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Understanding Magnetic Permeability

  1. Aug 23, 2015 #1
    As per some websites that I visited,
    "Magnetic Permeability is the ability of a material to support the formation of a magnetic field"
    so in materials with higher permeability the magnetic fields should be denser that materials with lower permeability.

    Lets say we have a magnetic circuit with a magnetic material of permeability 1000 and there are 500 flux lines passing through it now if I introduce another material into this circuit with permeability 100 so that both magnetic materials are in series circuit.

    Would the 500 flux lines still force themselves through this material or would there be a drop in flux lines?
  2. jcsd
  3. Aug 23, 2015 #2
    According to your question i think that if you form series magnetic circuits with the help of the permanent magnet,the magnetic lines of force will be from north pole to south pole.
    Thus two magnets which can attract will form the magnetic circuit.So both the magnets will have magnetic lines of force from north pole to south pole,and thus these lines of force assist each other.So there won't be any drop.
  4. Aug 23, 2015 #3
    Actually there are 2 circuits to be compared for flux
    1. Magnet + Core (Perm = 1000)
    2. Magnet + Core (Perm = 1000) + Core (Perm = 100)
  5. Aug 24, 2015 #4


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    There are two measures of magnetic field. One is magnetic field strength, commonly denoted by H and measured in A/m. The other is magnetic flux density, denoted by B and measured in Tesla. The relationship between them is
    B = u uo H
    u is the magnetic permeability and u0 is magnetic 'constant'
    Magnetic field strength H, is related to the source. In fact, if you integrate H over a closed loop, it equals to the current enclosed by the loop.
    Flux density is the quantity that describes things like forces on moving charges, induced voltage when magnetic field changes with time.
    Therefore, if you had two cores same dimensions but different permeability, the magnetic field strength would be the same for both of them, but the flux density would be higher for the higher permeability core.
    If you have materials with different permeability connected in series, it is the magnetic flux density that is constant across the boundary.
    However, the actual field also depends on the length of the magnetic loop and also changes in cross-sectional area of the magnetic circuit. You can search for Kirchoff's law for magnetic circuits for details.

    But coming to your question. I presume that the second circuit will have an extra piece of lower permeability inserted into the first one. In that case, the magnetic flux density for the second circuit would be lower. Actually, just making the magnetic circuit longer will decrease the flux density.
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