1. The problem statement, all variables and given/known data A hollow insulating sphere with an inner radius of 6.58 cm and outer radius of 11.7 cm has a uniform charge density of 79.9 μC/m3 distributed throughout the volume between. If we want to use Gauss' Law to find the electric field at r = 17.2 cm, what "charge enclosed" should we use? 2. Relevant equations RHO = Q/V a = .0658 m b = .1170 m r = .1720 m therefore r > b > a 3. The attempt at a solution i kno RHO = Q/V i just don't kno what V to use i've used v = 4/3(pi)(.1720^3) i've used v = (4/3)(pi)(.1720^3 - .1170^3) think i've used every combination of r i kno i'm overlooking something incredibly simple blah!