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Re: Magnetic pendula



A sense coil may be arranged to trigger an electromagnet off-center.

Brian W.

At 10:52 AM 5/19/2004, you wrote:
We have all seen those desktop novelties: battery powered pendula, a
metallic circular frame rotating within a swinging circular frame. Some
look (kind of)like bohr atoms, some have a model space shuttles going around
in apparently chaotic behavior.

A battery powers an electromagnet in the base, which acts on a permanent
magnet embedded in the pendulum. Somehow this keeps the pendulum going
despite frictional losses.

Thinking about it has me wondering why the force from the electromagnet
doesn't do as much slowing down of the pendulum as it does speeding up.
Any ideas?

Richard Zajac


Brian Whatcott Altus OK Eureka!