Inside a charged hollow sphere,at any point the electric field $(E)$ and potential $(V)$ are

'Inside a conductor,the electrostatic field is zero'. Explain.

Two isolated metallic spheres of radii $R$ and $2R$ are charged such that both have the same charge density $\sigma$. The spheres are then connected by a thin conducting wire. If the new charge density of the larger sphere is $\sigma_1$. The ratio $\sigma_1$ to $\sigma$ is

Assertion : In a cavity within a conductor,the electric field is zero.
Reason : Charges in a conductor reside only at its surface.

Two charged spherical conductors of radii $R_1$ and $R_2$ are connected by a wire. The ratio of surface charge densities of the spheres $\sigma_1/\sigma_2$ will be

Two metallic spheres of radii $a$ and $b$ are placed far away from each other and are connected by a thin conducting wire. The total charge on them is $Q$. Calculate the potential of each sphere.