$A$ point charge is kept at the centre of a metallic insulated spherical shell. Then:

Two charged conducting spheres of radii $a$ and $b$ are connected to each other by a wire. What is the ratio of electric fields at the surfaces of the two spheres? Use the result obtained to explain why charge density on the sharp and pointed ends of a conductor is higher than on its flatter portions.

Show that electrostatic potential is constant throughout the volume of the conductor and has the same value (as inside) on its surface.

Two metal spheres have their radii in the ratio of $4:7$. They are put in contact and a charge $8.8 \times 10^{-7} \text{ C}$ is given to the system. Then they are separated so that each can exert no influence on the other. The potential due to the smaller sphere at $60 \text{ m}$ from it in Volt is

$A$ charge $q$ is placed at $O$ in the cavity of a spherical uncharged conductor. Point $S$ is outside the conductor. If the charge is displaced from $O$ towards $S$ while still remaining within the cavity,then:

$A$ solid conducting sphere of radius $a$ has a net positive charge $2Q$. $A$ conducting spherical shell of inner radius $b$ and outer radius $c$ is concentric with the solid sphere and has a net charge $-Q$. The surface charge density on the inner and outer surfaces of the spherical shell will be