Electroscope

Electroscope is a device used to detect electric charge in an object

Construction

1. Take a glass container
2. Cover the glass jar with a cardboard and make a small hole in it to insert a metal wire or a metallic paper clip.
3. Insert a metal wire or a metallic paper clip inside it
4. Attach two metal plates (like -  aluminium foil leaves) on the end of the wire/paper clip which is inside the glass jar as in figure. 
5. The end of the wire/clip which is outside the jar is used to measure electric charge

Working

1. Bring a charged object in contact with the end of the wire/paper clip which is outside the jar.
2. The charges get transferred by the metal wire/paper clip since it is a good conductor.
3. The same charge gets transferred to the aluminium foil leaves.
4. Since both the aluminium foil leaves will be of the same charge, they repel each other. This would confirm the presence of charge on the object.