Magnetic Material Mahatma Gandhi Institute Of Technical Education & Research Center Navsari Prepaid by Patel Nirav N Patel Vishal H Ranipa Ashish M

Magnetic Material

 Ferromagnetism  Ferrimagnetism  Diamagnetism  Ant ferromagnetism  Hard magnet Classification of Magnetic Materials

 Ferromagnetism - Alignment of the magnetic moments of atoms in the same direction so that a net magnetization remains after the magnetic field is removed.  Ferrimagnetism - Magnetic behavior obtained when ions in a material have their magnetic moments aligned in an antiparallel arrangement such that the moments do not completely cancel out and a net magnetization remains.  Diamagnetism - The effect caused by the magnetic moment due to the orbiting electrons, which produces a slight opposition to the imposed magnetic field.  Ant ferromagnetism - Arrangement of magnetic moments such that the magnetic moments of atoms or ions cancel out causing zero net magnetization.  Hard magnet - Ferromagnetic or ferromagnetic material that has a coercively > 10 4 A. m -1.

 Soft Magnetic Materials - Ferromagnetic materials are often used to enhance the magnetic flux density (B) produced when an electric current is passed through the material. Applications include cores for electromagnets, electric motors, transformers, generators, and other electrical equipment.  Data Storage Materials - Magnetic materials are used for data storage.  Permanent Magnets - Magnetic materials are used to make strong permanent magnets  Power - The strength of a permanent magnet as expressed by the maximum product of the inductance and magnetic field. Applications of Magnetic Materials

Magnetization

 Magnetization refers to the process of converting a non-magnetic material into a Magnetic material.  The intensity of Magnetization is directly related to the applied field H.

Magnetization

Permeability: ( µ )

The Magnetic induction B is proportional to the applied Magnetic field intensity H. Where µ permeability of a medium

Relative permeability µ r  The ratio of permeability of medium to the permeability of free space is called relative permeability µ r of the solid.

Boundary Conditions

 Within a homogeneous medium, there are no abrupt changes in H or B. However, at the interface between two different media (having two different values of m), it is obvious that one or both of these must change abruptly.

Boundary Conditions (Cont’d)  The normal component of a solenoid vector field is continuous across a material interface:  The tangential component of a conservative vector field is continuous across a material interface:

Boundary Conditions (Cont’d)  The tangential component of H is continuous across a material interface, unless a surface current exists at the interface.  When a surface current exists at the interface, the BC becomes

Boundary Conditions (Cont’d)  In a perfect conductor, both the electric and magnetic fields must vanish in its interior. Thus,  a surface current must exist  the magnetic field just outside the perfect conductor must be tangential to it.

Magnetic Circuits

Magnetic Circuit Definitions  Magneto motive Force  The “driving force” that causes a magnetic field  Symbol, F  Definition, F = NI  Units, Ampere-turns, (A-t)

Magnetic Circuit Definitions  Magnetic Field Intensity  MMF gradient, or MMF per unit length  Symbol, H  Definition, H = F/l = NI/l  Units, (A-t/m)

Magnetic Circuit Definitions  Flux Density  The concentration of the lines of force in a magnetic circuit  Symbol, B  Definition, B = Φ/A  Units, (Wb/m 2 ), or T (Tesla)

Magnetic Circuit Definitions  Reluctance  The measure of “opposition” the magnetic circuit offers to the flux  The analog of Resistance in an electrical circuit  Symbol, R  Definition, R = F/Φ  Units, (A-t/Wb)

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