Ferromagnetic materials such as nickel, iron, or cobalt lose the electron alignment that makes them attracted to a magnet when sufficient thermal energy is added. The temperature at which this change occurs is called the “Curie temperature,” or “Curie point.” Nickel has a Curie point of 627 K, so a candle flame is a sufficient heat source. A simple but elegant device illustrates this phenomenon beautifully.
REFERENCES
1.
One source of pure 28-gauge nickel wire is Lightning Vapes (http://lightningvapes.com/). At time of publication a 25-foot roll costs $4.50.
2.
The support is made from a 4 × 4-in aluminum square with a 2.5 × 3-in corner removed. The magnet support is folded to a height of 1.75 in and the pivot support is folded to a height of 2.5 in. These dimensions fit a tealight candle as the heat source. The pair of magnets allows easy adjustment.
3.
Richard
Sutton
, Demonstration Experiments in Physics
, (Mc-Graw Hill
, New York
, 1938
), Experiment E-103, p. 291
.4.
George
Barnes
, “Demonstrating the Curie point in nickel,”
Phys. Teach.
24
, 86
(Feb. 1986
).5.
George
Barnes
, “Rotary Curie-point heat engine,”
Phys. Teach.
24
, 204
(April 1986
),© 2014 American Association of Physics Teachers.
2014
American Association of Physics Teachers
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