1. The problem statement, all variables and given/known data A sphere of radius R has volume charge density = B/r for r < R, where B is a constant and = 0 for r > R. (a) Find the total charge on the sphere. (b) Find the expressions for the electric field inside and outside the charge distribution. (c) Sketch the magnitude of the electric field as a function of the distance r from the sphere’s center 2. Relevant equations 3. The attempt at a solution I got the charge by integrating (4 pi B r dr) over 0 to R as (2 pi B [R^2]). For the part b, that's where I am confused.The solution that I have and the answer that I got are different as the approach is different. What I have done is: Q/(Q inside) = (4/3 pi R^3)/(4/3 pi r^3). Substituting Q in this equation from above and using the Gauss' law, I got E = (B r)/(2 R ε0) But in the solution: For r<R, they have just simply substituted Qinside = (2 pi B [r^2]) and got E = B/(2 ε0) For r>R, they have just simply substituted Qinside = (2 pi B [R^2]) and got E = [B(R^2)]/[2 (r^2) ε0] What here I am confused is 2 things. 1. How does the total charge become the inside charge as the solution says. 2. Notice the Q inside for r<R, it has small r but r>R has big R.