A Simple Demonstration of Back emf

摘要

In discussing motors, one college textbook says,"As the coil (of a motor) rotates in a magneticfield, a back emf is generated that tends to coun-ter the emf that supplies the current." This is a truestatement, but it does little to enhance student under-standing of how and why it is created. In this paper, Iwill explain how to take students step by step throughthe creation of what the experts call "back emf" andthen describe a simple experiment that clearly demon-strates its existence.