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

When a piece of a ferromagnetic substance is placed in a uniform magnetic field,the flux density inside it is four times the flux density away from the piece. The magnetic permeability of the material is

Obtain the relation between magnetisation $\vec{M}$ and magnetic intensity $\vec{H}$ for a solenoid.

$A$ domain in a ferromagnetic substance is in the form of a cube of side length $2 \mu m$. It contains $4 \times 10^{14}$ atoms and each atomic dipole has a moment of $16 \times 10^{-24} \text{ A m}^2$. The magnetization of the domain is . . . . . . .

The magnetic susceptibility of iron is $5499$. The relative permeability of iron will be

An iron rod of volume $10^{-3} \ m^3$ and relative permeability $1000$ is placed as a core in a solenoid with $10 \ turns/cm$. If a current of $0.5 \ A$ is passed through the solenoid,then the magnetic moment of the rod will be $........... \ Am^2$.