A metallic vessel is placed on a non-conducting stand. The inner and outer surfaces of the vessel are connected to two gold leaf electroscopes A and B respectively. A charged sphere suspended by a non-conducting string is slowly lowered in to the vessel. how do the leaves of the electroscopes A and B behave? How will the behaviour change if the sphere makes contact with the inner surface of the vessel?
The vessel is metallic,therefore electric field has to be zero inside.It depends on the charge that sphere is carrying.If sphere is carrying positive charge then inner surface of the metallic vessel will have negative charge induced on it and vice versa.
If the sphere makes contact with the vessel , then charge from the sphere will flow in the vessel till potentials of both are equal .