Magnetic fields such as a field from a neodymium magnet?

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Discussion Overview

The discussion revolves around the possibility of blocking or reflecting magnetic fields, specifically those generated by neodymium magnets. Participants explore concepts related to magnetic shielding, materials used for this purpose, and practical applications such as in MRI suites and traffic light systems.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Conceptual clarification
  • Experimental/applied

Main Points Raised

  • Some participants assert that no material can block or reflect magnetic fields, suggesting that magnetic shielding only redirects field lines.
  • Iron is commonly mentioned as a material used for magnetic shielding, but it does not block fields in the conventional sense; it merely concentrates the field where the iron is located.
  • Mu metal is discussed as a potential shielding material, but participants clarify that it also does not block or reflect magnetic fields.
  • One participant describes the effectiveness of shielding materials in MRI suites, where a significant reduction in magnetic field strength is achieved, leading them to consider this as "blocking" the field.
  • Another participant questions the feasibility of achieving low field strengths with mu metal, sharing an alternative method involving substantial amounts of iron for effective shielding.
  • A participant expresses concern about the effects of a strong neodymium magnet on motorcycle circuitry and seeks advice on shielding options, indicating a practical application for the discussion.
  • Some participants suggest that shielding may not be necessary for the specific application of using a neodymium magnet to trigger a traffic light.

Areas of Agreement / Disagreement

Participants generally disagree on the terminology and effectiveness of magnetic shielding, with some asserting that it can be considered "blocking" while others maintain that it merely redirects magnetic fields. The discussion remains unresolved regarding the best materials and methods for achieving effective shielding.

Contextual Notes

Participants reference specific applications, such as MRI shielding and traffic light systems, but the discussion does not resolve the technical details or assumptions regarding the effectiveness of different materials in various contexts.

Chemics
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Is there a material that blocks or reflects magnetic fields such as a field from a neodymium magnet?
 
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No. The best you can do is to move the field lines away from one area and towards another.
 


Right; magnetic shielding is usualy done with iron, which doesn't really "shield" in the conventional sense. Instead, it causes the magnetic field to concetrate where the iron is, thus greatly weakening the field strength beyond that bit of iron.
 


Chemics said:
Is there a material that blocks or reflects magnetic fields such as a field from a neodymium magnet?
Iron or mu metal (sp?)
 


It is spelled "mu metal", but it doesn't block or reflect. All it can do is move field lines from one place to another, like Lurch describes.
 


Chemics said:
Is there a material that blocks or reflects magnetic fields such as a field from a neodymium magnet?
Do you have a specific problem that you wish to apply this to?
 


In the construction of passively shielded MRI suites we call it a shielding material. On one side of the shielding you may have a field of several tesla and on the other side a field of several nanotesla. So to me it seems fair to call that "blocking" the field.

Obviously reflecting is the wrong word, since that refers to a wave behavior. But to me "blocking" seems close enough to "shielding".
 


DaleSpam said:
In the construction of passively shielded MRI suites we call it a shielding material. On one side of the shielding you may have a field of several tesla and on the other side a field of several nanotesla. So to me it seems fair to call that "blocking" the field.

Obviously reflecting is the wrong word, since that refers to a wave behavior. But to me "blocking" seems close enough to "shielding".

Are you saying you've been able to knock an MRI down to nT with mu metal? May I ask how?
 


I have never seen it done with mu metal (too expensive), only iron. But it is pretty simple. Put the MRI in the middle of the room, and then place several hundred tons of iron in the walls ceiling and floor. Outside the room the field is very small.
 
  • #10


I am wanting to use a neodynium magnet to make a traffic light change when i pass over the trigger in the road with my motorcycle but I figured if the magnet is too strong it has to be doing something to the motor or electrical circutry on the motorcycle. So I thought that I would try to shield it somehow using an iron or some kind of material to either block or reflect the magnetic fields. From what people are saying though it sounds like a good reflection or any at all is near impossible or too much work/money.
 
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