A short electric dipole is placed at the origin with its axis along the x-axis. If the dipole moment is $p$, the locus of points where the electric potential is zero is given by:

Two capacitors having capacitances ${C_1}$ and ${C_2}$ are charged with 120 V and 200 V batteries respectively. It is found that by connecting them together the potential on each one can be made zero. Then

Twenty seven drops of same size are charged at 230 V each. They combine to form a bigger drop. Calculate the potential of the bigger drop.