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Electromagnetism confuses me

  1. Jun 7, 2006 #1
    I'm very confused

    Electromagnetism confuses me.

    In a circuit the movement of electric charges creates a magnetic force.
    (the type of magnetic force that is associated with magnets)
    Why does the movement of electric charges produce a magnetic force?

    The combination of a electric field and a magnetic field is often referred to as the electromagnetic field. Electromagnetic radiation is often associated with light (gamma waves. microwaves, infrared ..etc) . How is the repulsion force (magnetic force) generated by a circuit related to electromagnetic radiation?

    I'm trying to find a theoretical explanation that clarifies things in my head.

    thanks for reading
  2. jcsd
  3. Jun 7, 2006 #2


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    Hi, Deadly;
    First off, welcome to PF. Despite the meanderings of the likes of me, this is the best site that you could ever hope for when it comes to technology and science in general. I'm probably the least educated person here, but I think that I can give you a start on your question.
    To start with, you can't really think of electromagnetism as being a combination of electricity and magnetism. They're different faces of the same thing. Electromagnetism is the force communicated by photons. It can manifest itself in many ways, from the deflection of a compass to the fact that you can see the world around you.
    The 'repulsion' force that you mentioned only occurs when two similar poles of a magnet (or EM field) come together. Opposites attract; like repels. You can therefore think of an EM field the same way that you would think of a permanent magnet. At this point, I'm going to turn the response over to someone more qualified... and more sober...:redface:
  4. Jun 7, 2006 #3


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    There are probably 2 answers to be given:
    In order to understand the "how" part, you should try to read an intro book on classical electromagnetism. There, the equations are explained of how you have to calculate a magnetic field that is generated by, say, the current of electrical charges in a wire, or the other aspects.

    As to the "why" part, in as much as this isn't answered by the "how" part, you won't find the explanation in any science book. "Why" (different from "how") is not answered by science. In science you just observe phenomena, and if you're lucky, you discover the equations that can describe these phenomena. But you never know *why* this is the way it is. Of course, up to a point, the "why" and "how" questions are related:

    why does an apple fall down ?
    "because of" gravity: because the pull of gravity that exerts a force of GMm/r^2 on the apple...

    But we have written "GMm/r^2" exactly because we see apples fall down, and planets turn and so on, and this was the right equation that could fit all these observations !

    So, fundamentally, we don't know "why" apples fall down, why there is light and why current generates a magnetic field. We have the equations that tell us this, but we wrote down these equations because we saw things happening that way ...
    and sometimes, because we wanted to write down nice equations, which looked like others we already had, and guessed it right. For instance, after having observed apples fall down, we guessed (correctly) that the SAME equation also worked for oranges falling down.
  5. Jun 8, 2006 #4


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    Yeah... that's one of the guys that I was referring to.
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