A charged metallic ball is lowered into an insulated metal can.
The ball is made to touch bottom of the can, then it, is placed on the disc of electroscope shown below. Final observation must be
When charged metallic ball touches the bottom of can, all of its charge goes to the outer surface of the can. (Net charge on a conductor lies only on its surface). When ball is withdrawn from the can, it is uncharged. When ball is placed on the disc of electroscope, some charge flows from leaves towards ball. Thus, final charge on the leaves is reduced, so leaves of electroscope converges.