Regarding magnetic shielding....

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    Magnetic Shielding
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Discussion Overview

The discussion revolves around the concept of magnetic shielding, specifically the use of soft iron and other materials to protect areas from magnetic fields. Participants explore the mechanisms behind magnetic shielding, including ferromagnetism and diamagnetism, and reference various sources for further understanding.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions the effectiveness of soft iron in magnetic shielding, suggesting that induced fields would still affect the area being shielded.
  • Another participant introduces the concept of a Faraday cage as a method of shielding.
  • A participant discusses the properties of soft iron, noting that it does not create permanent magnets and describes the behavior of small magnetic domains and diamagnetism in response to applied magnetic fields.
  • Some participants assert that while the descriptions of diamagnetism and paramagnetism are correct, they challenge the explanation of how magnetic shielding works.
  • There is mention of superconductors and their strong diamagnetic properties, particularly in relation to the Meissner effect, which some find interesting.
  • Participants suggest that the secondary school model of electromagnetic shielding is incomplete but still a good approximation, referencing historical demonstrations by Faraday.
  • There is a call for further investigation into the role of magnetic susceptibility in screening magnetic fields, particularly in relation to soft iron.

Areas of Agreement / Disagreement

Participants express differing views on the effectiveness and explanation of magnetic shielding, with no consensus reached on the adequacy of existing models or the specific mechanisms involved.

Contextual Notes

Some participants note limitations in the secondary school model of electromagnetic shielding and suggest that further exploration of magnetic susceptibility is necessary. The discussion includes references to external sources for clarification, but the applicability of these sources remains a point of contention.

harvey1999
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To protect a place from magnetic fields, soft iron is placed around the place, right?
so when magnetic field passes through the soft iron, the soft iron becomes an induced magnet, thereby creating induced fields, which makes no sense as the induced fields would still hit the place. please explain in simple terms? thank you.
 
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Google: faraday cage.
 
I've read about different types of iron just a little and it appears some forms of iron, particularly soft iron do not make permanent magnets, but instead have small domains everywhere where inside the iron there are millions of small permanent magnets whose magnetic fields point in every direction and thereby pretty much cancel. Meanwhile, there is another effect (besides ferromagnetism), called diamagnetism, where the free (conduction) electrons in the iron will partially shield any magnetic field, because the free electrons will respond to an applied magnetic field in such a way (.g. making circular orbits) as to generate magnetic fields of their own that oppose the applied magnetic field. In diamagnetism (as opposed to ferromagnetism), the response is opposite that of the applied field. I can't claim to be an authority on this subject, but I do think this is accurate.
 
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Have a look at the links please.
 
Simon Bridge said:
Have a look at the links please.
Thank you. The screening mentioned in the "links" by the superconductors is particularly interesting. The diamagnetism exhibited by these (i.e. which results in the Meissner effect), is apparently very much stronger than that of ordinary (conductor) materials with free electrons. Additional comment is a system of free electrons, like those found in a conductor, would be expected, by Le Chatlier's principle, to respond in such a manner as to reduce the effect of the applied magnetic field.
 
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If anyone thinks the secondary school model for how conductors can screen out EM is incomplete, they are correct.
However, it is a very good approximation that was demonstrated by Faraday and many others since.
The role of magnetic susceptability in screening magnetic fields should be investigated by the student also - this will be behind the mention of soft iron in post #1 - but, hopefully, the links will have answered the concerns Harvey1999 originally had.
 
Simon Bridge said:
If anyone thinks the secondary school model for how conductors can screen out EM is incomplete, they are correct.
However, it is a very good approximation that was demonstrated by Faraday and many others since.
The role of magnetic susceptability in screening magnetic fields should be investigated by the student also - this will be behind the mention of soft iron in post #1 - but, hopefully, the links will have answered the concerns Harvey1999 originally had.
thank you
 
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