What is the electric potential at the center $O$ of a circle of radius $0.4 \ m$ with the charges arranged as shown in the figure?

If $20 \ J$ of work has to be done to move an electric charge of $4 \ C$ from a point where potential is $10 \ V$ to another point,where potential is $V \ V$,find the value of $V$. (in $V$)

Three identical charges of $10 \ \mu C$ are placed at the vertices of an equilateral triangle of side $10 \ cm$. The electrostatic potential energy of the system is ....... $J$.

$A$ charge $Q$ is uniformly distributed over a rod $AB$ of length $L$ as shown in the figure. The electric potential at point $O$,which is at a distance $L$ from end $A$,is:

The mass of a particle is $400$ times that of an electron and its charge is double that of an electron. The particle is accelerated by a potential difference of $5 \; V$. If the particle was initially at rest,what will be its final kinetic energy in $eV$?

The electric potential on the surface of a hollow sphere of radius $5 \ cm$ is $10 \ V$. What is the electric potential at its center?