Method of image charges: any extension for oscillating fields?

AI Thread Summary
The discussion explores the potential extension of the "Method of image charges" to oscillating fields, particularly in the context of radiating problems rather than nearly-static scenarios. The user is interested in applying this method to the near-field of electrostatic antennas while ensuring causality in phase and group velocities. Responses highlight that image currents are relevant in antenna design, especially for whip and monopole antennas utilizing ground planes. However, the complexity of alternating fields introduces challenges, such as the need to account for delays, which complicates the applicability of the image method. The user seeks references to support their pedagogical application of these concepts.
lalbatros
Messages
1,247
Reaction score
2
I was wondering if the "Method of image charges" could be extended even partly or approximately to oscillating charges.

I am not considering nearly-static problems, but really radiating problems.
After all, the Poisson equation and the wave equation are rather close !
Therefore, I thought that maybe in the near-field of an (electrostatic) antenna there could be a way to re-use this good old method.
I must stress however that I want causality to be (reasonnably) ensured, as I am mainly interrested in phase and group velocities results.

Have you seem somthing similar?
Thanks
 
Physics news on Phys.org
Sure, take a look at image currents. Many antennas, i.e. whip and monopole, use a ground plane and image theory in their operation.
 
Born2bwire said:
Sure, take a look at image currents. Many antennas, i.e. whip and monopole, use a ground plane and image theory in their operation.

Born2bwire,

Of course, alternative fields can produce alternating images.
However, this does not imply that this would lead to a useful image method of calculation.
For static fields, the method is obvious and simple, when applicable.
However, for alternating fields, delays have to be taken into account.
For my application (pedagogical), I need to keep a good account of these causal delays.
Would you have some reference for your suggestion?

Tanks!
 
Thread 'Motional EMF in Faraday disc, co-rotating magnet axial mean flux'
So here is the motional EMF formula. Now I understand the standard Faraday paradox that an axis symmetric field source (like a speaker motor ring magnet) has a magnetic field that is frame invariant under rotation around axis of symmetry. The field is static whether you rotate the magnet or not. So far so good. What puzzles me is this , there is a term average magnetic flux or "azimuthal mean" , this term describes the average magnetic field through the area swept by the rotating Faraday...
Back
Top