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I What actually makes a magnetic field?

  1. May 29, 2018 #1
    I have tried looking this question up and I hope I am posting this question in the correct spot. I have read a little about photon clouds which surround electrons in a magnet but since I see myself as a very visual learner I think I am trying to think about this question as if something is actually transferred between two magnets. Is there something physical that creates a magnetic field? If so what is it and what is being transferred between two magnetic poles to create a field? Or am I completely on the wrong track?
     
  2. jcsd
  3. May 29, 2018 #2

    Orodruin

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    The magnetic (or more accurately, the electromagnetic) field is not ”made” of anything. It is a quantum gauge field and that is about as far as physics goes. It is not the aim to ascribe it to some substance or building blocks.

    Particles (photons in the case of the EM field) and classical fields are described by different states of the quantum field.

    What do you mean by ”physical”? In most senses that word is used in physics, the EM field itself is physical.
     
  4. May 29, 2018 #3

    Drakkith

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    Forget you ever read that. It's a watered down explanation of virtual particles, which require a substantial background in quantum physics (and the math underlying it) to understand.

    I wouldn't try to think of it that way.

    A field is a way of particular representing something using math. For example, we could measure the wind velocity at ten feet above the ground at many points across a wide area. This wind velocity field could then be represented by a 2D grid or a table of values, much like how they show the weather on weather channels.

    The magnetic field is one part of the electromagnetic field and contains the values of the magnetic field vectors for each point in space. These vectors represent the direction and magnitude of the magnetic forces a charged particle would feel.

    And that's pretty much it. The magnetic field is just the way we model the forces a charged particle would feel. There's nothing else underlying the electromagnetic field that you could use to explain it. You could try to invoke quantum physics, but that's not going to change the explanation drastically at this level since we aren't worried about the mathematical details in this thread.

    I'd like to stress again that the magnetic field (and the EM field as a whole) is a way of modeling or representing how charged particles interact. It's something that we created to help us explain the world and there may be alternative ways of representing these interactions without using fields. That wouldn't change anything about the underlying physical laws of the universe, it would only change how we explain and represent them.
     
  5. May 29, 2018 #4

    atyy

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    Either a current or a changing electric field creates a magnetic field, in the same way that an electric charge creates an electric field.
     
  6. May 30, 2018 #5

    Orodruin

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    While this is rather standard to tell entry level students, I do not like it much as it suggests that there magnetic field is not there if there are no currents or that there are several magnetic fields if there are more than one current. There is only one magnetic field and it is sourced by currents. Then Maxwell’s equations are linear so that you can separate the contributions of different currents to it and add them up without breaking anything.
     
  7. May 30, 2018 #6

    sophiecentaur

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    I can't think of a suitable alternative way into this stuff if you want to reject the idea of superposition. It works very well and there doesn't seem, to me, that there is any reason not to accept it. Where would you start with students who have not progressed past concrete concepts? For instance, the OP asks for "visual" explanation of the phenomenon. Are we to say that, without some advance Maths (at the very least), Magnetic Fields are just 'too hard?
    Looking back, from a slightly better informed standpoint, that point of view could be argued but it could be viewed as too elitist and unlikely to encourage entry into Physics.
     
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