The relative permeability of iron is $2000$. Its absolute permeability in $SI$ units will be (given $\frac{\mu_0}{4 \pi} = 10^{-7} \text{ SI units}$):

$A$ solenoid has a core of a material with relative permeability $400$. The windings of the solenoid are insulated from the core and carry a current of $2 \; A$. If the number of turns is $1000$ per metre,calculate $(a) \; H$,$(b) \; M$,$(c) \; B$ and $(d)$ the magnetising current $I_m$.

The basic magnetization curve for a ferromagnetic material is shown in the figure. Then,the value of relative permeability is highest for the point

Give the unit and dimensional formula of magnetisation.

The relationship between the magnetic susceptibility $(\chi)$ and the magnetic permeability $(\mu)$ is given by (where $\mu_0$ is the permeability of free space and $\mu_{r}$ is relative permeability).

$A$ domain in ferromagnetic iron is in the form of a cube of side length $1\; \mu m$. Estimate the number of iron atoms in the domain and the maximum possible dipole moment and magnetisation of the domain. The molecular mass of iron is $55\; g/mol$ and its density is $7.9\; g/cm^3$. Assume that each iron atom has a dipole moment of $9.27 \times 10^{-24}\; A m^2$.