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Magnetic field around a wire near ferrous materials

  1. Jul 11, 2015 #1
    I was wondering if I could ask a question on the magnetic field surrounding a current-carrying wire, and how this field might change with the presence of other, ferrous materials nearby.

    I have been using this web page
    http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/magcur.html#c3
    to calculate the magnetic field around the wire, which the page shows moving in concentric circles.
    The site gives the formula B = (μ0*I)/(2*pi*r) Where I is the current in Amperes, and r is the distance from the wire in meters.
    This formula is for a wire surrounded by air, but I am wondering what might happen if some other objects were close to the wire (as close as r in the formula)

    I am interested in a situation where a high permeability object and a low permeability object are positioned equal distance from the wire.
    I am assuming the presence of the high permeability material would make the magnetic field around the wire stronger.
    Would the field would still flow in a concentric circle, or would the field be diverted in the direction of the high permeability material?
    If the goal was to exert a stronger force on the low permeability object, would the resulting magnetic field have a stronger effect on the low permeability object?
     
  2. jcsd
  3. Jul 11, 2015 #2

    Hesch

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    The magnetic field will be distorted. Think of if you have to travel some ( long ) distance by car, you will prefer to use the highway for a long distance, though the total distance ( distance on highway + distance on smaller roads ) may become some longer. You are choosing the fastest way, not the shortest.

    The material with the high permeability is the highway, air is the smaller road.

    upload_2015-7-11_21-17-45.png
     
  4. Jul 11, 2015 #3

    Hesch

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    Yes, because the path through the air has been shortened a bit, thus the field strength of the magnetic field, measured in the unit [ A/m ], has increased outside the object with high permeability, and thus at the location of the low permeability object. ( I don't know if that is understandable? ).
     
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