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Magnetic magic.

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Jonzjob

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I have tries this with 3 small round 'rare earth' magnets, they are very powerful, and it really works. I used a piece of copper pipe about a yard long and it takes a couple of seconds to drop through.

Neodymium magnet in copper pipe

Faradays law came back to me from the dim and distant past :shock: I had not realised It would work quite so well?

While I was playing with the magnets I rolled them on my work bench and to my amaisement which ever way I rolled them they turned to face North South! I marked one end with a felt tip pen and the marked end always finished up facing North!. I thought that it must be some metal under the bench so tried it on another bench, then in the house on a table. Always stopped facing North even to the extent that if I rolled it with the marked end South it turned through 180º
 

AndyT

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Thanks for the reminder about this - when hands-on science exhibitions were new, Bristol had the 'exploratory' (since transformed into "@Bristol") and one of its exhibits was like this - I'm off to have a play!

You might want to use your magnet, an AA battery and a piece of wire to make a motor - like this - http://www.youtube.com/watch?v=zOdboRYf1hM
 

Jonzjob

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Sorry for the confustication Phil.

I had 3 of these http://www.axminster.co.uk/axminster-ra ... prod19790/ stuck face to face to form a 9mm thick by 10mm diameter cylinder. These were dropped through the pipe and as they drop they set up a small voltage which in turn sets up a magnetic field in opposition to the field from the magnets. This opposes the movement and slows the speed of the drop of the magnets.I hope that makes some sense to you :mrgreen:

Good ere init!! It's exactly the same principle that a generator uses to produce it electrificals

Faradays law http://en.wikipedia.org/wiki/Faraday%27 ... _induction. Something I learned 50 years or more back when I joined the R.A.F. as a Boy Entrant aircraft electrician :shock:
 

Jacob

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Getting back to the important things in life - a 2" bar rare-earth magnet is perfect for lifting the swarf from an oil stone. Saves oil and keeps things clean. You have then to get the swarf from the magnet but that's not difficult with a bit of old rag.
 

Jonzjob

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Oil stone? They are mucky aren't they? :shock: :shock:

I always use a DMT water stone. Always flat and cleans with a bit of paper towel :mrgreen: :mrgreen:

A bit of copper tube is always handy in case you drop a magnet, 'cause it doesn't drop so quickly do it :? :?
 

thick_mike

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If you look down the pipe you can see the magnets spinning in the opposing magnetic field. I trick the kids at school by doing the same thing with a plastic pipe. They rarely see the magnet I've concealed in the hand I'm holding the pipe with!!

Here's some more magnetic freakiness using ferrofluid:

http://m.youtube.com/watch?v=XUz1ZI-w6LQ

Ferrofluid is basically a liquid magnet.
 

SammyQ

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"I trick the kids at school "......

Never smile,
Never call them by their first name before Easter,
(Above) never tell 'em how it's done - just say 'page 245 of the textbook'


The entire advice of my first Head of Department.....a true survivor and practitioner, with none of this empathic/self-expression/holistic twaddle, just plain straightforward encouraging curiosity.

Sam, who started science-of-hand way back in 1981.
 

mailee

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Now that really is spooky! :shock: I have never heard of this before and just had to try it out after seeing the video.....it really works! :eek: Now can someone tell me in lay mans terms just how it does? (i read the Faradays law thingy but it all went over my head) :oops:
 

Kalimna

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Moving magnet in copper pipe causes moving electric current.

Moving electric current causes magnetic field.

Induced magnetic field (from copper/moving magnet/elec current) reacts with permanent magnet (neodymium metal lump) and slows permanent magnet.

Probably not 100% accurate, but (I think) near enough. It's a bit like saying "Quantum theory - please explain in laymans terms"..... :)

Adam
 

thick_mike

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Part of the reason that most people are fuzzy about how magnetism works is that they never teach it in schools. I had to wait until my chemistry degree second year to get an explanation, it's something to do with unpaired electrons and symmetry...but I can't for the life of me remember exactly!

In school we used to waffle on about domains, whatever they are!
 

Jonzjob

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Kalimna":2uw906v5 said:
Moving magnet in copper pipe causes moving electric current.

Moving electric current causes magnetic field.

Induced magnetic field (from copper/moving magnet/elec current) reacts with permanent magnet (neodymium metal lump) and slows permanent magnet.

Probably not 100% accurate, but (I think) near enough. It's a bit like saying "Quantum theory - please explain in laymans terms"..... :)

Adam
Seems to cause an echo toooo :mrgreen: Quote from me above

"I had 3 of these http://www.axminster.co.uk/axminster-ra ... prod19790/ stuck face to face to form a 9mm thick by 10mm diameter cylinder. These were dropped through the pipe and as they drop they set up a small voltage which in turn sets up a magnetic field in opposition to the field from the magnets. This opposes the movement and slows the speed of the drop of the magnets.I hope that makes some sense to you :mrgreen:
:lol: :lol: :lol:

Magnets and gyroscopes are fascinating..
 

Pete Maddex

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Jacob":2inientz said:
Getting back to the important things in life - a 2" bar rare-earth magnet is perfect for lifting the swarf from an oil stone. Saves oil and keeps things clean. You have then to get the swarf from the magnet but that's not difficult with a bit of old rag.
Hi, Jacob

Put the magnet in a plastic bag, smaller magnets you can put inside aerosol lid.

Pete
 

bugbear

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Pete Maddex":2lldhso9 said:
Jacob":2lldhso9 said:
Getting back to the important things in life - a 2" bar rare-earth magnet is perfect for lifting the swarf from an oil stone. Saves oil and keeps things clean. You have then to get the swarf from the magnet but that's not difficult with a bit of old rag.
Hi, Jacob

Put the magnet in a plastic bag, smaller magnets you can put inside aerosol lid.

Pete
Lee Valley sell a "quick release" magnet:

http://www.leevalley.com/US/wood/page.a ... 42356&ap=1

BugBear
 

bugbear

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Kalimna":1b9eynr7 said:
Moving magnet in copper pipe causes moving electric current.

Moving electric current causes magnetic field.

Induced magnetic field (from copper/moving magnet/elec current) reacts with permanent magnet (neodymium metal lump) and slows permanent magnet.

Probably not 100% accurate, but (I think) near enough. It's a bit like saying "Quantum theory - please explain in laymans terms"..... :)

Adam
A simpler way to justify it (even if the mechanism isn't obvious); if the magnet weren't slowed you'd get a current (in the pipe) for nothing, which would allow you to make a perpetual motion machine.

And (second time this week);

"Lisa, in this house, we obey the laws of thermodynamics!"


BugBear
 

thick_mike

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Electrons can be pushed or pulled with a magnet because they have a (negative) charge. The copper pipe is full of electrons that are free to move, so the falling magnet makes the electrons move.

Whenever electrons have a net movement in a particular direction (an electric current) a magnetic field is formed. That field happens to repel the magnetic field of the falling magnet, thus slowing its fall.
 
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