If the electric potential at a point on the surface of a hollow conducting sphere of radius $R$ is $V$,then the electric potential at a point which is at distance $\frac{R}{3}$ from the centre of the sphere is

$A$ pellet carrying a charge of $0.5\, C$ is accelerated through a potential difference of $2,000\, V$. What is the kinetic energy attained by the pellet?

The concentric spheres of radii $R$ and $r$ have positive charges $q_{1}$ and $q_{2}$ with equal surface charge densities. What is the electric potential at their common centre?

Two charges $q_1$ and $q_2$ are separated by a distance of $30\ cm$. $A$ third charge $q_3$,initially at $C$ as shown in the figure,is moved along the circular path of radius $40\ cm$ from $C$ to $D$. If the difference in potential energy due to the movement of $q_3$ from $C$ to $D$ is given by $\frac{q_3 K}{4 \pi \epsilon_0}$,find the value of $K$.

$A$ 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 $V$)

$A$ charge of $10\, e.s.u.$ is placed at a distance of $2\, cm$ from a charge of $40\, e.s.u.$ and $4\, cm$ from another charge of $20\, e.s.u.$ The potential energy of the charge $10\, e.s.u.$ is (in $ergs$)