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I believe a magnetic field is caused by movement of charged particles.

But, what is it that is actually making the force between two magnets repel or attract to another? For repelling, I'm mentally visualizing a water balloon between two magnets. What is the water balloon composed of? Is it purely the "magnetic field"? If so, seems like more work needs to be done.

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I'm mentally visualizing a water balloon between two magnets. What is the water balloon composed of? Is it purely the "magnetic field"? If so, seems like more work needs to be done.

The interaction between electric (magnetic) fields from two sources is described by virtual photons. Virtual means, not existing in reality. So the real interaction between such fields is explained only in a statistical way and not in detail.

As long as the inner structure of these fields isn’t subject of interest, as long a detailed description is not possible. Why this is of an interest? Because, if one would think about an inner structure of such fields, there is no way not to think about some components or quanta. These quanta have to have some extent and energy content. Ergo electric and magnetic fields have to be finite. This would be in contradiction to the current perceptions.

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One model of a magnet (typically, ferromagnet) is the Ising model, which basically places an electron with spin at every atom in the structure of the magnet. Although the magnet is not charged overall, nor is it moving, there can be motion of the atoms (and electrons) that make up the magnet. In this model, the spin of the electron produces small magnetic moments which are aligned, and sum to a large magnetic moment.

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So permanent magnetic materials are termed ferromagnetic. It is a good question to ask what the nature of the force is between two magnets, but I believe the answer is: we don't know.

Take as a similar type of example: electric charges. We know that like electrical charges repel one another and unlike charges attract, and we have an equation which we can use to calculate the resultant force (Coulomb's law).

But as to why it is so that like charges repel and unlike charges attract, we can only say that the fields created by these charges interact in such a way as to make this true.

The same with magnets. The magnetic field surrounding magnets will interact in such a way as to make like poles repel and unlike poles attract.

Perhaps someone who is versed in QED can tell us if that theory shines any stronger light on this.

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  • $\begingroup$ " charges repel and unlike charges attract, we can only say that the fields created by these charges interact in such a way as to make this true." I agree this is the typical explanation but it still doesn't explain to me in a mechanistic sense of what is causing the observed effects: what thing is attracting/repelling the other thing? It is similar to the logic of my parents saying "because I said so" when young. $\endgroup$
    – Bob22
    Jul 31 '20 at 19:27
  • $\begingroup$ Sure. And that's why I wrote that ultimately we don't know. Even to use a QED explanation that virtual photons are exchanged only pushes the question to a different level. Unfortunately, there are just some things we don't have satisfactory explanations for. For example, one can say that gravity is due to the warping of space by mass, but that only leads to the question: why does mass warp space? As far as I know, we don't know. $\endgroup$
    – CGS
    Jul 31 '20 at 19:34
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The magnetic force can be understood as a relativistic effect on the electric force. It results from Lorentz transformation of the electrostatic force for a stationary charged particle.

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