Re: jumping ring demo

[paul o johnson <pojhome@FLASH.NET>]

Martha

It's due to Lenz's law which states, "The induced current is always in a
direction opposite to what you calculate."

poj

Martha Takats wrote:

> Would someone point me to an explanation of the jumping ring demo?
> This is the one where you put a nonmagnetic (aluminum) ring over the
> core of an electromagnet and plug the electromagnet into an AC
> outlet. The ring jumps vigorously off. My attempts at analysis
> do not give me a net force in the direction of decreasing field, though
> there clearly is such a force--if you try to hold the ring in place,
> there is a noticeable force trying to make it jump off.
> --
> Martha Takats
> Department of Physics and Astronomy
> Ursinus College
> Collegeville, PA 19426