$A$ spherical shell of radius $5 \ cm$ is charged to a potential of $10 \ V$ on its surface. The potential at the center of the shell will be ...... $V$.

$A$ point charge $q$ of mass $m$ is placed at the center of a ring of radius $R$ carrying a charge $Q$. When it is slightly displaced,the point charge accelerates to infinity along the $x$-axis. The ultimate speed of the point charge is .......

Three charges each of value $+q$ are placed at the corners of an isosceles triangle $ABC$ with sides $AB = AC = 2a$. The midpoints of $AB$ and $AC$ are $D$ and $E$ respectively. The work done in taking a charge $Q$ from $D$ to $E$ is (where $\varepsilon_0$ is the permittivity of free space):

The electric potential inside a conducting sphere:

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:

Two charges $3 \times 10^{-8} \; C$ and $-2 \times 10^{-8} \; C$ are located $15 \; cm$ apart. At what point on the line joining the two charges is the electric potential zero? Take the potential at infinity to be zero.