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Author Topic: Why do coils of copper levitate?  (Read 13602 times)

Heronumber0

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Why do coils of copper levitate?
« on: 27/07/2007 17:44:20 »
Just browsing through this amazing site http://tesladownunder.com/index.html.

There are some amazing effects using Tesla coils.

However, he also levitates coils of wire simply by plugging them into a power supply - I think he said 6.5A of current.

How does this levitation work? And can we use this principle for flight?


 

another_someone

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Why do coils of copper levitate?
« Reply #1 on: 27/07/2007 23:00:56 »
Just browsing through this amazing site http://tesladownunder.com/index.html.

There are some amazing effects using Tesla coils.

However, he also levitates coils of wire simply by plugging them into a power supply - I think he said 6.5A of current.

How does this levitation work? And can we use this principle for flight?

I see reference on the site to what he calls 'lifters' - which fly in ion winds - but not sure where the coils of wire are - would you like to direct this lost fool to the right point in the site where is shows this happening?
 

Heronumber0

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Why do coils of copper levitate?
« Reply #2 on: 28/07/2007 01:31:49 »
I don't know if this is right but its under magnetic levitation where he shows coils levitating at the foot of the article.  I think the photographs show coils levitating over a copper plate. I think a current must be induced in the copper plate which behaves like a magnet of the same pole and the two items repel each other.

 I was wondering about a clip on the net where a scientist put a number of copper coils into the mains and showed the coils levitating. I just wondered what the scientific explanation was and if it is being used or not by the USA for UAV's (drones)
« Last Edit: 28/07/2007 01:43:48 by Heronumber0 »
 

another_someone

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Why do coils of copper levitate?
« Reply #3 on: 28/07/2007 01:43:06 »
OK, the coil is levitating above a copper plate, and so is inducing a current in the copper plate that creates a repulsive magnetic field.  This is how malev works, and is used to levitate trains, but useless for levitating something thousands of feet up in the air (besides which, having large magnetic fields like that is scarcely going to be regarded as stealthy - detect the magnetic field, and you know there is a UAV in the area, and a good idea where is it (not that it matters, since the UAV could only fly over a metal plate).
 

Heronumber0

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Why do coils of copper levitate?
« Reply #4 on: 28/07/2007 02:05:10 »
That's what I think Goerge (hope it is OK to call you by your name).  However, I am referring to an instance where a plug was attached to ome coils by a professor. He plugged it into the mains and it levitated. He said that this effect could not be explained but I am certain somebody can explain that phenomenon.  I could not find it on the Internet.
Frank
 

another_someone

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Why do coils of copper levitate?
« Reply #5 on: 28/07/2007 02:21:11 »
hope it is OK to call you by your name.

By all means.

  However, I am referring to an instance where a plug was attached to ome coils by a professor. He plugged it into the mains and it levitated. He said that this effect could not be explained but I am certain somebody can explain that phenomenon.  I could not find it on the Internet.
Frank

Difficult to judge without seeing the experiment in question.
 

Offline syhprum

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Why do coils of copper levitate?
« Reply #6 on: 28/07/2007 11:15:32 »
In the London Science museum they have an exhibit in the children's section  where you can levitate an aluminium dish over a mains powered electro magnet
 

lyner

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Why do coils of copper levitate?
« Reply #7 on: 29/07/2007 13:40:01 »
It's to do with the laws of electromagnetic induction.
The changing fields due to the electromagnet induce 'eddy currents', which are circular currents flowing around in the metal plate. Lenz's law tell us that the direction of the induced current is ' such as to oppose its cause' (my old text book's expression). Hence, they produce a field in opposition - producing a repulsive force.
Magnetic Levitation is used for some novel rail systems and in a few other applications. BUT, it needs very high fields. There is a 1N force on a 1m wire carrying 1A in a field of 1T. The Tezla (T) is the SI unit of Magnetic flux density (field) and is enormous. At any height above the Earth, the field would be very very small.
There is a classic  A level Physics question which asks students how much current the National Grid would have to carry in order to support the wires without towers, using the Earth's magnetic field. The answer is millions and millions of amps!
 

Heronumber0

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Why do coils of copper levitate?
« Reply #8 on: 29/07/2007 17:46:44 »
Sophie thanks for the reply.  I am now beginning to think that I dreamt this now.  However,if I am not in a living dream then I distinctly remember seeing a clip where a plug:

http://en.wikipedia.org/wiki/Image:F_plug.jpg

with a short length of wire will hundreds of coil was casually plugged into the mains and the coils then levitated automatically.

If I didn't dream this how did it happen?
 

Offline Rjim781

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Why do coils of copper levitate?
« Reply #9 on: 21/11/2007 03:28:33 »
It is true and easy to make. You can see a demo, get the equations and get a lecture on the subject by MIT professor Walter Lewin. See lecture 19 and 20 on the subject. Remember to use  a non-ferrous plate (Al or Cu).

newbielink:http://ocw.mit.edu/OcwWeb/Physics/8-02Electricity-and-MagnetismSpring2002/CourseHome/index.htm [nonactive]

Jim :)
 

lyner

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Why do coils of copper levitate?
« Reply #10 on: 21/11/2007 10:09:17 »
Part of the Standard School demonstration transformer kit. Griffin and George.  The one available these days is not as good as the beast I was shown when at School, myself. IT threw an aluminium ring up to the ceiling.
The same teacher boiled water in a glass beaker, using two nails connected directly to the mains. Health and safety or what???????
 

Offline wolfekeeper

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Why do coils of copper levitate?
« Reply #11 on: 15/02/2010 22:24:06 »
This is old hat:


Basically, all that happens is the magnetic field in the copper coil causes a current to be set up in the aluminium plate that opposes the changes in the coil. Because the coil's field is oscillating the two fields repel and levitation occurs.

(Actually, that's a slight simplification, the more accurate explanation involves inductance of the plate; there's absolutely nothing magical happening, and Finite Element Magnetics simulations show the lift effect quite well.)

The downside of this is that the coil gets very hot, very quickly.
 

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Why do coils of copper levitate?
« Reply #11 on: 15/02/2010 22:24:06 »

 

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