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

Lenz’s Law is the electromagnetic equalavent of Newton’s 3rd law paraphrased as “Every action has an equal and opposite reaction”.

Lenz’s Law: The current induced in a circuit due to a change in a magnetic field is directed to oppose the change in flux and to exert a mechanical force which opposes the motion.

What does this mean? It means that the induction of your spinning magnet will produce a counter-electromotive force or Back EMF which will cause the spinning magnet to slow down as it produces current.