Question

Given a plastic rod and fur, how would you charge the electroscope

Answer 1

If you rub a plexiglas rod with fur, the fur will gain a positive charge. If you now bring the fur close to the cap of a GLE, the leaves will open due to induced charges. If you now earth the GLE by touching the cap, electrons will flow up from earth and the leaves will close, because the GLE is at zero potential. If you now take away the fur, the leaves will open because the GLE is now negatively charged.