Statement : Inside a charged conducting spherical shell electric potential at any point is $\frac{\mathrm{Kq}}{\mathrm{R}}$ and at a point outside it, field is $\frac{\mathrm{Kq}}{{\mathrm{r}}^2}$ .Electric field inside the shell at any point is zero and outside it, field is $\frac{\mathrm{Kq}}{{\mathrm{r}}^2}$. Here K is $\frac{1}{4{\mathrm{\pi \epsilon }}_0}$R. is the radius of shell and r the distance from centre of shell. Two concentric spherical shells of radii R and 2R have charges Q and 2Q as shown in figure.