The Magnetic Fields Produced by Electric Currents

Abstract

The fact that an electric current always produces a magnetic field, no matter what the shape of the circuit may be, was discovered accidentally by Oersted in 1820. He was demonstrating what he believed to be the non-connection between electricity and magnetism. On arranging a current-carrying wire parallel to a compass needle he was surprised to find that the needle was deflected. On reversing the current the defection was reversed.