Inspiring experiments exploit strong attraction of magnets

Figure 11. Demonstration of the Curie temperature.
ring magnet is suspended on a swing cradle made
of thick copper wire, which is in turn suspended on
a frame of the same copper wire. This small magnet
is attracted to a larger, fixed neodymium magnet
(25 × 5 mm). When the candle is lit, it heats up
the small magnet, which then loses its magnetism
and falls back with the swing in the vertical position.
This, however, takes it out of the flame and
enables it to cool, be remagnetized and attracted
once more to the larger magnet. Here it is again in
the flame, so it heats and loses its magnetism again,
F RONTLINE
and the cycle repeats. The overall size of my demonstration
can be seen from the size of the tealight
used. Considerable testing is required to produce a
reliable demonstration.
Safety warning
Neodymium magnets are dangerous because of their
strength and the fact that they shatter easily. They
should not be given to children to use unsupervised.They
should be kept away from electronic
apparatus and the magnetic strips on bank cards.
References
Featonby D 2005 Phys. Educ. 40 505–8
Neodymium magnets are available from
www.powermagnetstore.co.uk
www.sci-toys.com/scitoys/electro has
instructions about how to construct a number of
<strong>experiments</strong> using neodymium magnets
www.wondermagnet.com also has some
interesting <strong>experiments</strong>
www.amasci.com/neodemo.html includes some
neodymium demonstrations
David Featonby, North East Teacher Network
coordinator.