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Electromagnetic Induction Question

  1. Oct 13, 2011 #1
    Can someone please tell me why the magnetic field makes the electrons flow round the coil in a generator? Does the force of the magnetic field have to go in the same direction as the coil?
  2. jcsd
  3. Oct 13, 2011 #2


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    Staff: Mentor

    A voltage is induced in the coil, and it is this voltage which pushes electrons around the coil and through the external circuit. In order to induce a voltage in a conductor, the conductor must cut through or cross the magnetic flux lines.

    So if you are wearing a gold watchband, running cross-country from north to south will not induce a voltage in your watchband because you are moving along a magnetic line of the earth (these imaginary lines are drawn around the earth from the North Pole to the South Pole). But if you run east-west you are cutting across the earth's magnetic lines and causing a voltage to be induced in your watchband (providing you orientate it to best effect).

    Even so, the voltage is too small for you to measure.
    Last edited: Oct 13, 2011
  4. Oct 13, 2011 #3
    Why does cutting the lines of the magnetic field cause electrons in the copper wire to be deflected in the right direction? When the wire goes through the magnet it is at a right angle to the magnetic field-

    2011-10-13 18-11-14.984.jpg

    See what I mean? So how do the electrons get pushed up vertically by a magnetic field that seems to be horizontal?
    Last edited: Oct 13, 2011
  5. Oct 13, 2011 #4
    I haven't got an answer yet, can someone please reply with an answer?
  6. Oct 13, 2011 #5


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    It is a good, but hard question. Try to google it, or maybe wikipedia got an answer. What I have learned, and it might not be correct, is that electromagnetism will affect the free electrons in a conductor when applying a force as when moving the conductor through the electromagnetic field. Free electrons in the conductor will gather on one side of the wire. When you load this wire the elerctrons can flow back to the other end with lack of electrons. But as long the wire is moving through the electromagnetic field the electron flow will continue.

    I hope someone have a better answer.

  7. Oct 13, 2011 #6


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    Staff: Mentor

    For that answer, you'll have to ask the Creator. :smile:

    That gives maximum induced voltage. At other angles, you still get induced voltage, but of lesser magnitude.

    Direction of movement, direction of magnetic lines, and the induced current are all vector quantities and are all perpendicular to each other: an x-y-z 3-dimensional space.
  8. Oct 13, 2011 #7
    Originally Posted by Eisen
    Originally Posted by NascentOxygen
    Ask the creator, you mean God? Come on, surely one of the mere mortals on here has the answer? :biggrin: But seriously though, isn't there a theory to explain this?
    Last edited: Oct 13, 2011
  9. Oct 13, 2011 #8


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    You seem to be asking about the origin of the interaction of electric and magnetic fields. It turns out that they are one and the same, depending on your relativistic frame of reference. I would look into electromagnetism and relativity. Try here: http://physics.weber.edu/schroeder/mrr/MRRtalk.html
  10. Oct 13, 2011 #9


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    Are you looking for something like this? http://en.wikipedia.org/wiki/Lorentz_force

    The lorentz force describes the force on a charged particle by electromagnetic fields. A charged particle feels a force in a direction that is perpendicular to a magnetic field line. I would hit up the above article and browse around to learn more if you are interested.
  11. Oct 13, 2011 #10
    Thanks for your replies, I am continuing to investigate electromagnetic induction.
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