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Old 24th December 2004, 04:35 PM   #1
JoeBob is offline JoeBob  Canada
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Default A question on magnets and coils...

Ok, I was wondering, if I have a magnet in the shape of a cylinder, and a coil that is would so that the diameter of the center gap is slightly larger than the cylinder magnet, what would happen if I placed the cylinder magnet inside the coil and ran a current through the coil. AC current would then cause a magnetic filed in the coil, correct? So the cylindrical magnet would grepelled from the coils edges and stay "perfectly" in the center as well as being pushed in a direction (up or down), or be attracted to every edge of the coil and get sucked up or down, right?

I'm just not too sure on this. I'm trying to do something like that, have the cylinder weighted and have the coil standing up so that I can slowly turn up the amperage and find a point when the tube is held relatively steady.

I was just wondering how to do this, and I'm gathering my idea is flawed so far, just wanted input on it. Thanks...
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Old 24th December 2004, 05:04 PM   #2
markp is offline markp  United States
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Depending on the current used the coil will move further with more current because of the stronger field generated. If the freq used is too low then the coil will move too far to stay on the magnets center. If the freq is high is will not have enough time to travel very far and it will keep closer to the center. If you are trying to suspend something in midair with the coil, give it up. If it weighs anything it will take too much power and your coil will burn up.
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Old 24th December 2004, 07:48 PM   #3
Mark Kravchenko
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Default Beam me up Scotty

What you are sugesting is not easy. THe poles of your cylinder magnet meet in the middleand at very small distance from the middle start to get weaker or stronger. The power supply that you would need is an extremely finly variable DC supply or a custom high frequency AC supply to try and stay ahead of the natural tendency of the coil to repell up and down everytime there is a zero crossing (normally at 60 hz)

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Old 24th December 2004, 08:02 PM   #4
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Maglev isn't easy. Some situations can be mechanically stable, most need feedback to invert the 1/x^2 law governing the forces.

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Old 24th December 2004, 08:24 PM   #5
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Does this mean I have to give up on the idea of floating around the living room with a pocket full of magnets?
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Old 24th December 2004, 09:27 PM   #6
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Yes, unfortunately. However, all is not lost: simply butter a piece of bread and strap it to your cat's back (butter side up).



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Old 24th December 2004, 09:30 PM   #7
JoeBob is offline JoeBob  Canada
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Ah, I see how it would be rather hard. There goes my dream of having a floating turntable platter... Thanks for the info though.
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Old 24th December 2004, 11:08 PM   #8
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Quote:
Originally posted by Sch3mat1c
Yes, unfortunately. However, all is not lost: simply butter a piece of bread and strap it to your cat's back (butter side up).



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I don't get it.
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Old 25th December 2004, 07:23 AM   #9
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http://www.xs4all.nl/~jcdverha/scijo....html#subindex



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Old 25th December 2004, 07:36 AM   #10
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I am out of butter. Will olive oil work?
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