Now we shall turn to Faraday's electrical discoveries and inventions. Men had long known that, in houses that have been struck by lightning, steel objects such as knives and needles are sometimes found to be magnetized. Ships struck by lightning had found their compass-needles pointing south instead of north, or wandering in direction and worthless. Men had wondered how an electrical discharge could magnetize steel. They had tried the spark of the electrical machine with no definite result. Franklin, in his experiment of magnetizing a steel needle by passing an electric spark through it, could not tell before the spark was passed through the needle which end would be the north pole. There was no seeming connection between the direction of the electric discharge and the polarity of the needle. After the discovery of the electric battery, men tried to discover a relation between the electric current and magnetism.
Oersted and Electromagnetism
The first success in this direction was achieved by Hans Christian Oersted, a native of Denmark. Poverty impelled his father to take him from school at the age of twelve and place him in an apothecary's shop. The boy, Hans, found delight in the chemical work of the apothecary. His eagerness to learn and the pressure of poverty led him to neglect the usual sports of boyhood and devote his leisure time to reading and study. Again he entered school, and, though paying his way by his own work, he graduated with honor from the University of Copenhagen. He was appointed Professor of Physics in this university, and here he made his first great discovery in electromagnetism.
After working for seven years to discover a relation between current electricity and magnetism, he made a discovery which proved to be the first step in the invention of the dynamo. He was using a magnetic compass, which is a small magnetic needle balanced on a steel point. The needle points nearly north and south unless disturbed by a magnet brought near it. He had tried to find if a wire through which a current is flowing would disturb the compass as a magnet does. He had tried placing the wire east and west, thinking the compass-needle would follow the wire as it does a magnet. One day, while lecturing to his students, it occurred to him for the first time to place the wire north and south over the compass-needle. He was surprised and perplexed as he did so to see the needle swing round and point nearly east and west (Fig. 21). On reversing the current the needle swung in the opposite direction. He had discovered the magnetic action of an electric current. It was learned soon afterward that a coil of wire with an electric current flowing through it acts like a magnet, and that a current flowing around a bar of soft iron makes the iron a magnet (Figs. 22 and 23).
FIG. 21–OERSTED'S EXPERIMENT
An electric current flowing over the compass-needle toward the north causes the needle to turn until it points nearly west.
By permission of Joseph G. Branch.