Question

to find nature of charge of an object,which electroscope is used - charged or uncharged?

Answer 1

To find out the nature of the charge in an object, you will need a charged electroscope. The electroscope is charged by touching its disc with a charged body; negative if want it to be charged negatively and positive charged body if you wan it to be charged positively. 

This is the test:

Bring the test object close to the disc of a charged electroscope. If the object has similar charge as that of the electroscope, then divergence of the leaves will increase. On the other hand, if the charge is opposite to that of the electroscope, the divergence will decrease.