Re: simple magnets question

[Leigh Palmer <palmer@SFU.CA>]

> We might want to think of it as an electrodynamic coupling.
> There's a ring magnet facing an aluminum disk.
> The magnet rotates.
> The disk follows, restrained by an opposing torque from a hair spring.
> This disk is attached to a pointer. This indicates speed.

Note that the "ring magnet" described above is not magnetized
like Bill's spinning disk; it is more like the spinning
horseshoe magnet someone else described. A similar "ring
magnet" is to be found in a toy called "Top Mystery". The
direction of magnetization is in the plane of the ring; the
gross geometry is misleading. I expect you will find that
your ring magnet is also polarized in a surprising manner.

Leigh