Describe a pith ball electroscope. How can you use it to test whether a body is charged or uncharged?

Pith ball electroscope consists of a small pith ball suspended by a dry silk thread from an insulating stand.

To test whether a body is charged or uncharged, bring the body near the pith ball without touching. If the pith ball moves towards the body, the body is charged. But if the pith ball remains stationary the body is uncharged.