At the Brilliant office, we have a new toy that mysteriously arrived. It's a small black circular platform that comes with a tiny metal top. Our CTO Sam gave it a spin this morning, and here it is, at lunch time, still going:
(click for video)
It looks like it has a battery inside, so we presume that there's some sort of electromagnet. Well, this got me thinking about the impossibility of perpetual motion. On a high level, you could say that the energy that is keeping the top from succumbing to friction and falling over is being supplied by the battery.
I presume that electromagnetism is somehow responsible. If the magnetic field supplied by an electromagnet can keep it going, could you do the same thing with the field created by magnetized iron? In other words, as iron gets magnetized, does potential energy go into it that can come out slowly over time in the form of (for instance) stabilizing this top, slowly demagnetizing the iron over time?
But this doesn't sit right with me. An unchanging field (magnetic or otherwise) should never be supplying energy, right? As I understand, it only defines which states are high energy or low energy, the path between the states should be irrelevant. So what must really be happening is that the electromagnet is creating a changing magnetic field, which is what is keeping this thing going. But then, by what mechanism might it be working? Perhaps it's like a motor, and the top isn't uniform metal.