The search for electromagnetic induction, 1820-1831

Oersted´s discovery in 1820 of the magnetic field that surrounds a conductor during the passage of an electric current, aroused a wave of interest among men of science in England, France, Germany, Italy, and the United States. The apparatus required to verify his results was easily put together, and anyone who cared to do so could see for himself the nature of the indissoluble connexion between electricity and magnetism, which, though long suspected and vaguely adumbrated, was now precisely defined and made a permanent portion of the corpus of science. As one subsequent discovery after another was announced from various places, the recognition became widespread that a large and unexploited field for investigations and applications had been opened up. Only one week after word of Oersted’s experiment reached Paris, Ampere discovered that two parallel wires that carry parallel currents attract each other. Less than two months after Oersted’s publication, J. S. C. Schweigger (1779-1857), at the University of Halle, reasoned that if the current in a single wire held above the compass needle would deflect the needle to the right, while the same wire placed beneath the needle would deflect it to the left, one turn of wire, placed around the needle in the plane of the magnetic meridian, would exert twice the deflecting force of a single wire; and a coil made of ten turns of insulated wire would exert twenty times the force.