Te Reo Physics Resources

Multimedia Physics and Science Teaching Resources


Jumping Ring | Porohita Pēpeke


Electromagnetic induction causes an aluminium ring to jump.

Principles Illustrated
Electromagnetic induction, transformers, forces on currents in a magnetic field.



English version

Te Reo Māori Version


The transformer is assembled as shown above. Simply turn on the power and watch the ring jump. For level 2 physics, a demonstration of the force on a current carrying wire might be better done with the jumping wire demonstration. But this one is more fun, so perhaps do both.
Read the instructions that come with the transformer carefully. These devices can be destroyed easily.

Transformer frame
The transformer in one of its configurations
Transformer frame
The transformer in one of its configurations

Other Information


Once cooled in liquid nitrogen, the ring must be handled carefully with tongs. A metal ring cooled to -195 C can do a lot of damage if it sticks to your hand. Also, the ring flies up pretty fast. The operator and students should wear safety goggles and students should stand well clear of the apparatus. This demonstration particularly needs to be tested a few times by the teacher before class.
Liquid nitrogen should be handled only by properly trained individuals using standard safety procedures and safety gear. Everyone in the room should be wearing goggles any time liquid nitrogen is used for example. If you are not experienced, trained, and confident with liquid nitrogen, ask a nearby university physics department for help.
Individual teachers are responsible for safety in their own classes. Even familiar demonstrations should be practised and safety-checked by individual teachers before they are used in a classroom.

Transformer at Central Park Substation in Wellington

Boil Up

Notes, Applications, and Further Reading

Eddy current drag is used to make brakes in certain applications. See for example the following exchange on physlink: eddy currents brakes . Also see a discussion of eddy currents in Wikipedia .


This teaching resource was developed by the Te Reo Māori Physics Project with support from