A question on magnets and coils...

JoeBob · 24th December 2004, 03:35 PM

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...

markp · 24th December 2004, 04:04 PM

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.

mwmkravchenko · 24th December 2004, 06:48 PM

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

Sch3mat1c · 24th December 2004, 07:02 PM

Maglev isn't easy. Some situations can be mechanically stable, most need feedback to invert the 1/x^2 law governing the forces.

Tim

Bill Fitzpatrick · 24th December 2004, 07:24 PM

Does this mean I have to give up on the idea of floating around the living room with a pocket full of magnets?

Sch3mat1c · 24th December 2004, 08:27 PM

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

JoeBob · 24th December 2004, 08:30 PM

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 · 24th December 2004, 10:08 PM

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.

Sch3mat1c · 25th December 2004, 06:23 AM

http://www.xs4all.nl/~jcdverha/scijo....html#subindex

Tim

Bill Fitzpatrick · 25th December 2004, 06:36 AM

I am out of butter. Will olive oil work?

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 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

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 __________________ See my Electronics webpage -- the home of Vacuum Tube Drag Racing. The key to being a successful Audiophile: "I reject your reality and substitute my own!"

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 __________________ See my Electronics webpage -- the home of Vacuum Tube Drag Racing. The key to being a successful Audiophile: "I reject your reality and substitute my own!"


	Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

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, 08:30 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.

25th December 2004, 06:23 AM	#9
Sch3mat1c diyAudio Member Join Date: Jan 2003 Location: Milwaukee, WI	http://www.xs4all.nl/~jcdverha/scijo....html#subindex Tim __________________ See my Electronics webpage -- the home of Vacuum Tube Drag Racing. The key to being a successful Audiophile: "I reject your reality and substitute my own!"

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?

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Magnets, Magnets,Magnets!	skooter	Car Audio	10	25th September 2008 08:30 PM
Where to buy magnets	Tenson	Multi-Way	1	16th May 2007 12:47 AM
Question about field coils	454Casull	Multi-Way	1	24th October 2005 06:25 PM
series coils=more efficient? (atlas 15 question)	xstephanx	Subwoofers	18	1st March 2005 01:27 PM

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read