A question on magnets and coils...
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 24th December 2004, 03:35 PM #1 JoeBob   diyAudio Member     Join Date: Nov 2001 Location: Montreal, Canada 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...
 24th December 2004, 04:04 PM #2 markp   diyAudio Member   Join Date: Oct 2003 Location: L.A., CA 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. __________________ If it sounds good... it is good!
 24th December 2004, 06:48 PM #3 mwmkravchenko   Mark Kravchenko diyAudio Member     Join Date: Jan 2002 Location: Perth Canada 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) Mark __________________ Mark www.kravchenko-audio.com
 24th December 2004, 07:02 PM #4 Sch3mat1c   diyAudio Member     Join Date: Jan 2003 Location: Milwaukee, WI Maglev isn't easy. Some situations can be mechanically stable, most need feedback to invert the 1/x^2 law governing the forces. Tim __________________ Seven Transistor Labs, LLC Projects and Resources / Electronic Design and Consultation
 24th December 2004, 07:24 PM #5 Bill Fitzpatrick   diyAudio Member     Join Date: Jun 2001 Location: Eugene, OR Does this mean I have to give up on the idea of floating around the living room with a pocket full of magnets?
 24th December 2004, 08:27 PM #6 Sch3mat1c   diyAudio Member     Join Date: Jan 2003 Location: Milwaukee, WI Yes, unfortunately. However, all is not lost: simply butter a piece of bread and strap it to your cat's back (butter side up). Tim __________________ Seven Transistor Labs, LLC Projects and Resources / Electronic Design and Consultation
 24th December 2004, 08:30 PM #7 JoeBob   diyAudio Member     Join Date: Nov 2001 Location: Montreal, Canada Ah, I see how it would be rather hard. There goes my dream of having a floating turntable platter... Thanks for the info though.
Bill Fitzpatrick
diyAudio Member

Join Date: Jun 2001
Location: Eugene, OR
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). Tim
I don't get it.

 25th December 2004, 06:23 AM #9 Sch3mat1c   diyAudio Member     Join Date: Jan 2003 Location: Milwaukee, WI __________________ Seven Transistor Labs, LLC Projects and Resources / Electronic Design and Consultation
 25th December 2004, 06:36 AM #10 Bill Fitzpatrick   diyAudio Member     Join Date: Jun 2001 Location: Eugene, OR I am out of butter. Will olive oil work?

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