Eddy Current - Tubes | Ngā Ngongo Aurere
A non-magnetic pellet falls quickly through a conducting aluminium tube but a magnetic pellet falls slowly.
- Electromagnetic induction: Faraday’s Law and Lenz’s Law
- Interaction between a moving magnet and the generated eddy currents causes drag
- Conversion of energy from one form to another
- Conservation of energy is a major emphasis
Te Reo Māori Version
These devices can be purchased at fairly reasonable cost but we can bring ours to your school if you are in the Wellington area. Drop first the non-magnetic pellet and then the magnetic pellet through the aluminium tube. The demonstration can be extended by dropping the pellets though a plastic tube and an aluminium tube with a slot cut along its length. If students are uncertain where the energy in the currents goes, give them a hint by showing Boil Up.
This demonstration uses rare earth magnets. You really can get a serious injury from large rare earth magnets. Care must be taken even with relatively small rare earth magnets such as the ones used here. Swallowing a rare earth magnet is particularly dangerous.
See the Eddy Current Drag resource for additional information.
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
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. See also a discussion of Induction Stoves.
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.