CURIE EFFECT MAGNETIC HEAT ENGINE KIT

Curie Effect Magnetic Heat Engine Kit

Curie Effect Magnetic Heat Engine Kit

Introduction

The heat engine uses a principle of magnetism discovered by Pierre Curie. He studied the effects of temperature on magnetism. Ferromagnetism covers the field of normal magnetism that people typically associate with magnets. All normal magnets and the material that are attracted to magnets are ferromagnetic materials. Pierre Curie discovered that ferromagnetic materials have a critical temperature at which the material loses their ferromagnetic behavior. This is known as its Curie point.

Discussion

The heat engine works because of something called the Curie effect. The Curie effect describes how a magnetic material loses its ability to stick to a magnet when heated above a certain temperature. This temperature is called the Curie temperature, and varies with the material. The Curie temperature for iron is about eight hundred degrees Celsius. The Curie temperature for the inexpensive ceramic magnets is also quite high, which is why the candle flame or even the alcohol lamp does not affect them. The Curie temperature for the Canadian nickel is lower, about 631 degrees Celsius. This temperature is within range of the alcohol lamp, and almost possible with the candle. The Curie temperature for the Radio Shack rare earth magnets is 310 degrees Celsius, and the candle can reach this easily (not only because of the lower Curie temperature, but because the magnets are so much smaller than the nickel that they heat up faster, and have less unheated surface area).

As an example, a piece Candle of iron (Fe) at room temperature is strongly Figure 1 attracted to a magnet.

Heat the iron to a temperature of 770 C, which is its Curie Point, it loses its ferromagnetism behavior and it is no longer be attracted to a magnet. If we let the iron cool, it regains its ferromagnetic behavior and is attracted to the magnet again.

We can use this property to construct a small swinger type heat engine. The heat engine uses a nickel alloy wire that has a low Curie point, see drawing to right. When the wire is at room temperature it is attracted to the magnet, and swings close to the magnet. In this position, labeled B2 in the drawing, it is heated by the flame of a small birthday cake candle. When the material temperature reaches its Curie Point, it loses it ferromagnetism and falls away from the ...