MadSci Network: Physics |
If you try to "build" a magnetic monopole by arranging a sphere of magnets so that all the north poles are pointing outside and the south poles are pointing inside, all the magnetic fields will cancel -- both inside and outside.
But just because the magnetic fields go away doesn't mean that the material changes. The magnets continue to have the same properties, it's just that the fields of some magnets are cancelled by the fields of other magnets. (Also, I'm pretty sure that it would fall apart if nothing was holding it together.)
If one piece is missing from the sphere, then the magnetic field lines can connect through the hole, which would make the magnetic field near the hole very strong, as you suggest.
As for your last question, if the sphere is perfect, the magnetic field goes away entirely. It's not hiding anywhere -- it's just not there.
Here is a good page about magnetic fields, including pictures that will help you visualize field lines from various objects.
Of course, it's possible that one day someone will find a new particle that has a magnetic charge, and then you'd have a natural magnetic monopole!
Try the links in the MadSci Library for more information on Physics.