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Electromagnetic Field

  1. Jan 23, 2005 #1

    DB

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    Why is it that as a particle propagates through an electromagnetic field, the electric and magnetic forces are perpendicular to eachother? (through the straight line of the particles motion) What effect does this have on the particle's motion, wavelenght and frequency?

    Thanks
     
  2. jcsd
  3. Jan 24, 2005 #2
    The force on the particle is Lorentz's Force : F = qE + q(VxB). Are you asking for a demonstration of this?

    If you want a specific trajectory for the particle, you need to describe the EM field more specifically, as an EM field can be shaped to cause any trajectory you want.

    In classical physics, particles do not have a wavelength or frequency. (unless they have an oscillatory trajectory, of course.
     
  4. Jan 24, 2005 #3

    dextercioby

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    Let's discuss the very simple common case when an electrically charged particle is moving in the electromagnetic field created by other sources (not by the particle itself).Then the nonrelativistic force is the famous Lorentz force...The fields E and B are solutions of the Maxwell equations and it can be shown that they are perpendicular one to another...That's all.

    Things could become really complicated if the particle is relativistic...Or if the field is quantum or if the particle is quantum...

    Daniel.
     
  5. Jan 24, 2005 #4

    DB

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    So their is no specific reason why an E and B field are perpidicular to eachother?
     
  6. Jan 24, 2005 #5

    dextercioby

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    I just told you that there is:if both E & B are solutions to the field equations,then in the EM field they are perpendicular one to another and moreover,it can be shown to be BOTH perpendicular on the direction the field (par éxample a EM wave) is propagating...

    Daniel.
     
  7. Jan 24, 2005 #6
    The simple and most truthful answer is - nobody knows. That's why there is a law regarding it. Its taken as a postulate in the theory or electrodynamics and relativity. The law states that any charged particle moving in an EM field is subjected to the force

    F = q(E + vxB)

    This is called the Lorentz Force Law. It seems like I did something more with this in the past year but I don't recall where I put it. I'll get back to you if I think of it.

    Pete
     
  8. Jan 24, 2005 #7

    DB

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    thanks pete
     
  9. Jan 24, 2005 #8

    pervect

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    One can set the direction of the E field at a particular point to be any desired direction with a pair of parallel charged plates. One can indpendently set the direction of the B field with a magnet or electromagnet. Therefore E and B do not have to be perpendicular.
     
  10. Jan 24, 2005 #9
    Are you sure. I don't see how this can be done indepently of each other. Please elaborate because i really would like to know.

    After introdicing the B-field, it WILL have influence on the already present E-field and the other way around. This is basic electrostatics and magnetostatics...

    marlon
     
  11. Jan 24, 2005 #10

    dextercioby

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    Marlon,please "elaborate" on the "magnetostatics,electrostatics" and the "influnce" of B over E...

    Daniel...

    P.S.U got me all confused,man...Are u trying to rewrite electrodynamics...?? :confused:
     
  12. Jan 24, 2005 #11
    What do you mean ???

    Are you saying you don't know what electrostatics and magnetostatics are ???


    marlon :uhh:
     
  13. Jan 24, 2005 #12

    dextercioby

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    :rofl: :rofl: Me????????????Maybe,u...U didn't answer (intentionally avoided) my question...

    What have electrostatics,magnetostatics and "field influence" in common??

    Daniel.
     
  14. Jan 24, 2005 #13
    Well, i am very sorry but if you claim to know these subjects then why are you asking about the connection between the E-field and the B-field???

    Really, what are you trying to prove here ???

    marlon
     
  15. Jan 24, 2005 #14

    dextercioby

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    That u made an erroneous remark... :uhh:

    Daniel.
     
  16. Jan 24, 2005 #15
    Hmmm

    then what, according to you is wrong about my remark ???

    marlon
     
  17. Jan 24, 2005 #16

    dextercioby

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    To me this sounds very conspicuous... :yuck: Electrostatics and magnetostatics have nothing in common with B->E and viceversa...
    Please take another look at the equations of electrostatics & magnetostatics and tell me i'm right... :tongue2:

    Daniel.
     
  18. Jan 24, 2005 #17
    This is not a reason. Again i ask you : what is wrong with my remark???

    marlon

    Are you saying that the E field and the B field have no mutual connection...We are talking about the combination of both these subjects...
     
  19. Jan 24, 2005 #18

    dextercioby

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    Marlon,i ain't gonna quote you on each reply...It's not magntostatics and neither electrostaics involved when discussing the "bond" between the electric field & the magnetic field...
    Your mistake was insterting the 2 long words in the paragraph they should have never been in the first place.Plus the rather dubious:
    What is basic electrstatics and magnetostatics...??

    Daniel.

    P.S.Damn,i quoted u again... :tongue2:
     
  20. Jan 24, 2005 #19
    Sighs,...please, stop starting discussions based upon personal views...

    marlon

    ps : basic means elementary :wink:
     
  21. Jan 24, 2005 #20

    dextercioby

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    Is that a rather elegant way to end discussions in which u're wrong...?? :wink:

    Daniel.

    P.S.Maybe i'll teach QM one day and i'll surely as hell won't use the word "orbital" as a substantive... :tongue2:
     
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