Q: There is a sphere with uniform volume charge density (non-conducting of course, duh!) A spherical cavity has been made inside it. Find the net electric field at the centre of the CAVITY.

Case I:

i.e. The centres of the sphere and cavity coincide.

(Hint: Symmetry – PRESENT)

Case II:

i.e. the cavity is to one side of the sphere.

(Hint: Symmetry – ABSENT)

wat ?