Electromagnetic Induction

Section 4.1, Electromagnetic Induction, opens the unit by asking the converse of what Unit 3 (Magnetism and Magnetic Effects of Electric Current) established. Unit 3 showed that an electric current always produces a magnetic field around it -- discovered by Christian Oersted and extended by Ampere, who proved that a current-carrying loop behaves exactly like a bar magnet. This section instead asks: can a magnetic field, in turn, be used to PRODUCE an electric current? Answering this question rigorously -- through a careful series of experiments performed independently by Michael Faraday in the UK and Joseph Henry in the USA around 1831 -- is the achievement that gives this section, and the whole broader phenomenon, its name: electromagnetic induction. The section works through the concept of magnetic flux (4.1.2), Faraday's own experiments and the two laws he drew from them (4.1.3), Lenz's law for finding …