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

$A$ domain in a ferromagnetic substance is in the form of a cube of side $1 \mu m$. If it contains $8 \times 10^{10}$ atoms and each atomic dipole has a dipole moment of $9 \times 10^{-24} \ A \cdot m^{2}$,then the magnetisation of the domain is

$A$ 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 magnetic susceptibility is defined as:

$A$ 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 $9.27 \times 10^{-24}\; A m^2$.

The magnetic moment produced in a substance of mass $5 \ g$ is $6 \times 10^{-7} \ A \cdot m^{2}$. If its density is $5 \ g/cm^{3}$,then the intensity of magnetization in $A/m$ will be: