The figure shows three circular arcs,each of radius $R$ and total charge as indicated. The net electric potential at the centre of curvature is

$A$ thin spherical conducting shell of radius $R$ has a charge $q$. Another charge $Q$ is placed at the centre of the shell. The electrostatic potential at a point $P$ at a distance $R/2$ from the centre of the shell is:

The electric potential inside a conducting sphere:

Three point charges $+Q$,$+2Q$,and $q$ are placed at the vertices of an equilateral triangle. The value of charge $q$ in terms of $Q$,so that the electrical potential energy of the system is zero,is given by:

An arc of radius $r$ carries a charge. The linear charge density is $\lambda$ and the arc subtends an angle of $\frac{\pi}{3}$ at the centre. What is the electric potential at the centre?

If four charges $q_1 = +1 \times 10^{-8} \text{ C}$, $q_2 = -2 \times 10^{-8} \text{ C}$, $q_3 = +3 \times 10^{-8} \text{ C}$, and $q_4 = +2 \times 10^{-8} \text{ C}$ are kept at the four corners of a square of side $1 \text{ m}$, then the electric potential at the centre of the square is: (in $\text{ V}$)