But nobody answered my question. FWIW, I guess that pendulum 2 will
have the shorter period because there's less Al for the eddy currents
to swirl around in, or to put it another way the Hall effect will
limit the flow of free charges. In fact if it wasn't for the fact
that the bob's velocity is variable (if instead it were to go all the
way around by turning my apparatus horizontally), after an initial
deceleration, the 2nd bob would move at constant speed ignoring axle
friction & air drag (in contrast to the 1st bob which would
magnetically slow to a stop). Right?
1. A cylindrical magnet is a pendulum bob on a toothpick arm swinging
entirely between two parallel Al plates. The two flat faces of the
magnet are its poles and they are parallel to the plates.
2. A cylindrical Al bob on the same arm swinging entirely within two
poles of a large C-shaped magnet. For simplicity, assume the pivot of
the toothpick is at the center of a pole face, so the bob always sees
the same strength magnetic field as it swings. That strength is the
same as that of the magnet bob in case 1. Size of bob and plates are
about the same in both cases.
Which pendulum will have a shorter period and why? -Carl
--
Carl E Mungan, Assoc Prof of Physics 410-293-6680 (O) -3729 (F)
Naval Academy Stop 9c, 572C Holloway Rd, Annapolis MD 21402-1363 mailto:mungan@usna.eduhttp://usna.edu/Users/physics/mungan/