An electroscope is a device used to detect the presence of charge and
it's relative amount. The electroscope is usually constructed with a metal plate or
sphere at the top of a metal post with thin foil leaves hanging from the bottom of the
post. This setup is typically supported in a flask or some other transparent
enclosure. If a charged object is brought near the top of the electroscope, the
leaves at the bottom spread apart. The greater the charge, the farther apart they
Electrons pushed by negative object toward the bottom of the electroscope.
The foil leaves at the bottom have a negative charge so they repel each other.