5K20.u1 - Lenz's Law - Induction Currents
Demonstrate induced currents by magnetic pumping.
Mount the rings so the students look at them edge on and there is room for the professor to use a magnet to induce current in the hanging rings.
When the ring has been stablilized, bring the hand magnet slowly up to the center fo the ring. "Pump" the hand magnet in and out of the center of the ring in harmony with the period of the ring and suspension. The ring will immediately begin to oscillate.
A variation to this is to suspend a solenoid and perform the same action to induce charge in the solenoid. The same pumping of the hand magnet will cause the solenoid to oscillate in response.