advantages:
- can be leveraged in a macroscopic study of the Einstein de Haas effect (perform this experiment using four coils on a toroid and energize them in quadrature) and place/hang a ferromagnetic ring over it. As Feynman demonstrated with a three-phase version of the same, what he actually demonstrated was the effect of this eddy current interacting with a ring suspended over the device (a three phase toroidal transformer) and showed the effect to his students at that time. Here is a similar experiment using a similar three-phase toroidal transformer. Note: Nikola Tesla first discovered this effect in his egg of columbus apparatus. He used a four coil toroid and energized it mechanically in quadrature with two phase AC. Best results were around 40 cps.