Curie Point

From: Pamela Federman (
Date: Tue May 02 2000 - 14:19:42 PDT

My 5th grade son and I tried the Curie Point experiment many many
times. Here's what works, and what doesn't:

First -- after 10+ stores of all kinds, we gave up trying to find pure
iron wire. (We tried bailing wire, piano wire, picture hanging wire,
florist wire, clock repair wire, etc.) Everything these days is steel,
and most steel is galvanized. Best bet is a craft store (Michaels) or
florist's shop -- we used 30 gauge non-galventized (not shiny, no zinc
coating) steel wire. (If anyone out there knows where to buy soft iron
wire, please e-mail us: THANKS.)

Second -- forget the battery and Radio Shak leads (we completely used up
4 batteries and burnedd out 2 sets of leads). The battery gets plenty
hot, but never heats the wire hot enough. We tried the heavy-duty Radio
Shak leads, but apparently the amount of heat created was enough to
create shorts in them. Putting the leads closer together only causes the
magnet to be attracted to the leads rather than to the wire.

Next, we tried candles to heat the wire -- forget that, too.

Finally, we stumbled on a hot air gun (used in crafts) at a school
supply store (Morrison's in San Carlos). You may also be able to get one
at a crafts store. They cost about $35. These blower works and sounds
like a hair drier, but has a more concentrated air stream and the
ability to produce hot air in the 600 degree Farenheit range.

We had to replace the string with soft wire, because the magnet got so
hot that it burned through the string. Also, the hot air stream is hot
enough to melt the Tinkertoys, so we had to make the assembly much
larger and the wire much longer so that none of the plastic parts were
anywhere near the hot air.

We aimed the air from above and slightly in front of the magnet (so the
air would not push much on the magnet), directly at the point at which
the magnet touched the wire. (Put a thick cutting board underneath the
experiment to protect your table surface.) It took only about 45
seconds to heat the wire to the Curie point, at which point the magnet
jumped to the air gun, which has a metal tip! We eventually found a
good angle and distance to allow the experiment to work properly.

We believe the magnet was partially demagnetized by the experiment --
it, too, got very hot. So since my son's experiment involved heating
different wires of different materials and gauges, we needed to use a
different magnet each time.

Note to the Exploratorium scientists: Does anyone actually try these
experiments before you post them? What was intended as a 1 hour science
experiment became a two weekend, 12 hour project as we tried to
troubleshoot all the problems that occurred with the original design!

By the way, the "what's going on" explanations were great.

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