Consider the device shown in the figure below, Q being a load uniformly distributed over the non-conducting spherical shell of radius R; q and q 'are point charges, located in r and x from the center of the sphere. What are the forces acting on q, q 'and Q?
The image you find here:
https://uploaddeimagens.com.br/imagens/02Df3TM
So my question as follow, because the spherical shell is not conductive, it is necessary to consider the contributions of the charge q 'to q or we should only consider the interactions between Q and q and if there are forces acting on Q or if the electric field in the center is null and not there are forces at work in it. Please help!