First time poster here! EDIT: SOLVED!! Thanks, I figured out from the related links at the bottom of the page. >_>b 1. The problem statement, all variables and given/known data Find the electric field inside a sphere which carries a charge density proportional to the distance from the origin, [tex]\rho[/tex] = kr, for some constant k. 2. Relevant equations [tex]\oint E.da[/tex] [tex]a = 4 \pi r^2/3[/tex] [tex]da = 4 \pi r^2[/tex] [tex]\rho = kr[/tex] [tex]E = q/(r^2 4 \pi \epsilon _0)[/tex] Where q = charge inside 3. The attempt at a solution [tex]\oint E \bullet da = \int q/(r^2 4 \pi \epsilon _0) \bullet 4 \pi r^2[/tex] The 4 pi r^2 terms cancel, leaving on the right [tex]q/ \epsilon_0[/tex] Substitute rho into the eqn. as to integrate all dimensions of the sphere [tex] \int \rho d \tau / \epsilon_0[/tex] Here's where I get stuck, I know that [tex] \rho = kr [/tex] What do I do with [tex]d \tau[/tex]? I'd imagine that it'd be easiest to do in spherical coordinates, so do I just add dr, dtheta, drho? Also... How do I put a dot into this LaTex thing? Thank you!