Can a metal be used as a medium for dielectric

If electric potential of the inner sphere is $10\, volt$ and that of the outer shell is $50\, volt$ then potential at common centre is :-......$V$

A charge $q$ is distributed uniformly on the surface of a sphere of radius $R$. It is covered by a concentric hollow conducting sphere of radius $2 R$. Charge on the outer suiface of the hollow sphere will be, if it is earthed

Two isolated metallic solid spheres of radii $R$ and $2 R$ are charged such that both have same charge density $\sigma$. The spheres are then connected by a thin conducting wire. If the new charge density of the bigger sphere is $\sigma^{\prime}$. The ratio $\frac{\sigma^{\prime}}{\sigma}$ is

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.

Two metallic spheres of radii $1\,cm$ and $2\,cm$ are given charges ${10^{ - 2}}\,C$ and $5 \times {10^{ - 2}}\,C$ respectively. If they are connected by a conducting wire, the final charge on the smaller sphere is