Te Reo Physics Resources

Multimedia Physics and Science Teaching Resources


Boil-up | Tōrua Korohuhū


Electromagnetic induction is used to heat a copper ring and boil water.

Principles Illustrated
Electromagnets. Electromagnetic induction. How transformers combine electromagnets and electromagnetic induction to trade voltage for current or current for voltage. Energy transfer by transformers. Eddy current heating.



English version

Te Reo Māori Version


These devices can be purchased and are a lot of fun to use. We have just purchased a new one and can bring it to your school if you are in the Wellington area. Note in the video that the student pushes down on the iron bar that forms part of the core. This increases energy transfer and reduces the rather loud hum.

Read the instructions for the transformer carefully. These devices can be destroyed easily.

The transformer in one of its configurations
The transformer in one of its configurations

Other Information


The copper ring will get hot enough in a few seconds to cause a nasty burn.
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.

We have lots of eddy current resources. In particular, see the Jumping Ring demonstration that uses this same apparatus.

Notes, Applications, and Further Reading

Induction stoves use a combination of eddy currents and magnetic hysteresis to heat a pot. The stove itself does not get very hot at all! See http://en.wikipedia.org/wiki/Induction_cooker. NOTE: We do not take any responsibility for the content of external web sites. We often link to Wikipedia, for example, because we have found a lot of very useful material there. But remember that anyone can post anything on the web anytime, and web sites change over time as well. So check the information before you use it! If you find sources of information that are useful please let us know.


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