Capacity of an isolated sphere is increased $n$ times when it is enclosed by an earthed concentric sphere. The ratio of their radii is

In the figure a potential of $+ 1200\, V$ is given to point $A$ and point $B$ is earthed, what is the potential at the point $P$....$V$

The amount of heat liberated in the circuit after closing the switch $S$ .

Electric field at a place is $\vec E = {E_0}\hat i\,V/m$. A particle of charge $+q_0$ moves from point $A$ to $B$ along a circular path find work done in this motion by electric field

Two identical balls having like charges and placed at a certain distance apart repel each other with a certain force. They are brought in contact and then moved apart to distance equal to half their initial separation. The force of repulsion between them increases $4.5\,times$ in comparison with the initial value. The ratio of the initial charges of the balls is

Two spherical conductors each of capacity $C$ are charged to potential $V$ and $-V$ . These are then connected by mean of a fine conducting wire. The loss of energy will be