Introduction

Building on Unit 3's result that a current-carrying conductor always sets up a magnetic field around itself, physicists in the early nineteenth century naturally began to wonder about the CONVERSE effect: could a magnetic field be made to produce an electric current? A whole series of careful experiments was needed to establish this converse effect rigorously, and this work was carried out by Michael Faraday in the United Kingdom and Joseph Henry in the United States, working almost simultaneously and completely independently of one another. Their efforts succeeded, and the resulting phenomenon -- a changing magnetic field producing an electric current in a circuit -- was named electromagnetic induction. History credits Michael Faraday specifically with the discovery of electromagnetic induction, dated to 1831, because he was the first to publish his experimental results, even though Henry had performed closely related experiments around the same time. The rest of section 4.1 works through Faraday's o …