The work done in carrying a charge $Q$ once around a circle of radius $r$ about a charge $q$ at the centre is

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 $5\, cm$ is charged so that the potential on its surface is $10\, V$. The potential at the centre of the sphere is.....$V$

The charge given to a hollow sphere of radius $10\, cm$ is $3.2 \times 10^{-19}\, C$. At a distance of $4\, cm$ from its centre,the electric potential will be

Two points $P$ and $Q$ are maintained at the potentials of $10 \ V$ and $-4 \ V$,respectively. The work done in moving $100$ electrons from $P$ to $Q$ is

Choose the $CORRECT$ option.