Naked Science Forum

General Science => General Science => Topic started by: Strange Visitor on 21/02/2009 08:01:40

Title: Is it possible for magnetism to reach through several layers of metal?
Post by: Strange Visitor on 21/02/2009 08:01:40

How far can a magnet or electromagnetic extend its field?  Will thin layers of metal block magnetism from reaching through?

Picture three layers of thin metal like this, with about 2 inches of space between each layer:
O| | |M

Where O is a small metal object and M is the magnet.  If the three layers don't move, is there any way for some magnet to still pull the object back firmly against the far layer?

I'm wondering about the "dangerously powerful" magnets from places like United Nuclear, if even as strong as they are, their force will only affect an object within about an inch or two of them.  Are there any magnets strong enough to do what I described?

Thanks!

Title: Is it possible for magnetism to reach through several layers of metal?
Post by: RD on 21/02/2009 14:15:53

Quote from: Strange Visitor on 21/02/2009 08:01:40

Picture three layers of thin metal like this, with about 2 inches of space between each layer:
O| | |M

Where O is a small metal object and M is the magnet.

If the three layers don't move, is there any way for some magnet to still pull the object back firmly against the far layer?

If the layers of metal are Aluminium (http://en.wikipedia.org/wiki/Permeability_(electromagnetism)#Values_for_some_common_materials) and the small metal object is a Iron, the object will still be strongly attracted to the magnet.

If the layers of metal are ferromagnetic (http://en.wikipedia.org/wiki/Ferromagnetic) (e.g. Iron) then they would not block the magnetic field, but would spread it out making it weaker at "O".

Title: Is it possible for magnetism to reach through several layers of metal?
Post by: Strange Visitor on 22/02/2009 00:07:26

Thanks RD!  Are there any magnets that have a field strong enough to attract, say, a 1 inch iron ball bearing from 6 inches away?

Title: Is it possible for magnetism to reach through several layers of metal?
Post by: lyner on 22/02/2009 00:57:05

There are loads of modern magnet materials which could do that. The miniature motors in toys and electronic gizmos have incredibly strong magnets in them. Or did you mean "lift"? That might be harder to do.
btw ball bearings are steel

Title: Is it possible for magnetism to reach through several layers of metal?
Post by: RD on 22/02/2009 02:02:54

The magnetic field generated by MRI (http://en.wikipedia.org/wiki/MRI) scanners is enormous: evidently sufficiently strong to lift a floor polisher ...


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http://mrimetaldetector.com/blog/?p=19

A good job no-one was being scanned at the time  [xx(]

Title: Is it possible for magnetism to reach through several layers of metal?
Post by: Chemistry4me on 22/02/2009 02:08:03

Eeek, I wouldn't want to be caught in between those two things!