We must first place the magnetometer at the center of the carousel, to symbolize the nucleus experiencing the hyperfine field. Then the child will hold both the ball and the magnet in his hand, and will wander around on the carousel. Most of the time, he is on a horse, meaning the magnet and the ball are rotating around the magnetometer, giving both the dipolar and the orbital interaction. But sometimes, the child will be curious about the heart of the carousel, and will come closer to it. The bar and the ball will then mirror the effect of the contact interaction.