Dear Rob,
If you've got the motor working as it should, the coil should spin
continuously (until the battery finally goes dead!). In practice sometimes
it's a little erratic, but it should certainly do more than just spin a few
times. Notice that the discussion of the battery in the Materials section of
the snack says that the motor may work on a single 1.5 volt D-cell, but that
if it doesn't, you should try additional batteries (the introductory photo
shows 2 D-cells in series -- you can also try a 6-volt lantern battery or a
power supply). The motor may require a pretty reasonable current, especially
if the coil isn't extremely well balanced. Lemon batteries or vinegar
batteries can give voltages comparable to D-cells, but they won't give much
current, and I wouldn't expect them to be effective in running this motor.
They have more potential for success for very-low-current devices such as
some piezo buzzers, LED's and liquid crystal clocks. Hope this helps.
Don Rathjen
Exploratorium Teacher Institute
donr@exploratorium.edu
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