Jumping Ring | Porohita Pēpeke
Introduction
Abstract
Electromagnetic induction causes an aluminium ring to jump.
Principles Illustrated
Electromagnetic induction, transformers, forces on currents in a magnetic field.
Content
Video
English version
Te Reo Māori Version
Instructions
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.
Other Information
Safety
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.
Related Resources
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 .
Credits
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
- The New Zealand map shown on the poster frame above is used with permission from www.nz.com.
- The transformer apparatus used in the development of this resource was provided by Onslow College . The photo of the transformer is from Central Park Substation in Wellington and was provided by TransPower.