THE ORIGIN OF THE DYNAMO
The very first studies that had to do with the mutual relations of electricity and magnetism were made by Hans Christian Oersted, the Dane, as early as 1815. He discovered that a magnetic needle is influenced by the passage near it of a current of electricity, demonstrating, therefore, that the electric current in some way invades the medium surrounding any conductor along which it is passing. Oersted's experiments were repeated, and some new phenomena observed by the Frenchman André Marie Ampère and Dominique François Arago. Arago constructed an interesting device, in which a metal disk was made to revolve in the presence of a current of electricity; but neither he nor anyone else at the time was able to explain the phenomenon.
In 1824 an advance was made through the construction of the first electric magnet by Sturgeon. Hitherto it had not been known that a magnet could be made artificially, except by contact with a previously existing magnet. Sturgeon showed that any core of iron may be rendered magnetic if wound with a conducting wire, through which a current of electricity is passed. The experiments thus inaugurated were followed up in America by Joseph Henry of Albany who made enormous electromagnets, capable of sustaining great weights. One of his magnets, operated by a single cell, was able to lift six hundred and fifty pounds of metal.
It was this apparatus which was subsequently to make possible the utilization of electricity as a working force, but as yet no one suspected its possibilities in this direction.
It remained for Michael Faraday, in 1831, to make the final experiment which laid the secure foundation for the new science of electrodynamics. Faraday constructed a tiny apparatus, consisting of a magnet between the poles of which a metal disk was placed in such a way that it could revolve on an axis, the disk being connected with a wire conveying an electric current.
The details as to this most ingenious mechanism need not be given here. Suffice it that Faraday demonstrated the interrelations of magnetism and electricity and the possibility of causing a metal disk to revolve through this mutual interaction. In so doing he constructed the first dynamo-electric machine. In his hands it was a mere laboratory toy, but the principles involved were fully elaborated by the original experimenter, and stated in precise language which modern investigators have not been able to improve upon.
Several decades elapsed after Faraday's initial experiment before the phenomena of magneto-electricity were proved to have any considerable commercial significance. A vast amount of ingenuity was required to devise a mechanism which could advantageously utilize the principle in question for commercial purposes. Indeed the early experimenters did not at once get upon the right track, as their efforts were influenced disadvantageously by an attempt to follow the principle of the steam engine. Some interesting mechanisms were devised whereby the motion of an armature in being drawn toward an electromagnet could be translated into rotary motion through the use of crank-shafts and even of beams, precisely comparable to those employed in the steam engine. Such devices worked with a comparatively low degree of efficiency and were totally abandoned so soon as the idea of getting rotary motion directly from the magnet or armature was made feasible. The names of Saxton, Clarke, Woolrich, Wheatstone, and Werner Siemens are intimately connected with the early efforts at utilization of magneto-electric power. The shuttle-wound armature of Siemens, invented in 1854, marked an important progressive step.