Chapter 12 - Faraday's Law of Electromagnetic Induction

Abstract

This chapter describes the faraday's law of electromagnetic induction and its application to circuits. Electromagnetic induction can occur in an electric circuit C in many ways. Some of Faraday's original experiments introduce the useful terminology of primary and secondary circuit. The primary circuit is the source of the time-varying magnetic flux, usually due to electric current driven by a battery. The secondary circuit is the circuit to which Faraday's law is applied, and in which the electromagnetic force (EMF) is induced, as determined by the deflection of a galvanometer or some other measuring device. Faraday gave a rule for the direction of the circulation of the induced electric current circulating around an electric circuit. Another rule for the direction of induced currents was given by Lenz in 1834. Translating it into modern terminology, Lenz's is the most complete and accurate qualitative statement of Faraday's law. It is formulated in terms of the idea of magnetic flux. For Gauss's law, the electric flux through a closed surface is what mattered. For Lenz's law, what counts is the magnetic flux through an open surface, defined by the circuit whose induced electromotive force (emf) one seeks. One way of visualizing a change in magnetic flux through a circuit is to think, as did Faraday, in terms of field lines crossing the electric circuit.