This green magnetic viewing film will become lighter
or darker when a magnetic field is applied. It turns dark when the
field lines are perpendicular the the surface, and it turns light when
the field lines are horizontal, i.e., across the surface. If a magnet
is placed under it, with one of the poles facing the film, it will show
the magnet as dark with a light outline. The effect gets interesting when
you have lots of magnets, or magnets that are polarized in a unique way.
The entertainment value of this stuff is unmatched, even by the likes of
playing Pac-man or watching professional wrestling!
Here is the view of the fields of a surplus hard drive magnet. This clearly demonstrates how the magnet is polarized
with both a north and south pole on each flat face of the magnet.
Now we start to have fun with stacks of magnets!
Here we have a stack of small ring magnets with the film placed directly on the poles.
The same magnets with the film on the sides.
Here is the film on the sides of long rod magnets. Remember that these are polarized along the long edge of the magnets.
Rod magnets with film at the ends.
Small cube magnets shown at the poles.
The same small cubes shown along the sides of the magnets.
Although they will attract and stick together along the sides, this clearly
demonstrates why the attraction is so much stronger at the poles.
A view of the poles of some rectangular block magnets. These ones are clearly polarized along the long narrow edges.
The flat surfaces through which the magnets are polarized.
And along the short narrow edges of the same.
And now for something completely different....Spheres!
Here shows what was a surprise to me...the film over a
block of 1/4 inch sphere magnets.
A pile of 3/4 inch sphere magnets.
Even the most basic rubberized refrigerator magnets can
be interesting. As you can see here, poles alternate in strips across the
face of a fridge magnet. The field is weak on these, and with a neodymium
magnet, you can easily de-magnetize them, and change the orientation of
Here we applied a fridge magnet to a large neodymium magnet
to "erase" it; then we placed a magnet on it briefly, and you can see
that the refrigerator magnet retains a shadow of the neo magnet which is
no longer there. The fridge magnet clearly has some magnetization, but
much less than it used to. It will barely hold itself to the fridge, but
can no longer hold a sheet of paper up.