Jumping Ring | Porohita Pēpeke
Electromagnetic induction causes an aluminium ring to jump.
Electromagnetic induction, transformers, forces on currents in a magnetic field.
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.
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.
Notes, Applications, and Further Reading
This teaching resource was developed by the Te Reo Māori Physics Project with support from
- Te Puni Kōkiri
- The MacDiarmid Institute
- Faculty of Science, Victoria University of Wellington
- School of Chemical and Physical Sciences, Victoria University of Wellington