# Spinning a top with assistance from a magnetic field

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.

Thoughts? Explanations?

Note by Dan Krol
4 years, 6 months ago

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What is especially confusing to me is that when you leave the top on the surface without spinning it, it is clearly laying on top of a magnetized surface, but it seems to be statically oriented (the top doesn't move around or point in different directions).

Staff - 4 years, 6 months ago

Question: Who is coughing in the background?

- 4 years ago

- 4 years ago

Wait your lawyer goes to work at an office? I thought he just writes one paper and then he's done. :O

- 4 years ago

Its a levitron toy. www.levitron.com/‎

- 4 years, 6 months ago

That got me all excited, but I tried it out and I sense no indication that it is supposed to levitate. The magnet is way too weak, I think it's a different sort of toy. The base looks different.

- 4 years, 6 months ago

Without referring to the site, though, how exactly does it work?

Staff - 4 years, 6 months ago