Fields that are always dynamic (electromagnetism)

摘要

An approach to undergraduate electromagnetics is outlined that differs from the traditional sequence of statics followed by electrodynamics. The purpose is to capture student interest while teaching relatively simple fields by relating the topics to electric, magnetic, and electromagnetic device examples. This is done by addressing electrostatics and magnetostatics as quasistatics, so that the fields are always dynamic. A side benefit is that electro and magneto-quasistatic (EQS and MQS) fields can be more easily realized and measured than static fields, allowing for a wealth of lecture demonstrations, some of which are described. The interaction of fields with matter is emphasized, with examples taken from electrostatic precipitators, the current and charges induced in a person by a power line, magnetic recording, magnetic (i.e. electric) motors, antenna, etc. The introduction of magnetization parallels that of polarization, using the Chu formulation of electrodynamics.