This is my first time using this site so please excuse me if I missed any guidelines. 1. The problem statement, all variables and given/known data A plastic rod having a uniformly distributed charge Q=-25.6pC has been bent into a circular arc of radius R=3.71cm and central angle ∅=120°. With V=0 at infinity, what is the electric potential at P, the center of curvature of the rod? 2. Relevant equations V=∫dV=∫kdq/r 3. The attempt at a solution V=∫dV=∫kdq/r=(kλ)∫dΘ=(kλ)(2π/3), which is wrong. The issue that I'm having with this problem is that I don't understand why the integration is done the way that it is. The equation I'm given to solve it is V=∫kdq/r, which equals out to V=kq/r after the integration. I'm confused because this is just the same exact equation used to find V for point charges. Why are you not required to put the integral in terms of theta and integrate over the length of the arc? If the charge distribution were kept as a straight rod, then I would have to integrate over the entire distribution, but since its a circular arc that just goes out the window.