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Why is a current induced in a conductor placed in a changing m.field ?

  1. Dec 16, 2013 #1
    the title says it all , why does a changing magnetic field* or a moving conductor * induce a current ?
    i know the how , i know how it works ,i know that a changing magnetic field creates a changing electric field , but i want to understand how this works on the electronic level , what is the real reason behind this induction ?
     
  2. jcsd
  3. Dec 16, 2013 #2
    Look up Lorentz force. It covers this.

    Claude
     
  4. Dec 16, 2013 #3
    In simple terms, the Lorentz force. Just like a free moving electron in a magnetic field feels a force, so does a conducting wire (made up of many electrons). Leading on from the Lorentz force, special relativity demands that electricity and magnetism are one in the same, just different manifestations of the same force. Also induction helps conserve energy in a system. If a static magnetic field produced currents in a stationary wire it would violate energy conservation laws.
     
  5. Dec 16, 2013 #4
    If I may ask the 1st poster a question, (s)he said (s)he knows the answer to the how question, but not the why question.

    1st: What's the difference?

    2nd: If there is a difference, is the why question answerable?
     
  6. Dec 16, 2013 #5
    I think the OP KNOWS what happens when you put a wire in a mag field, he/ she just wants a deeper descripton of what's happening on a smaller scale
     
  7. Dec 17, 2013 #6
    i know what happens and i know how to calculate the emf produced , its just what i really want to know is why or even how that happens at the atomic levels , my textbook says that the field affects free electrons in the conductor , but how does the field affect them ?
     
  8. Dec 17, 2013 #7
    Yes the magnetic field interacts with electrons. Any charged (positive or negative) particle interacts with magnetic fields. If we look at this from a QFT perspective the magnetic field is made up of (not sure the correct wording here) virtual photons that mediate electromagnetic force. Photon/ electron interaction is depicted by feynman diagrams. I dont think the explanation could get any deeper. You could keep asking why or how but there may not be an answer to that...
     
  9. Dec 17, 2013 #8
    so i should basically take it as my teacher says , conductors oppose the change in magnetic field by creating their own magnetic fields . thats it right ?
     
  10. Dec 17, 2013 #9
    The induced current creates an opposing magnetic field in a conducting loop. Like I said in my first post there are some subtle consequences of all this that will only be appreciated through further study of maxwell's equations, namely invariance, conservation of energy etc. QFT would be the next step in a deeper more fundamental understanding of this phenomenon.

    Cris
     
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