If volume charge density is $\rho$,then what will be the charge on $\Delta V$ volume?

The surface charge density $\sigma$ on a charged conducting sphere of radius $R$ in terms of the electric field intensity $E$ at a distance $r$ $(r > R)$ in free space is (where $\varepsilon_{0}$ is the permittivity of free space):

If a solid and a hollow conducting sphere have the same radius, then:

If on two concentric hollow spheres of radii $r$ and $R$ $(R > r)$,the total charge $Q$ is distributed such that their surface charge densities are equal,then the potential at their common centre is:

$A$ spherical conducting shell of inner radius $r_1$ and outer radius $r_2$ has a net charge $Q$. $A$ point charge $-q$ is placed at the center of the shell. Determine the surface charge density on the inner and outer surfaces of the shell.

What are linear,surface and volume distribution of charge?