1. The problem statement, all variables and given/known data Insulator has a 3 cm radius and is a sphere. It has a total charge of -4.2 uC. I need to find the charge density of the insulator. 2. Relevant equations sigma = total charge / volume.... I think? 3. The attempt at a solution After using the above equation, I got -3.714E-8 C/m I am just not sure if this is the correct charge density for the insulator. I know that for conductors, I think the equation would be charge/area, but I think since an insulator contains the charge throughout the sphere and not just on the surface, you'd have to use volume correct? I am correct in my answer and thinking?