A charge of 3.45 µC is uniformly distributed on a ring of radius 9.0 cm. Find the electric field strength on the axis at the following locations.
(a) 1.2 cm from the center of the ring
(b) 3.1 cm from the center of the ring
(c) 4.0 m from the center of the ring
(d) Find the field strength at 4.0 m using the approximation that the ring is a point charge at the origin.
(e) Compare your results for parts (c) and (d) by finding the ratio of the approximation to the exact result.