Simple Electroscope

Bore a hole through the lid of a jam jar and push a piece of copper wire bent into a hook through it. Hang a folded strip of silver paper, from which you have removed the paper, over the back. If you hold a fountain pen, comb, or similar object, which has been electrically charged by rubbing on the top of the wire, the ends of the strip spring apart.

On contact with a charged object, electrical charges flow through the wire to the ends of the strip. Both now have the same charge and repel one another according to the strength of the charge.