1. A solid sphere of radius a = 12.8 cm is concentric with a spherical conducting shell of inner radius b = 37.1 cm and outer radius c = 39.1 cm. The sphere has a net uniform charge q1 = 9.00×10-6 C. The shell has a net charge q2 = -q1. Find expressions for the electric field, as a function of the radius r, between the sphere and the shell (a < r < b). Evaluate for r = 25.0 cm. 2. ∫E.dA = Q/ε0 ρ = Q/Volume 3. OK, so I have the charge density of the insulting sphere, which I'm calling ρ. My Gaussian surface is a sphere, so it's area in this case would be 4∏(0.25m)^2 I know how to find the electric field inside of the insulating sphere, but not between the insulating sphere and the conducting shell, which is what this problem is asking for. I tried ignoring the conducting shell and just using the equation: E = (ρa^2)/(3ε0r^2) It's telling me that the answer is wrong. What am I doing wrong? I assume it has something to do with the charge on the inner surface of the conducting shell, but I don't know what to do with that.