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