Eli5: why cant we use magnets to make an infinitely spinning thing to get infinite energy

Question

-english is not my first language-

Edit: alot of people think im referring to motors or generators or some sorts. But I mean something like this:

https://i.ytimg.com/vi/BSdSDfOWbNs/maxresdefault.jpg

I know its probably fake and not possible but I want to know why and how

In: 0

Answer 1

Magnets have a feature called cogging torque. It’s helpful to imagine magnets arranged in a way where you would think they could spin infinitely as like gears. There is a point where the magnets fall into a place where an equal amount of force if needed to pull or pull them in either direction to get past the “next tooth in the gear” to continue moving.

Captain Disillusion has an excellent video that provide a visual explanation of this: https://youtu.be/sT_bTnkwLuE