5K20.30 • Eddy Currents: Jumping Ring

Location: Cabinet 4

Photo Shows the Demo Used by the University of Texas at Austin.

Instructions / Notes:

• Liquid nitrogen will no longer be provided.
• This demo is also referred to as Thompson's Jumping Ring.
• Two aluminum rings, one with a thin slit cut out and other being solid all the way around, are place around the core a large coil.
• With a ring in place, turn on the switch. The solid ring made of aluminum will fly upward.
• You may want a student to try to hold the solid ring down. It warms up quite quickly.
• The ring with a slit cut out of it does nothing.
• A secondary coil with a light bulb is provided to show the apparatus can function as an AC transformer.
• Prolonged operation will definitely trip the circuit breaker on surge protector / power strip mounted to the the table.

Demo Staff:

• Do not test inside the lab! Flies very high. Only test inside the lecture hall. Be careful of people when testing.

Last updated on June 8, 2026