electrically charge ball is kept at center of the carousel along with magnetometer to observe MF. Now the child (first case with and second case withoug BAR magnet) is made to site on the horse. MF is observed at magneto meter.
Bar magnet at center and charged ball with child.
The carousel starts rotating. Child with charged ball is having fun. As the speed of carousel increased, child’s horse is moving away from the electrically bar magnet. Distance between ball and bar magnet, R, is increased. Ring for the ring current got slightly bigger so the contribution to hyperfine field will decrease.