Two charge $ + \,q$ and $ - \,q$ are situated at a certain distance. At the point exactly midway between them

A solid conducting sphere having a charge $Q$ is surrounded by an uncharged concentric conducting hollow spherical shell. Let the potential difference between the surface of the solid sphere and that of the outer surface of the hollow shell be $V$. If the shell is now given a charge of $-3Q$, the new potential difference between the same two surfaces is......$V$

Ten charges are placed on the circumference of a circle of radius $R$ with constant angular separation between successive charges. Alternate charges $1,3,5,7,9$ have charge $(+q)$ each, while $2,4,6,8,10$ have charge $(-q)$ each. The potential $V$ and the electric field $E$ at the centre of the circle are respectively

(Take $V =0$ at infinity $)$

The two thin coaxial rings, each of radius $'a'$ and having charges $+{Q}$ and $-{Q}$ respectively are separated by a distance of $'s'.$ The potential difference between the centres of the two rings is :

There is a uniform electrostatic field in a region. The potential at various points on a small sphere centred at $P$, in the region, is found to vary between in the limits $589.0\,V$ to $589.8\, V$. What is the potential at a point on the sphere whose radius vector makes an angle of $60^o$ with the direction of the field ?........$V$

A table tennis ball which has been covered with conducting paint is suspended by a silk thread so that it hang between two plates, out of which one is earthed and other is connected to a high voltage generator. This ball