1. The problem statement, all variables and given/known data A thin plastic rod 15 cm long carries 4.2 nC distributed uniformly over its length. (a) If the rod is bent into a ring, find the potential at its center. (b) If the rod is bent into a semicircle, find the potential at the center (i.e., at the center of the circle of which the semicircle is part). 2. Relevant equations V = KQ/r potential at a point. 3. The attempt at a solution when bending the rod, how to find the distance r.