Curie Point

Date: Mon Oct 22 2001 - 16:00:47 PDT

Hello --

>From what you've written, there are two possible things that come to mind:

The strand of small diameter steel wire sounds good, so the only other wire
problem would be the length. The shorter the length, the less resistance, and
the more current that will flow. Since it's current flow that makes the wire
get hot, the more the better. So one suggestion would be to shorten the wire,
if that's possible.

There are 2 different size 6 volt batteries. One has a "larger" rectangular
shape, about 3" x 5 1/2" (like the photo with the snack) when looking down on
it and the other has a smaller square shape. We've had situations where the
smaller one didn't produce enough current (this would be analogous to a D
cell vs. a C cell vs. an AA cell -- all are 1.5 volts, but in a short circuit
or very low resistance circuit, the larger battery is capable of delivering a
bigger surge of current -- and it will last longer in normal use). About a
year-and-a-half ago I retried the Curie Point snack with one of the larger,
rectangular 6-volt batteries (it was a Duracell, and unfortunately cost
somewhere between $15 and $20 as best I can remember) and got an initial
current of 7 amps, which made the wire glow and released the magnet in under
5 seconds. The current then dropped to about 4 amps as the wire glowed, since
the hot wire has more resistance than the cold wire. I don't think I've ever
tried a 12-volt battery, and it isn't feasible for me to do so at the moment,
so I can't really comment on it!

With respect to obtaining ferromagnetic materials to experiment with, you
might try The Magnet Source ( or 303-688-3966), 607 S.
Gilbert St., Castle Rock, CO 80104. They carry a variety of magnets, and
should be able to send you some sort of catalog or product list. Also, you
can look around office supply stores or at home for refrigerator magnets,
magnet strips, etc.

Hope this helps.

Don Rathjen
Exploratorium Teacher Institute

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