"Don Klipstein" wrote in message
...
In article , Steve wrote:

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what does it do??

They are magic, aren't they? Have you tried the drop a magnet down a
copper pipe trick?

The magnet moving down the pipe induces eddy currents. These eddy
currents produce an electromagnetic force that resists the movement of the
magnet (with respect to the pipe) and does so to an extent varying
directly with the speed at which the magnet is moving. This slows down
the magnet.

At least this is what I have heard.

And aluminum tubes do this also, just not quite as much as copper ones
do. And I have seen aluminum tube stock.

Most other metals do this less, but I imagine that iron and lead pipes
may slow the fall of a close-fitting "rare earth magnet" a little in
comparison to nonconductive pipes.


I imagine an iron pipe would slow its fall speed to zero.

;-)

ever since I was a child, magnets have held a fascination for me. I've been
....[snip]....
My question is does anyone know of other sources either for ...
magnets that I may be missing out on? ....

Every microwave-oven tube has TWO quite-strong cylindrical magnets.
You have to tear the tube apart to retrieve them, but if you'll stack
6-8 of them with opposing poles on a loose-fit wooden dowels with some
kind of stop on the ends, I'll guarantee you that any kid who sees the
toy will practically wear it out playing with it. (Even sitting on
the shelf it looks magical, what with the magnets "floating" in air.)

--Myron.
--
Five boxes preserve our freedoms: soap, ballot, witness, jury, and cartridge
PhD EE (retired). "Barbershop" tenor. CDL(PTXS). W0PBV. (785) 539-4448
NRA Life Member and Certified Instructor (Home Firearm Safety, Rifle, Pistol)

sci.electronics.design,sci.electronics.components, rec.radio.amateur.homebrew,
"Greysky" wrote:

ever since I was a child, magnets have held a fascination for me. I've been
collecting them ever since. It used to be that you could always scrounge
loudspeakers for Alnico magnets. Then when the newer ceramic magnets began
to be incorporated into loudspeakers, it became a challenge to remove them
from their enclosures without breaking them. Now, I have to admit, I am
having a ball collecting the new 'super magnets' - like the ones inside hard
drives. There are also cool cylindrical magnets that you can get from inside
the heads of VHS machines. My question is does anyone know of other sources
either for Neodymium 'duper magnets', or strong ceramic magnets that I may
be missing out on?

Like other posters, I've gotten some good ones out of some 5"
full-heght 30MB hard drives, and the ceramic donut magnets inside
microwave ovens. There are also some small, moderately strong
(apparently a step below Neodymium) magnets in many small
earphones/headphones (the kind for Walkman type portable stereos with
the 1/8" plug), that I've bought surplus for a dollar each. But some
of these have a little ceramic ring/donut magnet that's about next to
useless.

Magnets like these come closest to being perpetual motion
machines we have yet to make, and I'd hate to have some just wind up into
the trash because I didn't know they were there :-)

There's this fun link that was posted a few months ago.

http://www.houseofscience.com/ouch/ouch.html

Thanks.!

On Sat, 26 Jun 2004 17:56:26 -0400, Ben Bradley
wrote:

There's this fun link that was posted a few months ago.

http://www.houseofscience.com/ouch/ouch.html


Love it.

This has been a very interesting thread but now I have even more reason
(than my other unfinished projects or ideas) to not order some of these
cool magnets.

Please use caution with these ceramic type magnets,
they can shatter and can hurt adults or kids.

steve

wrote:

ever since I was a child, magnets have held a fascination for me. I've been
....[snip]....
My question is does anyone know of other sources either for ...
magnets that I may be missing out on? ....

Every microwave-oven tube has TWO quite-strong cylindrical magnets.
You have to tear the tube apart to retrieve them, but if you'll stack
6-8 of them with opposing poles on a loose-fit wooden dowels with some
kind of stop on the ends, I'll guarantee you that any kid who sees the
toy will practically wear it out playing with it. (Even sitting on
the shelf it looks magical, what with the magnets "floating" in air.)

--Myron.
--
Five boxes preserve our freedoms: soap, ballot, witness, jury, and cartridge
PhD EE (retired). "Barbershop" tenor. CDL(PTXS). W0PBV. (785) 539-4448
NRA Life Member and Certified Instructor (Home Firearm Safety, Rifle, Pistol)