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Posted by Carl McIver on August 24, 2007, 12:41 pm
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Eddy currents. A magnetic field moving through a conductor sets up
electric currents around the flux lines. These electric currents set up a
resultant magnetic field, which just happens to oppose the magnetic field
which created it all to start with. It's sort of perpetuates itself,
falling off based on the losses (electrical resistance) in the materials.
Drop a magnet down a sheet of aluminum, copper, and non-ferrous
non-conducting materials. Copper and aluminum will slow the magnet's
falling down.
You can find out a lot more on the web, and some interesting videos on
youtube and the like.
> --I was welding a little tab onto one side of a length of 1" square
> tubing the other day and suddenly it started to wobble; fairly high rate,
> maybe 10 cycles per second. The tube wasn't fixed to the table, but was
> sitting on a couple of pieces of 2" square tubing that was on the table.
> I removed magnets from the vicinity and tried again; same thing! Could
> this
> something to do with settings on my inverter? Weird!
>
> --
> "Steamboat Ed" Haas : A steaming pile of
> Hacking the Trailing Edge! : obscure information...
> www.nmpproducts.com
> ---Decks a-wash in a sea of words---
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> tubing the other day and suddenly it started to wobble; fairly high rate,
> maybe 10 cycles per second. The tube wasn't fixed to the table, but was
> sitting on a couple of pieces of 2" square tubing that was on the table.
> I removed magnets from the vicinity and tried again; same thing! Could
> this
> something to do with settings on my inverter? Weird!
>
> --
> "Steamboat Ed" Haas : A steaming pile of
> Hacking the Trailing Edge! : obscure information...
> www.nmpproducts.com
> ---Decks a-wash in a sea of words---