I was watching this video of veritasium today and was wondering why the aluminum plate doesn't oscillate when there is a changing magnetic flux. When the flux is increasing, the induced magnetic field (by the induced current) is against the magnetic field of the coil and this acts like 2 north or south poles facing each other, and hence they repel. But if the flux was decreasing, the induced magnetic field would be in the direction of the larger or main magnetic field. In this case, shouldn't they attract each other? acting like a north and a south pole? Since the drive current is sinusoidal, it should have equal amounts of each
I understand that as the plate gets closer to the main coil, the change in flux increases and there would be more repulsion than attraction on average, but the plate should still be oscillating right?.
Is it because the plate doesn't have enough time to respond?
Thanks for your replies