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B field ?

  1. Jul 6, 2011 #1
    Lets say I have a negative line charge on a long thin rod, if I am at rest with respect to that rod I will see an E field. But If I am moving with respect to that rod I will see a B field. So why are people looking for magnetic monopoles, If B fields are E fields in disguise, wouldn't the electrons need to show magnetic monopoles if they existed?
     
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  3. Jul 6, 2011 #2

    tiny-tim

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    hi cragar! :smile:
    yes, but it's only a tiny-weeny B field …

    it's still mostly an E field :wink:

    E2/c2 - B2 is invariant (the same in all frames), so since it's positive for the stationary rod, it's always positive

    (if the speed is tanhu, then |E| = cE0coshu and |B| = E0sinhu)

    similary, a stationary magnetic monople (if it exists) will have E = 0, and so E2/c2 - B2 will be negative, in that and any other frame …

    there's no frame transformation that will turn pure E into pure B :smile:
     
    Last edited: Jul 6, 2011
  4. Jul 6, 2011 #3
    I though it was E(dot)B that was invariant . Or is your way also equivalent. We can have frames where there is pure B then some E and B, but that probably doesn't help my case.
     
  5. Jul 6, 2011 #4

    tiny-tim

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    Last edited by a moderator: Apr 26, 2017
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