Creating a magnetic ring field question

[oliver102]

Hi there,

I'm attempting a science experiment to create a magnetic suspension field that can hold magnetic objects in place in mid air.

Since a Magnetic field isn't flat a single magnet would be pointless as the opposing object is continually sliding off it, so I looked at creating a ring field so that objects would get caught in a magnetic trap as gravity acted down on them.

I'm wanting to build a large one that can hold something substantial however I want to build a prototype first to make sure my little theory works.

The design for it is relatively simplistic, a disk of wood with a uniform sequence of holes in 3 rings going round it.

The magnets them selfs are neodymium rod magnets dropped into the housings so they are fixed, each one is 2mm wide and 8 mm long. I'm still calculating the spacing in order to generate the magnetic ring needed to apply 360 degree's of magnetic force to be able to hold something stationry as I know a single weak spot will cause it to collapse.

Anyone have any thoughts on improving this little experiment?

I studied maths not physics, magnetic fields are just something that fascinate me and I'd like to do some experiments with their applications.

Thanks

 

[f95toli]

It can't be done (unless you use a diamagnetic materials, such as superconductors).
There is even a theorem proving this: "[URL

 

[oliver102]

Can you suggest a Diamagnetic material that would work?

Just so I understand it, a common permanent magnetic field can support a diamagnetic plate can't it? Such as graphite, if dropped in a magnetic field should be suspended.

I only did a few weeks of electromechanics and didn't get to do much practical work to experiment.

 

[f95toli]

The only thing that would work is a superconductor; and if you use a type-II superconductor such as YBCO you don't even need a ring (due to the flux pinning).
But then you would of course need to cool it using for example liquid nitrogen or a pulse tube cooler so it is rarely a practical solution.

All normal diamagnetic materials are much too weak to support anything in the kinds of fields you can get from a permanent magnet.

Hence, there is a reason why you've never seen this in a commercial product.

 

[Drakkith]

Could you simply design it so that the magnets holding the object up are on the bottom and it sits in the well of a couple of others on the ground? Like have a center magnet on a base, with a couple of other magnets arranged around it but tilted inwards slightly so that the fields form a "cup" of sorts. Would this work?

 

[f95toli]

Could you simply design it so that the magnets holding the object up are on the bottom and it sits in the well of a couple of others on the ground? Like have a center magnet on a base, with a couple of other magnets arranged around it but tilted inwards slightly so that the fields form a "cup" of sorts. Would this work?

No, see Earnshaw's theorem above. It is quite literally impossible to create configuration where the object is stable.

 

[Drakkith]

No, see Earnshaw's theorem above. It is quite literally impossible to create configuration where the object is stable.

Ah ok, I see now. New suggestion: Use some kind of support or varying magnetic fields to hold it in place.