Magnet drops super-slowly through an eddy tube
A simple but cool science experiment.
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2 Posted 281 days ago by zf1 (moderator)
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.
3 Posted 281 days ago by peterpan007
they should do it through a longer and bigger tube with a bigger magnet of course
5 Posted 281 days ago by sp176
@#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.
10 Posted 280 days ago by zf1 (moderator)
#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.
11 Posted 280 days ago by Limberg
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
13 Posted 278 days ago by sp176
#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.
(46 votes)
1 Posted 281 days ago by primate1970
Cool..!
Gravity is a myth..... The earth sucks....!