Permanent Magnets: Electromagnetic Wave Propagation?

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Discussion Overview

The discussion centers on the relationship between permanent magnets and electromagnetic wave propagation, specifically whether a permanent magnet generates electromagnetic waves and the conditions under which such waves might occur. The conversation includes theoretical considerations and practical implications related to magnetic shielding.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Mike questions whether a permanent magnet is associated with electromagnetic wave propagation and asks about the frequency of such waves.
  • One participant states that under current knowledge, the frequency of waves associated with a permanent magnet is zero, as the magnetic field does not alternate.
  • Warren explains that the magnetic field is static (magnetostatic) unless the magnet is moved, in which case the field oscillates at the frequency of the movement.
  • Another participant elaborates that a "wave" occurs only when the magnetic field changes, leading to the generation of electromagnetic waves, which does not happen with a static field from a permanent magnet.
  • Michael raises a question about the use of magnetic shields with permanent magnets, noting a discrepancy between literature and online sources regarding the shielding of magnetostatic fields and his own simulation results showing shielding by nickel.

Areas of Agreement / Disagreement

Participants express differing views on the nature of electromagnetic wave propagation related to permanent magnets, with some asserting that no waves are produced by static fields while others discuss conditions under which fields can change. The discussion regarding magnetic shielding also reveals conflicting perspectives on its applicability to permanent magnets.

Contextual Notes

There are unresolved assumptions regarding the definitions of wave propagation and the conditions under which magnetic shielding is effective. The discussion does not clarify the specific parameters that might influence the behavior of magnetic fields in different contexts.

miloko
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Hi all,
I have this simple question that I never really understood. A permanent magnet generates a magnetic field around itself. Is there an electromagnetic wave propagation associated with this permanent magnet? If so, what is the frequency of the wave?

Thanks,
Mike
 
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Under current knowledge, the frequency is zero(it does not alternate with a permanent magnet) but the propagation of the magnetic field is at the speed of light.
 
The field is static and unchanging (magnetostatic) if the magnet is not moved. If you begin shaking it, then the field undergoes an oscillation with the frequency of the shaking.

- Warren
 
In other words, a "wave" occurs when the field changes. A regular change in a magnetic field causes a regularly changing electric field which produces a regularly changing magnetic field which produces ... (that's why the waves are called electromagnetic waves). With a permanent magnet, there is no changing field and so no wave.
 


Hi all,

In one of the books I'm reading, it says that shields are only used in the presence of alternating fields. However, in some websites, I see people using magnetic shields for permanent magnets which has a magnetostatic field. I ran some simulations, and the filed of a permanent magnet seems to be shielded by a layer of nickel. So, who's telling the truth?

Thanks,
Michael
 

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