1000 small water drops each of radius r and charge q coalesce together to form one spherical drop.The potential of the big drop is larger than that of the smaller drops by a factor of :

Two equally charged small balls placed at a fixed distance, experience a force F.Asimilar uncharged ball after touching one of them, is placed at the midpoint of the two balls. The force experienced by this ball is :

Two concentric spheres of radius R and 2R have charges Q and 2Q. The potential at a point P situated at a point 3R/2 distance from common centre is V, now outer sphere is earthed, the potential at point P now is :

From a supply of identical capacitors rated 8 mF, 250V, the minimum number of capacitors required to form a composite 16 mF, 1000V is :

There are two concentric spherical conducting shells of radii r and 3r. The outer shell carries a charge q and inner is uncharged but connected to earth with a key which is open. Find the amount of charge flows from inner shell to earth when the key is closed.