Magnet drops super-slowly through an eddy tube

A simple but cool science experiment.

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Comments

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Picture of primate197033 achievements

+18 1. primate1970 commented 15 years ago

Cool..!

Gravity is a myth..... The earth sucks....!
Picture of zf140 achievements

+10 2. zf1 commented 15 years ago

im not sure exactly how this works but this is one possibility:

when the magnet falls through the copper tube, the magnetic field stimulates the movement of electrons within the copper. this temporarily creates an alignment of magnetic energy within the field of electrons (because electrons have their own magnetic field) which as a whole becomes a much stronger magnetic force than without the alignment. this in turn creates an attractive (or repulsive) force which slows down the magnet as it falls through the tube.


a similar effect would also occur with a diamagnetic material like bismuth or aluminum. in this case the physics work completely different. as the magnet falls through the tube, the magnetic energy is reflected my the diamagnetic material and back onto the magnet. the same polarity magnetic field creates a repulsive force which slows the magnet as it moves through the tube.
Picture of peterpan00724 achievements

+4 3. peterpan007 commented 15 years ago

they should do it through a longer and bigger tube with a bigger magnet of course
Picture of dvh35 achievements

+18 4. dvh commented 15 years ago

Picture of sp17625 achievements

+6 5. sp176 commented 15 years ago

@#3 a longer tube would only prolong the affect and would have no change in speed.

Bigger magnets would be counter-productive because magnetic strength is based by distance. For what you are thinking, you would need the copper tube and magnet to be closer, and to "fit" better.

As #4 points out this is ruled by Lenz law, and even a stronger magnet would be unable to counter the force of gravity because the coefficient of magnetism vs gravity will always be less than 100%. A stronger magnet (with same mass) will decrease the speed exponentially but never stop.

If you wanted to overcome gravity, you would need to apply an external emf to the copper tube.
Picture of Daire36 achievements

+4 6. Daire commented 15 years ago

thank god for Wiki >:)
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+2 7. 95731 commented 15 years ago

Wat if the magnets just wont go down XD
Picture of Smurfed18 achievements

+4 8. Smurfed commented 15 years ago

I don't care how it works, that was fucking sick!!
Picture of DarkiKun41 achievements

+3 9. DarkiKun commented 15 years ago

interesting =) gotta love science.
Picture of zf140 achievements

+1 10. zf1 commented 15 years ago

#4, #5 the lenz law only describes how the north and south poles of a magnet induce the directional flow of electrons within a copper coil.

this may give some insight on to how the directional flow of electrons are creating the levitating effect but it doesnt actually explain anything regarding to this tube experiment. its main application would be in things like dc turn generators, dc electric motors, etc.
Picture of Limberg43 achievements

0 11. Limberg commented 15 years ago

Thank you dvh #4, here is the "video" link from the wiki wich explains the experiment : http://www.magnet.fsu.edu/education/tutorials/slideshows/eddycurrents/index.html
Picture of MsZoomy34 achievements

+2 12. MsZoomy commented 15 years ago

science is cool!!
2 :(|) :(|) Monkey Heads
Picture of sp17625 achievements

0 13. sp176 commented 15 years ago

#10 You need to read up on your Lenz law, because that doesnt describe influence of polarity. You are thinking of Faraday's law. It does not matter if the positive is facing up or down the tube, if the tube has no external emf applied.

Lenz's Law states that the induced emf and the change in Flux linkage has opposite directions.