Chapter 16: Induced Currents – Motors & Generators

Induced Currents – Motors & Generators physics chapter explores the foundational concepts of electromagnetic induction, beginning with the historical discovery in the 1830s that linked electricity and magnetism, culminating in Michael Faraday's crucial finding that current is induced in a conductor only when the magnetic flux passing through the circuit is changing. The mechanism involves a magnetic field exerting a sideways force on the electrons within the conductor, creating an integrated force known as the electromotive force, or emf. Faraday demonstrated that this emf can be induced in three primary ways: moving a wire relative to a magnetic field, moving a magnet relative to a wire, or varying the current in a nearby circuit. This foundational principle underlies the function of crucial electrical technology, including generators, which convert mechanical motion into electrical energy, and motors, which perform the reverse operation; the two are shown to be reciprocal devices. The chapter details self-inductance, where a changing current in a single coil induces an emf in itself, often described as a form of electrical inertia that opposes rapid current changes. A central theme is Lenz's Rule, which dictates that the direction of the induced current is always such that its own magnetic field opposes the change in the original magnetic flux that produced it, dramatically demonstrated by the repulsion of a conducting ring when the magnetic field is rapidly changed. Furthermore, the text introduces eddy currents—induced currents occurring within bulk conductors—which are responsible for phenomena like magnetic damping in mechanisms such as the copper pendulum. Finally, these principles are applied to describe transformers, which efficiently use a varying magnetic field to transfer energy between two separate coils, and the practical function of the induction motor, which operates using a rotating magnetic field to exert torque on a conducting rotor, underscoring how Faraday’s pioneering discoveries initiated modern electrical technology and engineering.