[Strange Visitor (OP)]

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!

[RD]

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 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 (e.g. Iron) then they would not block the magnetic field, but would spread it out making it weaker at "O".

[Strange Visitor (OP)]

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?

[lyner]

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

[RD]

The magnetic field generated by 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(]

[Chemistry4me]

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