A conducting ring is placed onto the protruding ferromagnetic core of a coil. When an AC current is applied to the coil the ring will fly off of the apparatus. While Lenz's law is often cited as the reason for this behavior, Lenz's law is insufficient to describe the force on the ring. One may show that a ring with a gap will not jump when current is applied. One may also show that a ring cooled with liquid nitrogen will jump much higher than one at room temperature.

If the cooled ring will not hit the ceiling, assure that current is being applied long enough and that the ring is taken directly from liquid nitrogen which has stopped boiling and launched. For the CENCO apparatus, the pink lines on the iron core mark range of placement where the aluminum ring has been made to hit the ceiling. Also, a foot switch is best for launching rings, while a Variac is better for showing relation between input voltage and the force on the rings.

K4, I2, A0

PIRA DCS 5K20.30