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Why magnetic field from a current carrying conductor obey inverse-square law?

  1. Nov 14, 2012 #1
    I have read that the electric field from a point charge fall off as 1/(r*r) since it is analogous to
    variation of intensity of radation from source (whose geometric proof depends on solid-angle), similarily is there any geometric explanation why magnetic field in the stated case fall off as 1/(r*r).
  2. jcsd
  3. Nov 14, 2012 #2
    Bizarre "proof" that the static electric field is analoguous to a radiation... What about the gluon force? It increases over distance. What tells the previous reason in this case?

    As for the static magnetic field... It cannot decrease as 1/R^2 because this would need a permanent current in an open wire. Either it's static, and then you need to close the circuit, and this loop creates a field as 1/R^3, or you have an antenna which accepts only AC current, and radiates an electromagnetic field, not a static magnetic one.

    So 1/R^2 exists only as a computation intermediate of static magnetic fields.
  4. Nov 14, 2012 #3
    It doesn't, does it?
    The magnetic field of an infinite, linear conductor goes like 1/r where r is the distance from the wire (along the radius of a cylinder coaxial with the wire).
    Maybe you mean a different geometry of the current carrying conductor?
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