1. The problem statement, all variables and given/known data A hollow metal sphere has 6 cm and 10 cm inner and outer radii, respectively. The surface charge density on the inside surface is -100 nC/m^2. The surface charge density on the exterior surface is + 100 nC/m^2 . What is the strength of the electric field at point 4 cm from the center? What is the strength of the electric field at point 8 cm from the center? 2. Relevant equations Inner Surface Charge = n = Q/A E = K*q/r^2 3. The attempt at a solution Well I got the 1st one right: Convert all the nC and cm to C and M. E (at .04 m) = = [K * q]/r^2 = [K * nA]/r^2 = [K * n(4(pi)R^2)]/r^2 (note R = inner sphere radius and r = 4 cm from center) For the 2nd part I'm unsure. How do I found out the charge on the part of the sphere in between the hollow and exterior at 8 cm? Is it q = nA - nA_2? q = [1*10^-17 * 4pi(.1m)^2] - [-1*10^-17 * 4pi(.6m)^2] Then repeat previous problem with E (at .08m)?