At the Exploratorium, we have put together an exhibit that has two parallel
columns of strong, not rare earth, permanent magnets. They are
approximately 4 inches x 8 inches x 1 inch (10 cm x 20 cm x 2.5 cm). We
drop an aluminum disk between the two sides.
We've arranged them with all the poles on one side
N S
N S
N S
N S
N S
N S
N S
N S
And we have also arranged the magnets with alternating poles like this
N S
N S
S N
S N
N S
N S
S N
S N
The disk falls slower (has a lower terminal velocity) in the alternating
version.
I'm not sure why. If it isn't my imagination, do you think having it
alternate more often would make the disk fall even slower?
Finally, when a cylindrical magnet falls down a tube near the same
diameter, the magnet seems to stay centered in the tube. I'm not sure why.
Maybe it isn't so much electromagnetic fields but aerodynamics?
In any case, the disk hugs one side while falling, rubbing against the
magnet. Is there a way to get the disk to fall more centered between the
two columns of magnets?
Thank you in advance,
Zeke
--
*Marc "Zeke" Kossover | Educator, Teacher Institute*
zkossover@exploratorium.edu
Museum: Pier 15, San Francisco, CA 94111
Mailing: 17 Pier, Suite 100, San Francisco, CA 94111