Two small identical metal balls of radius rare at a distance a `(a lt lt r)` from each other and are charged, one with a potential `V_(1)` and the other with a potential `V_(2)`. The charges on the balls are:

A large hollow metal sphere of radius R has a small opening at the top. Small drops of mercury each of radius r and charged to a potential V fall into the sphere. The potential of the sphere becomes V' after N drops fall into it . Then,

Two equally charged identical small balls kept some fixed disttance apart exert a repulsive force F on each other. A similar uncharged ball, after touching one of them is placed at the mid-point of line joining the two balls. Force experienced by the third ball is

Two equally charged identical small balls kept some fixed disttance apart exert a repulsive force F on each other. A similar uncharged ball, after touching one of them is placed at the mid-point of line joining the two balls. Force experienced by the third ball is

Metallic sphere of radius R is charged to potential V. Then charge q is proportional to

Metallic sphere of radius R is charged to potential V. Then charge q is proportional to

A hollow metallic sphere of radius 0.1 m is charged to a potential of 5 V. The potential at its centre is

Two identical thin rings, each of the radius R are coaxially placed at a distance R from each other. If Q_(1) and Q_(2) are the charges uniformly distributed on the rings, then calculate the work done in moving a charge q from the centre of one ring to the centre of the other.