$A$ and $C$ are concentric conducting spherical shells of radius $a$ and $c$ respectively. $A$ is surrounded by a concentric dielectric of inner radius $a$, outer radius $b$ and dielectric constant $k$. If sphere $A$ is given a charge $Q$, the potential at the outer surface of the dielectric is.
$\frac{Q}{{4\pi {\varepsilon _0}kb}}$
$\frac{Q}{{4\pi {\varepsilon _0}}}\left( {\frac{1}{a} + \frac{1}{{k(b - a)}}} \right)$
$\frac{Q}{{4\pi {\varepsilon _0}b}}$
None of these
In the following figure two parallel metallic plates are maintained at different potential. If an electron is released midway between the plates, it will move
Two spheres $A$ and $B$ of radius $a$ and $b$ respectively are at same electric potential. The ratio of the surface charge densities of $A$ and $B$ is
Figure shows a solid hemisphere with a charge of $5\ nC$ distributed uniformly through its volume. The hemisphere lies on a plane and point $P$ is located on this plane, along a radial line from the centre of curvature at distance $15\ cm$. The electric potential at point $P$ due to the hemisphere, is .....$V$
The electric potential inside a conducting sphere
A small conducting sphere of radius $r$ is lying concentrically inside a bigger hollow conducting sphere of radius $R.$ The bigger and smaller spheres are charged with $Q$ and $q (Q > q)$ and are insulated from each other. The potential difference between the spheres will be