the first, to magnetize iron and steel needles by placing them inside a helix of insulated copper wire connected to the voltaic battery poles. Humphry Davy conducted similar experiments in London at about the same time. The former and the latter, both, found that the needles could also be magnetized by discharging Leyden jars through the wire of the helix.

With Oersted's discovery and the invention of the electromagnet, there could be no more doubt as to the connection between electricity and magnetism. As soon as he heard of Oersted's discovery, Ampere began investigating the nature of the above connection. He was the first to point out the electrical nature of magnetism, i.e., that magnetism was an electrical phenomenon. By his experiments Ampere proved that magnetic effects could be produced without magnets, by means of electricity alone. The space surrounding a current-carrying conductor was a field of magnetic forces, just as was the space surrounding a magnet.

Ampere worked with unbelievable speed and wonderful intuition. He heard of Oersted's discovery on September 11, 1820 and on the 18th of that very month, he presented an account of his experiments as well as their results to the Academy of Sciences.