Magnetic Permeability and Classification of Materials on its Basis
Magnetic permeability is defined as a relative rise or fall in the resultant magnetic field inside the materials compared to the magnetizing field, in which material is placed. It is also defined as the ability of material to support the development of magnetic field i.e. the ease of external applied field with which it can magnetize the material placed in it. It is the degree of magnetization in response to the applied field. In mathematical terms, it can be defined as μ = B/H here, “B” is the magnetic flux density that is built inside material and “H” is the the strength of magnetizing field. “μ” is a greek letter, called mu. “H” is the measure of that magnetizing field which is produced due to the electric current flow. “B” is the measure of that magnetic field which is taken as concentration of magnetic field lines per unit cross sectional area. Φ = B.A B = Φ/A In free space, both magnetizing field and magnetic flux density i.e. B and H are same because there is no matter to modify the field. Units In CGS unit system, permeability is a dimensionless quantity. However in MKS system, B and H have different units so permeability was defined as 4 π ×10-7 weber per ampere meter. The permeability is also measured in terms of Henries/meter , which has dimensions of inductance per unit length. Absolute and relative permeability Here permeability is called absolute permeability i.e. ratio of magnetic flux density to magnetic field strength (B/H). Relative permeability “μr” is a ratio given as μ/ μo , so it is dimensionless quantity whose value is 1 for space. Magnetic susceptibility Magnetic susceptibility specifies whether a material will be attracted into or repelled out of a magnetic field. It is the measure of how much a material will become magnetized by the application of applied magnetic field. Mathematically, it is the ratio of M to H. “M” is magnetic moment per unit volume. “H” is intensity of magnetizing field.
Classification of materials On the basis of permeability and magnetic behaviors, materials can be classified into categories. Diamagnetic material has relative permeability which is less than 1. When such materials are placed in external magnetic field, external field is partly expelled due to which flux density is slightly reduced in material. Material creates a magnetic field in opposite direction t applied field. E.g. bismuth. Paramagnetic material has relative permeability more than one. Such material becomes slightly magnetized in direction of applied field, when it is placed in external magnetic field. E.g. platinum. Ferromagnetic material doesn’t have constant permeability. Relative permeability increases as external magnetizing field increases, then decreases after reaching a maximum value. E.g. iron. Do not forget leaving your valuable comment on this piece of writing and sharing with your near and dear ones. To keep yourself up-to-date with Information Palace, put your email in the space given below and Subscribe. Furthermore, if you yearn to know about Ductile and Brittle Materials, view our construct, ‘Difference between Ductile and Brittle Materials with Stress Strain Curve.’ Read the full article
