Many species of fish generate electric fields and use these fields to sense their surroundings. If another entity with a dielectric constant different from that of water comes near the fish, the electric field lines generated by the fish are altered, and sensory organs on the fish can detect these slight changes. The electric field of most of these fishes is that of a dipole. Figure Q18.10 shows lines of equal potential around such a fish as seen looking down on the top of the fish. Assume the fish?s head is positively charged.

(a) Sketch the electric field associated with these equipotential lines. (You may want to make a photocopy of the figure to proceed.) (b) If a sphere of metal (perhaps a metal fishing weight) were placed near the side of the fish, sketch how the field lines in the vicinity of the metal would change.?

Figure Q18.10