Magnetic levitating spinning top

  • #1

Main Question or Discussion Point

I was watching a youtube video about a magnetized spinning top, floating over a magnetic bottom.
I was wondering why this only works when the spinning top is spinning?
Can't a magnetic field be stable?
Would it still work with a stillstanding top, and the magnetic bottom rotating?

If you could explain some of the theory, or direct me to some online reading, it would be much appreciated.

Thanks in advance
Daniel
 

Answers and Replies

  • #2
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I'm going to refer you here: http://en.wikipedia.org/wiki/Spin_stabilized_magnetic_levitation
Earnshaw's theorem does not allow for a static configuration of permanent magnets to stably levitate another permanent magnet or materials that are paramagnetic or ferromagnetic against gravity. This theorem does not apply to devices consisting of a properly configured magnetic base and corresponding top, however, because the non-static nature of the spinning top acts as a gyroscope to prevent its magnetic field from aligning itself in the same direction as that of the magnetic base (i.e.: via the top flipping). This gyroscopic property combined with the top's precession allows it to respond dynamically to the direction of the local toroidally shaped field of its base magnet and remain levitating about a central point in space above the base where the forces acting on the top (gravitational, magnetic, and gyroscopic) are in equilibrium thereby allowing the top to rest in an energy minima well.
Basically, the gyroscopic forces stabilise the magnet preventing it's magnetic field lines lining up with those of the base.

I didn't know this and so have learnt something also. Very interesting.
 

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