Experiments with magnetic levitation

Floating Ball

There are actually two experiments which involve an aluminum ball or hollow sphere which floats in the air.  These demonstrations do require some skill in assembly and winding coils. 

The first is where a hollow aluminum sphere is able to float above a single phase coil.  Eddy currents are the means by which the magnetic field within the ball will repel the magnetic field produced by the coil. Details are given in:

Propulsion without Wheels
E. R. Laithwaite
Hart Publishing Company
New York, NY  1968
see pages 180-186

The second is where a hollow aluminum sphere floats between two helical coils.   This is called the Kerst-Murray Levitator.  More information is given at:

Physics Demonstrations, A Sourcebook for Teachers of Physics
Julien C. Sprott
1996
see chapter 5 at http://sprott.physics.wisc.edu/demobook/chapter5.htm