Magnetic Forces

Abstract

The age of electromagnetism was launched in 1819, when Hans Christian Oersted noticed, during one of his lecture demonstrations, that an electric current deflects a magnetized needle: magnetism is a manifestation of electricity. After a few months of intense international experimentation, it became clear that (1) steady electric currents produce steady magnetic forces, and (2) these forces are felt by the currents themselves. Most implications, including some of the deeper theoretical ones, were already worked out by 1825, largely through the investigations of Ampère.