1. The problem statement, all variables and given/known data the electric potential of some configuration of charge is given by the expression: V(r)= (Ae^(-pr))/(r) where A and p are constants. Find the E-field E(r), the charge density rho(r) and total charge Q. The answer for rho is given in book as: epsilon-not * A * ((1/r)4* pi* dirac delta^3 (r) - p^(2) e^(-p*r)) (The stuff inside parentheses is all divided by r 2. Relevant equations -del V= E; del dot E = rho/epsilon-not ; 3. The attempt at a solution I the took gradient of V using sperical coordinates using the formula -del V= E to obtain E. Then I used the formula del dot E = rho/epsilon-not to find rho. I am not getting the same rho as in the book. I dont understand why the dirac delta function is in the answer. Do you have to perform an integration or am I taking a wrong apprach all together?