A circular plastic rod of radius R = 1.20 m has a positive charge = Q = 3.00×10-6 C uniformly distributed along one-quarter of its circumference and a negative charge of -4Q uniformly distributed along the rest of the circumference (see the figure). (At infinity V is zero).
What is the electric potential at the center C of the circle?
What is the electric potential at point P, which is on the central axis of the circle at a distance z = 0.792 m from the center?