If we put the bar magnet on the carrousel, it will rotate around the center. If the magnetometer is located at the center, it will feel the magnetic field of the magnet. This interaction represents the spin-dipolar contribution.
For the analogy of the orbital contribution, we simply replace the magnet with the electrically charged ball.
The fermi contact contribution can be simulated if the kid picks up both items and runs towards the center where the magnetometer is.