Why are the electric and magnetic fields in an electromagnetic wave propagating through a conductor not in phase?

被引:0
|
作者
Milsom, John A. [1 ]
机构
[1] Univ Arizona, Dept Phys, 1118 E 4th St, Tucson, AZ 85721 USA
关键词
electromagnetic waves; conductors; phase delays; physics education;
D O I
10.1088/1361-6404/aceadf
中图分类号
G40 [教育学];
学科分类号
040101 ; 120403 ;
摘要
Intermediate and advanced texts in electromagnetic theory frequently discuss infinite plane waves propagating through conducting media. They find that the magnetic field has a phase delay (relative to the electric field) that can be as large as pi/4 rad depending upon the ratio of the conductivity to the product of the angular frequency and the permittivity [sigma/(omega epsilon)]. The expressions given to calculate this phase delay are unnecessarily complicated and provide minimal physical insight. We provide a simple expression for the phase delay and then illustrate how to interpret it by first considering Ampere's Law and Faraday's Law separately and then coupling them together. In the classroom, this provides an excellent educational opportunity for our students since we make analogies between the phase shifts associated with Ampere's Law and equivalent phase shifts in driven oscillators and alternating current RC circuits.
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