Question

How can you use the gold leaf electroscope to detect the nature of charge on a body?

Answer 1

A G.L.E can be charged positively or negatively by touching the disc of the G.L.E. with a positively charged glass rod or negatively charged ebonite rod. Only when the G.L.E is charged, will the leaves collapse or diverge depending on the charge of the body for which the type of charge is to be determined.
In order to identify the charge of a body we should use a charged electroscope. Let us say the electroscope is negatively charged. Now bring the unknown charged body 'X' near the cap of the electroscope. If the leaves diverge more the charge in 'X' must be negative. Suppose that the leaves close a little when 'X' is brought near 'C', then 'X' may have a positive charge or it may not have any charge.
In order to confirm the positive charge you must bring the rod 'X' near the cap of a positively charged electroscope. If the leaves diverge more, then 'X' has positive charge.
Below is the diagrammatic representation.