Joseph Meehan wrote:

FiNOH wrote:

A 9 yr old had a question I couldn't answer. Where do magnets get
their power? Why doesn't it run out?


Thanks
FINOH #29718
Finoh #28437
FiNOH #27447
I love spacefed.


They get their "power" from different things. In the case of natural
magnets they get their power from the spinning of the earth.

Power is not a good term to use, because it is likely to be confused
with energy. Their power is a magnetic alignment that creates a static
field when may well extend well beyond the magnet. When the field is
static, no energy is used.

Moving the field takes energy and the movement of the filed creates an
opposing energy. That is why moving a wire through a magnetic field will
move electrons (electricity) in the wire.

OK guys, that is overly simplified, but that is the idea.




Just last week I learned a neat simple demo you can do with high energy
magnets.

I used a 1/2" diameter by 1/2" long magnet, but it could as well have
been two or three thinner 1/2" diameter magnets stuck together.

When dropped into an upright foot long length of 1/2" copper water pipe
the magnet, which fits quite loosely inside the pipe, takes several
seconds to decend through that length of pipe.

What's happening is that the moving magnet's field induces a current
into the copper pipe and that current flowing through the copper creates
an opposing magnetic field which wants to keep the magnet where it is,
thus slowing its fall.

It's a simplified example of the resistance you can feel with your
fingers if you spin the shaft of a small permanent magnet DC motor with
and without it's power terminals shorted.

Jeff

--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
"What do you expect from a pig but a grunt?"