I don't know if this is the correct section. It is not exactly a homework problem, but here it is: If I were given a circle of charge with radius r and were asked to find the electric field due to this circle of charge at the center of the circle, would it be valid to do the following: Since I know the radius of the circle of charge, could I imagine the circle of charge to be a line of charge, and the point in question be r away. That is, find the circumference of the circle, as if I were stretching out the circle into a straight line of length equal to the circumference of the circle. Then, I could calculate the electric field due to the line of charge at a distance equal to the radius of the circle. Is this valid to do? I am sure there would be an easier way to solve this problem, but just out of curiosity, would this work?