Charge q1 = – 7.2 x 10-9 C is at the origin, and charge q2 = 2.5 x 10-9 C is on the y axis at y = 0.50 m. Take the electric potential to be zero far from both charges.

(a) Plot the intersection of the V = 5.0 V equipotential surface with the xy plane. It encloses one of the charges.

(b) There are two equipotential surfaces corresponding to V = 3.0 V. One encloses one of the charges and the other encloses both charges. Plot their intersections with the xy plane.

(c) Find the value of the potential for which the pattern of the electric potential switches from one equipotential surface to two.