Question

In this exercise you will figure out the equipotential point/points(s)/line/surface in the xy plane where V = 0 for two point charges of charge q and -2q found respectively at (x,y,z) = (-1,0,0) and (x,y,z) = (1,0,0), and draw the result on Fig. ??.

(a) Given that V is a scalar, equipotentials generally form surfaces in three di- mensions. This contrasts with the electric field, where we found only one position where it was zero for a pair of point charges. In the x-y plane for the two charges shown, do we expect a point, two points or a line where V = 0?

(b) Make a guess where the potential should be zero. Should it be zero closer to the smaller or larger charge? Why?

(c) Assign a label (x,y) to a general point in the x-y plane

Answer 1

a) at x=-2l potential is zero, so it's a point in xy plane

b)it should be closer to the smaller charge (2q) because potential is directly proportional to the amount of charge and in versely proportional to the distance, thus for same q/r ratio , for smaller charge r should be small