Electromagnetic Ring Launcher

Quick Answer: The Electromagnetic Ring Launcher is a jumping-ring demonstration of electromagnetic induction. The listing image shows a red base housing the coil, an iron core rising through a clear guide tube and a metal ring placed over it; when alternating current flows in the coil, the ring is thrown upward or hovers on the core.

Inside the Jumping Ring

This electromagnetic ring launcher is a version of the jumping ring devised by Elihu Thomson. Alternating current in the coil sets up a rapidly changing magnetic field that the iron core carries up through the ring. The changing flux induces a large current around the ring, and because the ring’s current lags behind the coil’s, the force between them is mostly repulsive. At switch-on the repulsion is strong enough to launch a light ring up the tube.

If the current is left on, the ring can settle at a height where the average upward force balances its weight, and it floats on the core. The induced current warms the ring, and the coil warms too, so hovering demonstrations should be kept short. A ring with a saw cut across it does not move at all, which proves that a complete circuit around the ring is essential.

The unit in the image is connected by a mains lead, so it should be operated by a teacher or under close supervision, on a dry bench, with the rating on its label checked before connection. The rings included and the supply rating should be confirmed when ordering.

Care & Handling

• Operate the switch in short bursts; long running heats the coil and the ring.
• Keep faces and hands away from the top of the guide tube while a ring is launched.
• Handle rings only after the power is off and they have cooled.
• Inspect the mains lead and plug before each use and withdraw the unit if either is damaged.

Specifications

Applications

• A dramatic introduction to electromagnetic induction and Lenz’s law
• Comparing a solid ring with a split ring
• Discussing induction hobs, magnetic levitation and eddy current forces
• Science open days and assemblies where a visible, memorable effect is wanted

Why Choose LabEquip

Physics teachers and outreach presenters buy the ring launcher because the moment the ring leaps is something no student forgets. LabEquip lists it within the STEM kits range, and it pairs well with the Lenz’s Principle Verification Apparatus, which shows the same opposition slowly with a hand-held magnet. Enquire through our contact page.

Frequently Asked Questions

Why does the ring jump when the current is switched on?

The coil’s changing magnetic field induces a current in the ring. That induced current creates its own field opposing the change, so the ring and coil repel. The sudden rise in current at switch-on gives the largest push and sends the ring up the tube.

Why does a ring with a cut in it stay still?

The cut breaks the conducting path, so no current can circulate around the ring. Without an induced current there is no opposing magnetic field and no repulsion, even though the ring sits in the same changing field.

Can the launcher work on direct current?

A steady direct current produces a constant field, which induces nothing. Only the brief change at the moment of switching on would give a small kick. Alternating current keeps the field changing all the time, which is what makes continuous hovering possible.

Why does the ring become warm?

The induced current flows through the resistance of the ring and turns electrical energy into heat, just as in an induction hob. The longer the current runs, the warmer the ring gets, which is why demonstrations should be brief.

Why can the ring hover instead of flying off?

With the supply left on, the repulsive force weakens as the ring moves up and away from the coil. At some height the average force equals the ring’s weight, and it floats there. A lighter ring or a stronger current makes it hover higher.

What safety precautions apply?

The unit is mains powered, so check the lead and plug first and keep liquids away. Do not look down the tube or lean over it during a launch, run the coil only in short bursts, and let rings cool before students handle them.

Last Updated: September 2026