If the relative permeability of iron is $5500$, then its magnetic susceptibility is:

$A$ rod of ferromagnetic material with dimensions $10 \, cm \times 0.5 \, cm \times 0.2 \, cm$ is placed in a magnetic field of strength $0.5 \times 10^4 \, Am^{-1}$. As a result,a magnetic moment of $5 \, Am^2$ is produced in the rod. The value of magnetic induction will be.... $T$

The magnetic susceptibility of a material of a rod is $499$. Permeability in vacuum is $4\pi \times 10^{-7} \text{ H/m}$. Absolute permeability of the material of the rod is $....\pi \times 10^{-4} \text{ H/m}$.

$A$ material of $0.25 \ cm^2$ cross-sectional area is placed in a magnetic field of strength $(H) 1000 \ Am^{-1}$. Then,the magnetic flux produced is (Susceptibility of material is $313$) (Permeability of free space,$\mu_0 = 4 \pi \times 10^{-7} \ Hm^{-1}$)

$A$ 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 $S.I.$ unit of magnetic permeability is