The Stable Levitation of an Iron Ball over a Ring Magnet

An iron ball floats in midair in a plastic tube when the plastic tube is coaxially inserted in a ring-shaped permanent magnet. A ring permanent magnet has a special paraboloidal interface around its axis, the magnetic field Bz is of negative value, and points down in the range Zlow. But it is of positive value and points up in the range Zup; it is 0 at Z0 position. The iron ball cannot be stable levitated over the ring magnet no matter it is in the Zlow or Zup regions; it is only possible to realize the stable levitation of the iron ball at Z0 position. Theoretical calculation and experiment have been done and identified the stable levitation of an iron ball over a ring magnet. It is helpful to design and develop new magnetic levitation system for practical applications.