Our mistake! Thanks for letting us know.
The length of the 2x4 boards doesn't really matter. The longer boards will
just elevate the whoe apparatus a little higher off the table. The only
qualification to this is that if you use 18" 2x4's, you only have 2" to play
with before the hanging coils start dragging on the table! And it's not a
good idea to shorten the length that the coils hang very much, since it's
easier to observe the swinging when the length is long.
The finer the wire, the more coils you can get in a compact space, and the
less the wire weighs for a given number of coils. But the finer the wire, the
higher the electrical resistance also. For 50 turns, the finer wire might
actually be better, since the resistance probably won't be significant for
that number of turns, and you'll have less mass to get swinging. (50 turns is
essentially a minimum. A few more probably won't hurt!)
Hope this helps. Let me know how things turn out, or if you have more
questions.
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