electroscope
...es a change in its net charge and causes the leave to repel each other. The electroscope can also be used to identify an unknown charge. First the electroscope must be negatively or positively charged by conduction. This causes the leave to repel slightly. If the unknown charge is like that on the electroscope, when it is brought near the sensor the leaves will move farther apart, but if it is opposite that on the electroscope, the leaves will move to their neutral position. How to Make An Electroscope Procedure Strip 3 cm off the ends of a piece of insulated wire. Make a J-like hook out of the uninsulated electrical wire. Place a Christmas tree icicle aluminized (shiny) side down over the hook. Make sure there is an even amount of material hanging on each side of the hook. Lower the hook with the icicle into the jar. There should be about 5 cm of wire sticking out ...