Conservation of energy and magnets

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Discussion Overview

The discussion revolves around the conservation of energy in relation to magnets, particularly focusing on the behavior of a precessing magnet and its interaction with magnetic fields. Participants explore concepts of magnetic potential energy, electromagnetic radiation, and the conditions under which light is emitted by magnets.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant suggests that a precessing magnet sheds light as it slows down, raising questions about conservation of energy.
  • Another participant clarifies that when a magnet is aligned in its magnetic field, the forces acting on it are symmetric and cancel out, resulting in no net force or acceleration, and thus no electromagnetic radiation.
  • Some participants discuss the idea that a static magnet does not produce a change in flux, leading to the conclusion that it does not emit light.
  • There is a suggestion that while a magnet may not emit light in a classical scenario, the transmission of force could be associated with light, indicating a potential link to electromagnetic phenomena.
  • One participant realizes that light is only emitted when there is a change in the magnetic field, such as in induction, which they find clarifying.

Areas of Agreement / Disagreement

Participants express various viewpoints on the emission of light by magnets and the conditions under which this occurs. There is no consensus on the necessity or mechanism of light emission in relation to static versus dynamic magnetic fields.

Contextual Notes

Participants reference classical mechanics and electromagnetic theory, but the discussion includes uncertainty regarding the transition between classical and quantum perspectives on light emission and magnetic interactions.

Who May Find This Useful

This discussion may be of interest to those exploring the principles of magnetism, electromagnetic theory, and the conservation of energy in physical systems.

nhmllr
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Things with a magnetic field constantly shed light. This is why a precessing magnet will slow down until it stands straight up, giving it the lowest potential energy. But if the magnet is standing straight up, it has no way to have less potential energy, but I would think that it would continue to have a magnetic pull, which would necessitate it the keep shedding photons/energy. But then what about the conservation of energy?

Thanks
 
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If the magnet is aligned in it's magnetic field ("straight up" in your reference frame) then there is a "pull" yes, in that there are forces on it. But the forces are symmetric, they cancel out; there is no net force on (and thus no acceleration of) the magnet. A static (non-moving) magnet does not produce a change in flux, so there is no electromagnetic radiation (i.e. no light).
 
Pythagorean said:
If the magnet is aligned in it's magnetic field ("straight up" in your reference frame) then there is a "pull" yes, in that there are forces on it. But the forces are symmetric, they cancel out; there is no net force on (and thus no acceleration of) the magnet. A static (non-moving) magnet does not produce a change in flux, so there is no electromagnetic radiation (i.e. no light).

So... The magnet is emitting and absorbing photons equally? Makes sense.
 
nhmllr said:
So... The magnet is emitting and absorbing photons equally? Makes sense.

I'm not quite sure there's any argument for emitting in the first place; at least not in a classical scenario. The flux pertains to magnetic field lines, not electromagnetic radiation.
 
Pythagorean said:
I'm not quite sure there's any argument for emitting in the first place; at least not in a classical scenario. The flux pertains to magnetic field lines, not electromagnetic radiation.

But the force has to be transmitted somehow, so light would seem like a way to do that.
Although if this is getting out of the range of classical mechanics then I'm content with the given answer.
 
Oh wait, light's only emitted when there's a CHANGE in the magnetic field? OHHHHHH OH OH OH I see. That actually makes sense (such as with induction)

Okay I think I get it.
 
yes :)
 

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