The reason we removed this from our snack list was not because the force
was too small, but rather that people could not reliably make a pivot for
their pendulums which would swing cleanly and easily and yet not collide
with the magnet.
We're waiting for inspiration aboout how to design a simple easy too build
precise frictionless (or low friction at least) pivot for our pendulums.
Neodymium magnets do work better than cow magnets by about an order of
>---------- Forwarded message ----------
>Date: Wed, 17 Sep 2003 16:29:37 EDT
>Subject: Magnetic pendulum
>I noticed that this snack was removed from your list of snacks. Was that
>because it does not work very well?
>I was reading a feedback from a father who was trying this project with his
>child. He complained that the effect was not great enough and attributed it
>to the type of wire he used. He had the very slightest effect using
>wire and not magnet wire. So how can the effect be increased? The
>magnetic induction causing the force apparently is not very strong. To
>object most readily, the mass to be moved must be very small. That would
>the coiled wire and the rod supporting the wire. For maximum effect you
>want more turns of wire. However, that increases the mass. So the lighter
>wire (smaller gauge) makes sense but so would a lighter support rod. The
>induced EMF in the wire also depends on the strength of the magnetic
>use a stronger magnet. A cow magnet is strong but not as strong as a
>neodymium magnet. They don't make cylindrical neodymium magnets as far as
>I know so
>you can't just drill a hole for the cow magnet but must find some way of
>mounting the rectangular neodymium magnet. Perhaps drill a series of
>holes and then
>use a chisel to knock out the rest of the wood forming a rectangular hole.
>The force should also depend on the rate at which the area is changing so the
>faster it swings, the better? So start the swing at least twice as high as
>the position of the secondary coil???
>I have never done this experiment but it sounds really neat. I did not see a
>response to the father who wrote the orginal email in 1998.
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