Diamagnetism & levitation of pyrolytic graphite explanation

[magnetics]

Hi,

This YouTube video shows various shapes of pyrolytic graphite suspended on an alternating polarity matrix of square neodymium magnets.

As I understand the principle of diamagnetic anisotropy, the stronger the external magnetic force, the stronger the induced repulsive force in the diamagnetic material. Hence the levitation.

But the pieces of pyrolytic graphite are orientating to settle on the magnet matrix in a way that has maximum exposure to the interpole boundary between each magnet. To me this is counterintuitive, because this is where the magnetic field on the z plane (perpendicular to the surface) is weakest. It is strongest at the centre of the magnet.

With this logic (that’s obviously incorrect) the square and round graphite pieces should centre on a square magnet, not sit so as to gain maximum exposure to the boundary where the magnetic poles are alternating.

Am hoping someone who understands the phenomena can explain why the pyrolytic graphite orientates the way it does on this alternating magnetic matrix?

Thank you.

 

[kuruman]

There are induced currents in the plane of the diamagnets that create a dipole moment perpendicular (normal) to the surface. If the normal to the surface is at an angle with respect to the magnetic field, there would be a torque that would restore the magnetic moment to be parallel to the surface. You can see the effects of the restoring torque in the video. When the diamagnets are bumped, the normal to the surface oscillates about the z-axis until the oscillations damp out.

 

[magnetics]

Thank you kuruman, unfortunately not sure I follow. Might need a little more educating :)
You mention, where the magnetic field (from the magnet matrix) is at an angle, is this mainly along the boundaries between the opposing pole magnets?
That is, where the square magnets abut, the magnetic field strength on the z-axis would be near zero while being their strongest on the x-y plane.

Not sure how the torque restores the magnetic moment to be parallel to the surface?

Thanks in advance.

 

[Willb1998]

I'm quite interested in electromagnetism and diamagnetics. Do you think if something being repulsed like a bismuth plate 6-12 inches wide was bolted to a base with all thread and the electromagnet was attached to the base would the whole apparatus go skyward? Most people think of a stationary base and something like a train being levitated above. Just wondering if the whole thing would go upwards or levitate including the base overcoming the mass.

 

[Ibix]

I'm quite interested in electromagnetism and diamagnetics. Do you think if something being repulsed like a bismuth plate 6-12 inches wide was bolted to a base with all thread and the electromagnet was attached to the base would the whole apparatus go skyward? Most people think of a stationary base and something like a train being levitated above. Just wondering if the whole thing would go upwards or levitate including the base overcoming the mass.

No it won't, because that would violate Newton's third law. It's the difference between trying to knock a guy over by pushing on his chest with your hands and trying to knock yourself over by pushing on your own chest with your own hands.

Note that violations of Newton's third law lead directly to perpetual motion machines, which are a banned topic here.

 

[DaveE]

Disclaimer, I haven't really thought about this, but here's an idea to pursue.
While the force may be greatest at the centers, this might be an unstable equilibrium, so the material can "fall off" the peak force due to the gradient. At the boundaries, there is a stable equilibrium because to move horizontally the graphite would have to be lifted higher. Yes, less force in the valley than at the mountain top, but it's stable.

Look at the video at 1:37 where he shakes the plate. The annular graphite edges tilt up as they move towards the center of the next magnet (I think).

 

[kuruman]

@Ibix gave essentially the answer that I was going to give. Therefore will just point out that what you are proposing is equivalent to levitating yourself off your chair by grasping your collar (use both hands if necessary) and pulling up. It doesn't work not because you are not strong enough, but because of Newton's 3rd law.

 

[Willb1998]

Thanks guys admin please don't ban me I'm new to the forum. I was just exploring the idea of levitation and flight with little to no noise compared to say a quadcopter which is a proven design. Maybe the biefield brown effect and ion wind is worth exploring instead. Indeed you you're right that the repulsive force can't cancel out the overall mass and down ward force. Otherwise the idea would have been done already.

 

[berkeman]

Thread closed for Moderation...

 

[Drakkith]

@Willb1998 I've split off a similar post of yours and the replies to it into it's own thread here: https://www.physicsforums.com/threads/electromagnetic-levitation.1061165/#post-7070804
Further discussion can take place there. In the future please don't make multiple posts about the same thing unless the content of those posts are different enough to warrant being placed in different threads.

Since this is a 6+ year old thread it will remain locked. Anyone wishing to discuss this topic should make a new thread. Thank you all.