
Thus, the magnetic field must diverge out of the iron core since both axial and radial components are necessary for the effect. The radial magnetic field provides the Lorentz force. The axial magnetic field of the iron core is responsible for inducing the current in the ring. The Lorentz force between the magnetic field and the induced current propels the ring.

The changing magnetic flux induces an emf in the metal ring, producing a large current in the ring.

A conducting ring, placed over the ferromagnetic core of a solenoid, may levitate or jump off when the solenoid is energized with sufficient 60-Hz alternating current. The jumping ring is a vivid and popular demonstration of electromagnetic induction and is used to illustrate Faraday's and Lenz's laws. That's the simple "hand waving" explanation for the beginner student-a more accurate explanation follows.

A changing magnetic flux induces a current in a metal ring the magnetic field due to this current opposes the primary field, repelling the ring and flinging it into the air.
