Approximate and Proper Electromagnetic Modelling in Moving Conductors

A conductor moving in a stationary magnetic field often rises crucial issues at the courses on electromagnetics for electrical engineering students. The correct use of Faraday’s induction law can sometimes be harder than one would think for the first sight. In this paper, we revisit two simple examples of eddy-currents by means of numerical field computation. First, the case of a small magnet falling within a copper tube –which is an impressive experiment as well– is dealt with. Second, a metallic plate moving below a small magnet is examined. In both cases, approximate and proper electromagnetic models are compared. The approximate solutions are usually of satisfying accuracy, but they hide some parts of the physics behind the phenomenon. At the university courses, however, the deep understanding of the electromagnetics must precede the use of practical simplifications, even when using an up-to-date numerical field computation software