If the electric potential of the inner metal sphere of radius $a$ is $10 \text{ V}$ and that of the outer spherical shell of radius $b$ is $5 \text{ V}$,then the potential at the centre will be ...... $\text{V}$.

Two spherical conductors of radii $4 \ cm$ and $5 \ cm$ are charged to the same potential. If $\sigma_1$ and $\sigma_2$ are the respective values of the surface charge density on the two conductors,then the ratio $\sigma_1 : \sigma_2$ is

Four charges,each of value $Q = \frac{10}{3} \times 10^{-9} \ C$,are placed at the four corners of a square of side $a = 8 \ cm$. What is the electric potential at the center of the square?

When a proton is accelerated through a potential difference of $1 \, V$, its kinetic energy is .......... $eV$.

Two equal point charges are fixed at $x = -a$ and $x = +a$ on the $x$-axis. Another point charge $Q$ is placed at the origin. The change in the electrical potential energy of $Q$,when it is displaced by a small distance $x$ along the $x$-axis,is approximately proportional to

$A$ conducting sphere of radius $R$ is given a charge $Q$. The electric potential and the electric field at the centre of the sphere respectively are