Although this seems right, that the magnet is being depleted I mean, it
still puzzles me.  When was the last time you heard of someone changing the
magnets in a PM generator? Or, for that matter, in a DC PM motor?  Neither
will work without the magnets, but they don't appear to be consumed in the
process.

I remember as a kid having the 2 "scotty dog" magnets, one black, one white
(N & S polarities.)  You'd put 'em on a tabletop and move one toward the
other.  If they were oriented to attract, at some point they would overcome
the friction of the tabletop and accellerate the stationary one toward the
"attractor."  This obviously requires a not-insignificant amount of energy.
it seems obvious that the energy must be coming from the magnets.  I know it
took energy to make the magnets in the first place, but it is still hard for
me to believe that you could "run down" the magnets by this process any time
soon.

There are no doubt many discoveries waiting to be made in the area of energy
storage and conversion. I have a hunch that some of the most important of
these will result from a whole new understanding of magnetism.

At the risk of burning up the OT bandwidth, I would love to hear the
thoughts of this group on this subject.

        Foster

> -----Original Message-----
> From: pic microcontroller discussion list
> [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Brian Aase
> Sent: Thursday, September 23, 1999 1:29 PM
> To: PICLIST@MITVMA.MIT.EDU
> Subject: Re: [OT] Magnetic Field
>
>
> Oh, Gee.  This design pops up at least once a year and is always
> good for a laugh or two.  :-)
> Most attempts to point out the flaws in it focus on the effectiveness
> of the shield device, and the resulting shape of the flux field.  What
> seems not to get noticed much, is that "permanent" magnets are
> not really permanent at all.  Energy is transferred to the magnet
> material during the magnetization process, and the best one can
> ever do is recover that quantity of energy and no more.
> If someone has figured out how to make a truly non-depletable
> permanent magnet, I'll be the first to invest!
> Brian Aase
>
>
> Wagner Lipnharski wrote:
> >
> > What is the most positive way to block magnetic field using a 5mm *any
> > material* board?
> > Take a look at the picture and tell me why it doesn't work.
> > http://www.ustr.net/jpg/moto1.jpg
>