Introduction conduction process represent macroscopic models for the migration of charges in materials under the influence of an electric field. Ideally, quasi-static magnetic field systems are characterized by perfectly conducting (a --* oo) current loops, in which case static conditions (a/at = 0) result in zero electric field intensity. All practical conductors (except super-conductors) have finite conductivity; consequently, a system is modeled as a magnetic field system when the electrical conductivity a for a current loop is high enough to cause only small departures from the ideal. Thus in Chapter 2 iron structures with coils of wire wound around them are represented as ideal (electrically lossless) magnetic field systems in which the winding resistance is included as an external resistance in series with the winding terminals. 1.1.16 Electric Field Systems The electromagnetic field and source quantities in an electric field system are related by the following partial differential equations: V x E = 0, (1.1.11)
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Magnetic Field, Electric charge, Electric Field Systems