Daniel --
Glad you liked the electroscope. Sounds like the things that you were trying
to test were all electrically neutral, since you said all of them attracted
both the positively and negatively charged tapes. Neutral things will do
that. Neutural objects beome electrically polarized when near either a
positively or negatively charged object. The neutral object doesn't gain or
lose charge, but the negative charge it already has can be redistributed
somewhat so that it becomes generally farther away from a negatively charged
object (leaving the remaining positive charge closer) or generally closer to
a positively charged object. Both of these result in attraction.
Here are a few suggestions for charging objects to test with the tapes:
Rub styrofoam with wool -- styro will have a negative charge
Rub a balloon with wool or on your hair -- balloon will have a negative charge
We very recently found that the front of a color TV or computer monitor
screen seems to have a strong positive charge -- it strongly attracts the
"smooth" piece of the "tape sandwich" and strongly repels the "sticky" piece
-- we're still wondering about why, and still experimenting -- one person
remembers a black and white TV screen having a negative charge, but we
haven't retried that yet --
Hope this helps.
Don Rathjen
donr@exploratorium.edu
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