Radiation vector for a short dipole near a perfect magnetic conductor

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Discussion Overview

The discussion revolves around the calculation of the radiation vector produced by a short dipole near a perfect magnetic conductor, specifically in the context of applying the images method. Participants explore the implications of using a perfect magnetic conductor compared to a perfect electric conductor.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant proposes using the images method to calculate the radiation vector for a short dipole above a perfect magnetic conductor, questioning how this differs from the case with a perfect electric conductor.
  • Another participant defines the characteristics of perfect electric and perfect magnetic conductors, highlighting the boundary conditions for electric and magnetic fields.
  • A different participant mentions that at very low frequencies, materials like mumetal and permalloy can act as good magnetic conductors, suggesting that the image current would need to be opposite to achieve zero magnetic field at the magnetic conductor.
  • One participant expresses confusion, questioning whether the radiation vector would be zero due to the opposite currents in the image dipoles.

Areas of Agreement / Disagreement

Participants express differing views on the implications of using a perfect magnetic conductor, particularly regarding the behavior of the radiation vector and the nature of image currents. The discussion remains unresolved with multiple competing perspectives.

Contextual Notes

There are limitations regarding the assumptions made about the behavior of currents and fields at the boundaries of perfect magnetic conductors, as well as the specific conditions under which these materials operate effectively.

Bromio
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Hi there.

If I wanted to calculate the radiation vector (in z > 0) produced by a short dipole with uniform current Io (+z direction) on a infinite perfect electric conductor (plane z=0), I'd have to apply the images method. So I'd have to calculate the radiation vector produced by two short dipoles, one in z > 0 and one in z < 0, with currents Io.

However, if we change the perfect electric conductor by a perfect magnetic conductor, how can I apply the images method?

Thank you.
 
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Bromio said:
Hi there.

If I wanted to calculate the radiation vector (in z > 0) produced by a short dipole with uniform current Io (+z direction) on a infinite perfect electric conductor (plane z=0), I'd have to apply the images method. So I'd have to calculate the radiation vector produced by two short dipoles, one in z > 0 and one in z < 0, with currents Io.

However, if we change the perfect electric conductor by a perfect magnetic conductor, how can I apply the images method?

Thank you.

What's a perfect magnetic conductor?
 
It's an idealization.

PEC (Perfect Electric Conductor): \hat{n}\times\vec{E}=0 and \hat{n}\times\vec{H}=\vec{J}_s.

PMC (Perfect Magnetic Conductor): \hat{n}\times\vec{E}=-\vec{M}_s and \hat{n}\times\vec{H}=0.

Thank you.
 
At very low frequency, mumetal of permalloy are good magnetic conductors.

It would change the sign of the current in the image. Opposite current achieve zero magnetic field at the magnetic conductor, while same currents achieve zero electric field.
 
Hi.

I understand what you say, but, in that case, radiation vector is 0 (because currents are opposite), isn't it?

Thank you.
 

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