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A Problem with Two Current-Carrying Wires

  1. May 11, 2013 #1
    We all know that there is a force between them. But I wonder... if electrons in both wires are moving with the same speed the relative velocity between the electrons in wire A and B equals zero - but then there would be no magnetic field and no force. Could you help me with this?
  2. jcsd
  3. May 11, 2013 #2


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    Staff: Mentor

    There is a magnetic field and a force in the lab frame. In the frame of the electrons, there is not - but then you have protons moving in the opposite direction.
  4. May 11, 2013 #3


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    Staff: Mentor

    Also, in the electrons' rest frame, the positive and negative charge densities are different, so there is a net electrostatic force in addition to the magnetic force between the protons.
  5. May 12, 2013 #4
    They also discovered that a pair of wires of thin guage (insulated) will accidentally become an antenna and cause frequency problems in certin applications.
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