A metal ring is dropped into a localized region of constant magnetic field, as indicated in Figure 23-36. The magnetic field is zero above and below the region where it is finite.

(a) For each of the three indicated locations 11, 2, and 32, is the magnetic force exerted on the ring upward, downward, or zero?

(b) Choose the best explanation from among the following:

I. Upward at 1 to oppose entering the field; zero at 2 because the field is uniform; downward at 3 to help leaving the field.

II. Upward at 1 to oppose entering the field; upward at 2 where the field is strongest; upward at 3 to oppose leaving the field.

III. Upward at 1 to oppose entering the field; zero at 2 because the field is uniform; upward at 3 to oppose leaving the field.