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Static Magnetic Fields and Effect on ESR

Discussion in 'Electronic Design' started by D from BC, May 5, 2007.

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  1. D from BC

    D from BC Guest

    I have a goofy question and I can't find my old college physics
    books.. :(

    When two identical repelling electromagnets are brought close
    together, does the DC current change?

    Details
    * Constant V across e-magnets
    * Assume no wire heating effects
    * The DC current is measured when the electromagnets are motionless.

    Q2:
    Do different levels of DC across a toroid inductor affect the ESR?
    (Assume no wire heating effects..)
    D from BC
     
  2. John Larkin

    John Larkin Guest

    The current changes transiently as they are brought together...
    increases I think. Then it decays exponentially back to the original
    steady-state value, E/R. So it depends on your definition of "DC."
    Depends on your definition of ESR, but if you mean AC impedance, for a
    ferrous core, yes. For an air core, no.

    John
     
  3. MooseFET

    MooseFET Guest


    Lense's law implies an increase.



    I think there is a small increse in the DC resistance too. It is
    unlikely that you will ever see it in a real situation but perhaps at
    some extreme it will show up. The electrons flowing in the copper
    will have their paths deflected slightly by the field.
     
  4. jasen

    jasen Guest

    Seeing as it's you, (and not another homework question) I won't take it
    literally.

    If I can also ignore any magnetostrictive effects and only measure the
    steady state (and not what happens immediately after the magnets stop moving)
    the answer is no.
    no, but it can effect inductance if it's saturable.

    Bye.
    Jasen
     
  5. D from BC

    D from BC Guest

    Yeah...I know its a homeworky type question... :)

    I didn't think static magnetic fields significantly affect wire
    current density but wasn't sure...
    (Ex..permanent magnet resting on a wire. )

    For example...
    I"ve never heard if wire conducts more (or less) at the north pole.
    (neglecting temperature effects )
    Could be the start of another speaker wire myth...
    Better sound at the North pole... :)

    D from BC
     
  6. John Larkin

    John Larkin Guest

    I suppose that happens in a straight conductor in free space too, a
    sort of spiral electron path due to Hall effect. So Mr Ohm was wrong
    after all!

    Gosh.

    John
     
  7. John Larkin

    John Larkin Guest

    There would be a Hall potential developed in the wire at certain
    magnetic field orientations, and that could increase resistance
    slightly. I don't know if it's enough to measure, probably not.

    Yup, Hall Effect Harmonic Distortion. You heard it here first.

    John
     
  8. D from BC

    D from BC Guest

    lol :)
    D from BC
     
  9. What you mean is the Lorentz force which in turn causes the Hall effect.

    robert
     
  10. Great. Another market for my cow magnet business. The gas mileage boost
    scam was getting a bit old.
     
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