If a charge is shifted from a low potential region to a high potential region,the electric potential energy

$A$ hollow metal sphere of radius $15 \,cm$ is charged such that the potential on its surface is $20 \,V$. Then, the potential at the centre of the sphere is (in $V$)

$A$ pellet carrying a charge of $0.5 \, C$ is accelerated through a potential difference of $2000 \, V$. The kinetic energy attained by the pellet is:

Twenty-seven drops of water of the same size are equally and similarly charged. They are then united to form a bigger drop. By what factor will the electrical potential change?

$A$ regular hexagon of side $10 \; cm$ has a charge $5 \; \mu C$ at each of its vertices. Calculate the potential at the centre of the hexagon.

The electrostatic potential $V$ at a point on the circumference of a thin non-conducting disk of radius $r$ and uniform charge density $\sigma$ is given by the equation $V = 4 \sigma r$. Which of the following expressions correctly represents the electrostatic energy stored in the electric field of a similarly charged disk of radius $R$?