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Can certain magnets be altered to only attract certain metals and/or other magnets, as opposed to any metal or magnet that happens to be within that magnets range?
It's pretty clear from your question that you are asking about special
types of magnetic fields, not special geometrical shapes or some other
such trick. The answer then is no. There are only a very limited number
of known long-range fields, i.e. fields that extend over perceptible
distances. These are electromagnetism and gravity. The magnetic part of
the electromagnetic force is a simple thing, which does not come in all
sorts of flavors. The magnetic field doesn't bear any traces of what
material it came from.
(published on 10/22/2007)
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