Figure 7.

Differential movements of field centroids caused by decreasing the card separation by 25°. (A) To a first approximation, the pattern of field centroid movements caused by moving the two cards closer together is similar to but in the opposite direction of the movements caused by moving the cards apart. The magnitude of the effect is, however, weaker than in the case of the apart manipulation. (B) The curves on the graphs are sine functions fitted by eye. (1) The variation of the angular component of the displacement vectors is clear and has the same pattern as for the together manipulation; field centroids near either card tend to rotate with that card, whereas fields in the sectors between the cards tend not to rotate. (2) An overall tendency of fields in the sectors between the two cards to move relative to the cylinder center is visible but weaker than was the case for the apart manipulation. This effect is most evident from the preponderance of positive radial displacement components in the small arc between the cards.