Gauss' Law - Sphere with spherical cavity - Please help 1. The problem statement, all variables and given/known data A sphere of radius 2a is made of nonconducting material that has a uniform volume charge density . (Assume that the material does not affect the electric field.) A spherical cavity of radius a is now removed from the sphere, as shown in Figure P19.62. Show that the electric field within the cavity is uniform and is given by Ex = 0 and Ey = Pa/3Eo. (Hint: The field within the cavity is the superposition of the field due to the original uncut sphere, plus the field due to a sphere the size of the cavity with a uniform negative charge density -.) http://greenlanternbattery.googlepages.com/p19-62.gif 2. Relevant equations P= Q/V 3. The attempt at a solution Esphere=Q/Eo I'm not really sure if the Esphere is right, and I'm not sure where to go next if it is. In my notes from the prof, it says "for each point P in the cavity need to consider the contribution to the E field from the positive charge distribution (let the vector be r+) and from the negative charge distribution (r-)." I am not really sure what this means though.