How can you tell that an electroscope has an electrical charge? can you tell from an electroscope alone what kind of charge it has?

An electroscope is a device which used to detect charge on an object. It consists of conducting sphere at top with a metal rod and metal leaves. This is enclosed in a glass jar. A charged object is brought near the top of the electroscope. this causes electrons to transfer to or from the charged object.

If the electroscope has charge, the leaves repel each other and move away from each other. This is because charge conducts from the metallic sphere through rod to both leaves. Having same charge, the leaves repel each other and open up. No change occurs in neutral state.

We cannot tell from an electroscope alone what kind of charge it has because the leaves have like charges and hence repel each other whether it is positive or negative charge. Thus, we cannot differentiate the charge.