Non-diy_efi, dyno help

[David Cooley]

At 12:09 PM 6/18/99 -0400, you wrote:
>
> Yes but eddy currents are not magnetic, they are electric.
> Have you ever wondered why transformer cores are made of little plates
>rather then a solid chunk of iron?? Read on Mc Duff
>
>> 

Yes, but the two are inter-related...   Changing magnetic fields induce
electrical eddy currents in metals, and those eddy currents generate
magnetic fields that oppose the fields that cause the electrical eddy currents.

I used to demonstrate this when I worked on MRI systems...  I'd take an
Aluminum sign, 3/32" thick (not critical as to composition, just any
non-magnetic metal works) and stand it up on edge in the bore of the MRI
magnet (1 Tesla or 1.5 Tesla Superconducting magnet). and give it a tap to
knock it over... It would take between 15 and 30 seconds to fall depending
on which one of the 2 magnets it was in...
You can also hold it and wave it like a fan in the bore of the magnet and
it feels like it's under water and actually flexes and bends as you move it
through the field due to the eddy current induced magnetic field in the
plate (sign) that opposes the main MRI magnet's field.
Later,
Dave

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