Feel the Force

[Joe Gwinn]

I was playing with a pair of neo magnets (1" diameter by 0.125" thick from StewMac) mounted in an old drill-press vice, and I tried moving a handheld piece of 0.020" thick copper flashing sheet rapidly back and forth between the poles.

One can easily feel the eddy-current drag. It feels like the copper sheet is swimming in a vat of honey.

Aluminum also works, brass a little less so, and non-magnetic stainless steel (type 304) not at all.

[Magnut]

I love physics!

A neo sphere dropped through a copper pipe is really neat to watch too. I have done this trick for people while slyly exchanging the neo for a plain ball bearing that looked the same. Fun!

[belwar]

Now thats just cool. Im gonna have some fun with that tommorow.

[David Schwab]

I'd be interested to see how Nickel Silver compares to the other metals.

[Possum]

...

Make sure the door is closed so your wife doesn't catch you....."honey what ARE you doing?" I playing with my eddy currents sweetie.....

[Joe Gwinn]

I'd be interested to see how Nickel Silver compares to the other metals.

It will probably be like #304 stainless, as the skin depths are similar.

[peskywinnets]

Here in London our Science museum has a kiddie section, where they can run wild & learn absolutely nothing about science(!)...anyway, they have this well funky little unit - it's a toweresque thingymajig about chest high with a big open slot down the middle from top to bottom - either side of this slot is lined with magnets - the idea is to take a disc (they have several each made with different metal) & hold the disc at the top of the slot and let go - the copper & aluminium discs really do take an impressive amount of time to meander down to the bottom of the slot. It just doesn't look right...quite an optical illusion - nothing is touching these discs, but they're falling in slow motion.

I read the accompanying explanation - "eddy currents, blah blah, inducing, blah" ....all a bit unecessary, so I got some crayons & went on to spend a bit of time colouring in. (one day I hope to have some kids of my own & take them there too).


PS ...& don't get me started on the tiny bits of dry ice they were dropping onto water (in subdued lighting - all lit from the side)- akin to eddy currents in dry ice 'smoke' but - the end result transcended 'cool'!! ( http://farm4.static.flickr.com/3103/...1b9b9feff0.jpg )

[David King]

My 1/2" x 2" x 2" neo block will fall in slow motion from beneath a thick aluminum plate. It's really weird to try to slide it around, it definitely pulls the aluminum around with it. No end of fun. There are some kids working on a project to recover lost energy in semi trucks from going over bumps in the road. They must have used magnets in the shocks. They were able to regenerate 3% of the energy lost in an average trip. That's a huge amount. I think regenerative breaking only captures 5%...