How do I contain a magnet's magnetic field?

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SUMMARY

This discussion focuses on safely containing the magnetic field of Neodymium Iron Boron (N45) magnets. The key takeaway is that while the strength of a magnet decreases with distance, using a medium-sized box can help maintain a safe distance from metallic objects. Soft iron is identified as the most effective material for blocking magnetic fields, as it redirects the magnetic field lines. The discussion also clarifies that the decay of magnetic field strength follows an inverse square law, not a cubic relationship.

PREREQUISITES
  • Understanding of Neodymium Iron Boron magnets and their properties
  • Basic knowledge of magnetic field behavior and distance effects
  • Familiarity with materials that influence magnetic fields, particularly soft iron
  • Awareness of postal regulations regarding shipping strong magnets
NEXT STEPS
  • Research the properties and applications of Neodymium Iron Boron magnets
  • Learn about the inverse square law in magnetism and its implications
  • Investigate the use of soft iron for shielding magnetic fields
  • Explore safe storage solutions for strong magnets, including box designs
USEFUL FOR

This discussion is beneficial for hobbyists, experimenters, and educators working with strong magnets, as well as safety professionals concerned with handling and storing magnetic materials.

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I want to buy a Neodymium Iron Boron magnet (N45 or higher), the ones with a very strong pull force. I want to keep it somewhere safe when I'm not doing experiments with it. Is there a way to contain the force so my metals don't fly half way across the room smacking my face along the way? Maybe a box I can put it in? Thanks.
 
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OK, they're not exactly that strong. :rolleyes: The strength of a magnet drops off as the cube of the distance. You don't need to block the magnet so much as you just need some distance. If the magnet has several inches separating it from anything coming close (say, by putting it in a medium-sized box) nothing will be unduly attracted to it.

But that being said, the one thing that best "blocks" magnetism is soft iron. The magnetic field will tend to follow the iron rather than passing through it. However, your implementation is a bit usual - usually you're trying to keep magnetism from affecting something inside a box. i.e. the magnetic field will go around the outside of the box rather than thorugh it.
 
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Just reading through. Just noticed one thing that bothered me. Magnetism is an inverse square law, so it wouldn't be the "cube" of the distance. moving two meters away would mean 1/4 of the original field strength.
 
theantivirus said:
Just reading through. Just noticed one thing that bothered me. Magnetism is an inverse square law, so it wouldn't be the "cube" of the distance. moving two meters away would mean 1/4 of the original field strength.
Can you please supply a citation for this? I think it's the cube but I'm willing to be corrected.
 
A monopole field will scale as inverse square. So how will the long range field of two monopoles (= 1 dipole) scale?
 
I am sorry. It appears as though I was thinking about the magnetic monopole, wherever that may exist. The magnetic field strength decay has an inverse cube proportionality. Excuse me for the mistake.
 
I don't remember the web-site where I purchased 8 large NIB magnets, but I do remember how they shipped them.

When I opened the cardboard box, there were 2 U-shaped/square soft iron "shields' that I had to remove(easily), and the NIB's were inside embedded in some type of styrofoam mold.
I'm sure part of this was due to some postal regulation, but I was impressed.
 

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