Physics - Magnetic Materials

Magnetisation vector expression

\overrightarrow{I}=\overrightarrow{\frac{M}{V}}

where,

M = magnetic dipole moment

V = volume

Dipole moment

\overrightarrow{\mu}=i\overrightarrow{A}

Paramagnetic materials

The materials whose atomic dipoles have the tendency to align in the direction of the applied magnetic field thus increasing the MF due to magnetisation.

Ferromagnetic materials

The materials whose atomic dipoles have a strong tendency to align themselves without having to apply any external field.

Diamagnetic materials

They have no net magnetic moment and have the tendency to oppose the applied field by lenz’s law \implies Resultant MF is smaller

Magnetic susceptibility

\chi=\frac{\overrightarrow{I}}{\overrightarrow{H}}

where,

I = magnetisation vector

H = magnetic intensity

Magnetic intensity expression

\overrightarrow{H}=\frac{\overrightarrow{B}}{\mu_{o}}-\overrightarrow{I}

in vacuum,

\overrightarrow{H}=\frac{\overrightarrow{B}}{\mu_{o}}

or

H=\frac{m}{4\pi r^2}

m = pole strength

relative permeability

\mu_{r}=\frac{\mu_{m}}{\mu_{o}}=\frac{B}{B_{o}}

\mu_{r}=1+\chi

where,

\chi=susceptibility

Material used in transformers and moving coil galvanometers

Soft iron as it gets demagnetised after the supply of MF stops