STEM Clubs

School: Hanham High School Status: In progress Date Started: 15 Dec 2009 Date Completed: 17 Dec 2013 Keywords tags: magnets ferromagnet engines curie point curie engine Physics Energy No of pupils: 1 Number of views: 682

A simple idea (but one that generates excellent opportunities for some small-scale design and construction work in variety of different media) could not be passed by when club leaders saw a clip of a "curie engine" in action on a web-site after discussing "magnetism" during a coffee-break and how they could make it more interesting for KS3 pupils (see You Tube and search for Curie Engine videos if your school hasn't blocked your access to such sites).

The Curie Engine takes its name from Pierre Curie who studied ferromagnetism, paramagnetism, and diamagnetism, and discovered the effect of temperature on paramagnetism which is now known as Curie's law. The material constant in Curie's law is known as the Curie constant. He also discovered that ferromagnetic substances exhibited a critical temperature transition, above which the substances lost their ferromagnetic behavior. This is now known as the Curie point.

Using this information it is possible to predict that heating a small magnet that is held in place by another (fixed) magnet's field it will lose its magnetism and will then be released. If the heated magnet is attached to a pendulum, after it swings away from the heat source, and cools slightly, it will be attracted back to the fixed magnet's field (as it falls below its Curie point). It will then be reheated and the cycle starts again. If you carefully balance the pendulum and heat-source, the magnet will oscillate continuously in and out of the magnetic field.

In our search for resources for this project the 2 main components (thickish copper wire and small magnets withs holes in them) were yet again discovered accidentally for very little money and/or for free. The copper wire was obtained from old 40 amp cooker cable wire that had been removed by builders and was no longer needed. The magnets, although originally sourced from scitoys.com, were obtained much more cheaply from a Grange homewares shop in the form of a girls bracelet-bead set (a princely 99p for one bracelet set containing 4 small clasp magnets).

The first attempt to create an engine can be seen in the video. The pendulum is "fixed" at 2 points (essentially the ends of the wire balance on the wood) but this creates the difficulty that if the magnetism is too strong the "pendulum" is pulled out of place. Pupils trailled both 2 point cradles and single point cradles fixed to a nail to find the best way to hold the heated magnet in place over its heat source.