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' MAGNETIC LEVITATION'
1999\09\28@062707 by Russell McMahon

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From: Anne Ogborn <spam_OUTanniepooTakeThisOuTspamNETMAGIC.NET>
>>This bring up an idea I had a while back.  Is it theoretically possible
>>to have a spherical magnet that has the north pole on the outside and
>>south on the inside?


>Nope -  div B = 0
>To evaluate any situation, mentally construct a closed surface. The net
>magnetic
>flux through that surface is 0. So, for example, your spherical magnet
>(which would have
>a uniform outward flux) could be enclosed by a larger sphere, and that
>larger sphere
>would everywhere have an outward flux. can't do it.
>If you try the ping pong ball experiment, you'll find that the lines are
>sharply curved, returning
>down between the individual magnets.
________________________________________



What you say is true, BUT, As I noted in my reply to this, what really
happens and what appears to happen are different and in this case (Murphy
must have gone on holiday) what APPEARS to happen is what matters. Y' canna
break the laws of Physics but, just sometimes, seeming to MAY BE good
enough.

Imagine.

First place bar magnets facing outwards along the main axes in both
directions with, say, Norths out.
Allow a gap in the middle for the Souths to have some separation from each
other. This takes 6 magnets.
Sniff around the outside of this with a hall cell or whatever. You will find
lots of North indicated with weaker spots in between . As long as you stay
outside the sphere mapped by the ends of the bar magnets you will still see
North poles - just of varying strength
Now insert North pole outward bar magnets in the "holes" at 45 degrees (in
every direction) from the existing magnets. You will need 8 bar magnets for
this making 14 in total.
Now with your sniffer you will see an amazingly smooth North pole anywhere
around the sphere.


Here's a cross section of sorts
Ive used n--s for the diagonal magnets and N-S for the main axis ones.
The diagonal set of 4 are leaning out of the page at 45 degrees (can you
tell :-)) and they are hiding another set behind them leaning into the page
at 45 degrees. There are two more unshown - one sticking out of the page
from the centre and one going into the page on the either side of the
centre.
8 (seen) + 4 diagonal extra + 2 perpendicular = 14


            N
      n     |      .n
         s S  s
N----S       S----N
         s S s
      n     |       n
             N

Questions:

- Outside the length of the bar magnets, would you see any South poles?
- Can you build this on a wire frame?
- If you placed this on a slightly concave bed of vertical bar magnets with
their North Poles all facing upwards, what would happen?
 (make it a continuous North pole with a slightly concave face if you wish.

The answers will to some extent depend on magnet sizes, gap sizes, magnet
strengths etc but, I believe, levitation is possible this way. Theory, by
the way, says that it is not. As I noted recently, I have seen SIMILAR
things done and have been told by someone who is usually reliable that they
have done  something equivalent to this. I must try it some day ;-)




Russell McMahon




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1999\09\28@092811 by Matt Bennett

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face
At 05:07 AM 9/28/99 , you wrote:
{Quote hidden}

Nope.  div B = 0 still.  What you get is a bunch of south piles that appear
to be
inbetween the north poles.  You will have an equal flux of North and South
poles
on your magnet ball. Think of the magnetic field as a continuous arrow
leading from the North to South pole.  Where the tail is pointing out, it is a
north pole, where it is pointing in, it is a south pole.  The lines have to
connect, unless you have a magnetic monopole- which are theorized, but have
never
been discovered.

There is a theorem (can't remember the name) that excludes the possibility of
pure, static, magnetic levitation.  There are exceptions, such as with a
spinning
magnet top (you've probably seen the toy).  When it stops spinning, it
falls down.
Another exception is above a superconductor- since it is an ideal conductor, a
magnetic field cannot exist inside it (the Meissner effect), so a
sufficiently small
magnet can levitate above it.  But don't get too strong a B field-  a very
strong
magnetic field will destroy superconductivity.

I have seen apparent levitation done with electromagnets, but there was a
somewhat
hidden sensor which controlled current to the electromagnet.

>
>Here's a cross section of sorts

...

>Questions:
>
>- Outside the length of the bar magnets, would you see any South poles?

As explained above, yes.

>- Can you build this on a wire frame?

Sure.

>- If you placed this on a slightly concave bed of vertical bar magnets with
>their North Poles all facing upwards, what would happen?
>  (make it a continuous North pole with a slightly concave face if you wish.

It would quickly roll off to the side.  Your concave bed of magnets don't
make a
truly concave field.  If you were to spin the magnet ball to give it some
stability
and a bit of restoring force, things might ge different, but it would not be
permanent levitation.  Once it stopped spinning, it would fall down.

>
>The answers will to some extent depend on magnet sizes, gap sizes, magnet
>strengths etc but, I believe, levitation is possible this way. Theory, by
>the way, says that it is not. As I noted recently, I have seen SIMILAR
>things done and have been told by someone who is usually reliable that they
>have done  something equivalent to this. I must try it some day ;-)



Please do.  But don't be suprised when it does not work.  But if it does-
keep it
secret and patent it.  You will be rich.  I'm not going to go so far as to say
Maxwell's laws are perfect or complete, but they do explain
electromagnetism as we
know it.

Matt Bennett

1999\09\28@131911 by Andy Kunz

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face
>The answers will to some extent depend on magnet sizes, gap sizes, magnet
>strengths etc but, I believe, levitation is possible this way. Theory, by
>the way, says that it is not. As I noted recently, I have seen SIMILAR
>things done and have been told by someone who is usually reliable that they
>have done  something equivalent to this. I must try it some day ;-)

Just saw a write-up the other day.  Someone has used superconductors to
create a true, functional magnetic levitation device.  I forget the
details, but you can probably find it using "superconductor" and "magnet"
as params.

Andy

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1999\09\29@011402 by Russell McMahon

picon face
>Nope.  div B = 0 still.  What you get is a bunch of south piles that appear
>to be
>inbetween the north poles.  You will have an equal flux of North and South
>poles
>on your magnet ball. Think of the magnetic field as a continuous arrow
>leading from the North to South pole.  Where the tail is pointing out, it
is a
>north pole, where it is pointing in, it is a south pole.  The lines have to
>connect, unless you have a magnetic monopole- which are theorized, but have
>never
>been discovered.


OK. Sounds like a challenge to me.
As I said, I'm not challenging the laws of Physics or Maxwell's excellent
attempts to codify part of them.
I'm just saying that practice doesn't always produce results that you would
expect.

SO

The magnets are on their way (100 thereof) from the person I mentioned who
said that he had built a levitating "train" system using this method.
I'll let you know the results.

A thought to go on with.
I followed your argument re the magnetic field lines appearing as a North or
South depending which direction you view them from.
But - hold a small but longish bar magnet North pole a fixed distance from
the South pole of a much larger and similarly shaped bar magnet.
Hold it which way you will (South tail out into space away from the larger
South, at 90 degrees to axis of large magnet, or with the small magnet
"along the lines of magnetic field" so that its South is pointed towards the
large North) the small North will be attracted with equal force to the large
South. The overall torque on the small magnet will vary. The overall force
on the magnet will vary - you COULD interpret this by saying the force at
the North pole has changed. Would you?



Stay tuned :-)
I'll let you know why I'm wrong in due course.  .



RM



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1999\09\29@230223 by Brian Kraut

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Yes, superconductors create very nice magnetic levitation.  So do electromagnets
and magets and gyroscopes.  My goal was a do nothing executive desktop gadget
with a magnet just hovering in space over a base.  The liquid nitrogen part of
supercondctors makes this difficult.

I have been off list for a few days and need to digest all that you, Russ,
Anniepoo, and everyone else has posted then re-evaluate weather I think it is
possible and the best way to do it.

I don't want to use a lot of bandwith responding to all the info I got, so
thanks to all that contributed with the usual helpfullness and professionalism I
have come to expect from you all.  Another fine example of how usefull you all
are and how much interest an OT post can generate in spite of what some might
say on OT posts.

Andy Kunz wrote:

{Quote hidden}

1999\09\29@232717 by Sean H. Breheny

face picon face
At 11:15 PM 9/29/99 -0700, you wrote:
>Yes, superconductors create very nice magnetic levitation.  So do
electromagnets
>and magets and gyroscopes.  My goal was a do nothing executive desktop gadget
>with a magnet just hovering in space over a base.  The liquid nitrogen
part of
>supercondctors makes this difficult.

I suppose that you wouldn't be satisfied by a pair of magnets with holes in
the center and with a wooden dowel running thru the middle? This will
levitate just fine,with the dowel providing the lateral stabilization.

Sean

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1999\09\30@165436 by Reginald Neale

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face
>At 11:15 PM 9/29/99 -0700, you wrote:
>>Yes, superconductors create very nice magnetic levitation.  So do
>electromagnets
>>and magets and gyroscopes.  My goal was a do nothing executive desktop gadget
>>with a magnet just hovering in space over a base.  The liquid nitrogen
>part of
>>supercondctors makes this difficult.
>
>I suppose that you wouldn't be satisfied by a pair of magnets with holes in
>the center and with a wooden dowel running thru the middle? This will
>levitate just fine,with the dowel providing the lateral stabilization.
>

There is also a device where a bar/cylinder magnet sits in a magnetic well
created by powerful magnets on either side. A long horizontal wire at one
end provides lateral stability. This is easy to build and it's a pretty
cool desktop toy. The suspended magnet bobbles around a little in response
to environmental vibration etc.

Seems like it should be possible to replace the wire with electromagnets at
each end in a feedback loop. Might try it some day.

Reg Neale

1999\09\30@220434 by Brian Kraut

picon face
Not interresting enough.  I was thinking a dish shaped base so you could kind of
roll it around while it is floating in the air.  Not to mention fascinating your
friends by passing things underneath it.

Sean H. Breheny wrote:

{Quote hidden}


' MAGNETIC LEVITATION'
1999\10\01@013707 by Russell McMahon
picon face
>There is also a device where a bar/cylinder magnet sits in a magnetic well
>created by powerful magnets on either side. A long horizontal wire at one
>end provides lateral stability. This is easy to build and it's a pretty
>cool desktop toy. The suspended magnet bobbles around a little in response
>to environmental vibration etc.
>
>Seems like it should be possible to replace the wire with electromagnets at
>each end in a feedback loop. Might try it some day.


This is exactly the same as the device which I described (but a much more
understandable description:-)) EXCEPT that in my device the horizontal wire
was replaced by a pointed wooden dowel with the point resting on a mirror.
Very impressive visually.

The idea of using electromagnets to control the horizontal dynamic stability
sounds an excellent one. This should be much easier and require lower power
dynamic fields than the normal dynamic vertical levitators.


     Russell McMahon
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1999\10\02@104022 by Wes Johnston

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<x-flowed>Last time I was in Germany at the Deutsches Museum in Munich, I saw a steel
ball about 1 inch in diameter suspended in a magnetic field.  The electro
magnet would come on full force and as the ball rose, it would interrupt a
light beam causing the magnet to switch off.  Very simple.  Very power hungry.


At 01:38 AM 10/2/99 -0300, you wrote:
{Quote hidden}

Wes
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1999\10\02@152854 by Wagner Lipnharski

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Wes Johnston wrote:
>
> Last time I was in Germany at the Deutsches Museum in Munich, I saw a steel
> ball about 1 inch in diameter suspended in a magnetic field.  The electro
> magnet would come on full force and as the ball rose, it would interrupt a
> light beam causing the magnet to switch off.  Very simple.  Very power hungry.

If instead a steel ball it was just a rod magnet, the power consume
would be sensible smaller, since the critical position to interrupt the
electro-magnet would be when the rod magnet is also acting its field
over the electromagnet itself, so canceling a lot of gravity effect.  An
interesting device could be done using a brushless dc motor coils, and
rotate the field, so the suspended magnet would rotate too... :)  A wide
assembly of those coils could make the suspended magnet not only rotate,
but move in an orbital shape since it will try to get out in its
tangencial vectors (centrifugal force).

Wagner.

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