1. The problem statement, all variables and given/known data A solid, insulating sphere of radius a has a uniform charge density of ρ and a total charge of Q. Concentric with this sphere is an uncharged, conducting hollow sphere whose inner and outer radii are b and c, as shown. A). Find the magnitude of the electric field in the following regions: r < a (Use the following as necessary: ρ, ε0, and r.) a < r < b b < r < c r > c B). Determine the induced charge per unit area on the inner and outer surfaces of the hollow sphere. 2. Relevant equations Gauss's law for electric field (?): E∫dA = (q in) / (ε0) E = ke q / r2 E = 0 inside a CONDUCTOR q = σdA (surface area?) q = ρdV (volume? ) 3. The attempt at a solution I'm just concerned about the first part r< a and hopefully I will understand the rest This is just really tough for me... so many things I need to look out for and it is really confusing. It is confusing when thinking about dimensions as the uniform charge is concerned with volume ( q = ρdV) yet I thought Gauss's Law ( flux = E ∫ dA ) was just concerned with 2D surface area only. Or am I missing something? Also I am not sure how the inner sphere, being an insulator, has any affect on the electric field. So... for r < a, the electric field is not 0 and so E ∫ dA = q in / ε0 E (4πr2) = q in / ε0 E = q in / (4πr2ε0) which turns out wrong for r < a. It is still wrong even when I substitute q in as pV.