关键词: 导电介质, 金属导体, 复介电常数, 电磁波传播

Abstract: In the discussion of electromagnetic（ EM） wave propagating in conductors,a majority of Chinese electrodynamics textbooks start from EM wave propagation in an insulating dielectric,and then describe EM wave propagation in conductors upon the introduction of a complex permittivity. Such a treatment makes the form of EMwave equation for a conductor fully consistent with that for an insulating medium. But a lot of textbooks do not provide an analysis of the physical meaning of the complex permittivity before the relevant discussions. This could easily lead to confusions for students who could suppose incorrectly that the complex permittivity introduced here for a conducting dielectric medium is exactly the dielectric constant of metals for EM waves. Secondly,most of the textbooks do not distinguish different underlying mechanisms that lead to high-reflective characteristics for EM waves incident either on the surface of a conductor with a good conductivity or on a metallic conductor. In this article,the author discusses the concept of complex permittivity,followed with the analysis on several issues that adopt this concept and finally make some suggestions for peer reference in their teaching.

Key words: conducting dielectric medium, metallic conductor, complex permittivity, EM wave propagation