An iron ring of relative permeability ${\mu }_r$ has windings of insulated copper wire of $n$ turns per metre. When the current in the windings is $I$, find the expression for the magnetic field in the ring.

The following figure shows the variation of intensity of magnetisation versus the applied magnetic field intensity, $H$, for two magnetic materials $A$ and $B$.

Identify the materials $A$ and $B$.

The following figure shows the variation of intensity of magnetisation versus the applied magnetic field intensity, $H$, for two magnetic materials $A$ and $B$.

For the material $A$, plot the variation of intensity of magnetisation versus temperature.

The following figure shows the variation of intensity of magnetisation versus the applied magnetic field intensity, $H$, for two magnetic materials $A$ and $B$:

Identify the materials $A$ and $B$

The following figure shows the variation of intensity of magnetisation versus the applied magnetic field intensity, $H$, for two magnetic materials $A$ and $B$:

Draw the variation of susceptibility with temperature for $B$.