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

For a paramagnetic substance, the magnetic susceptibility is

The magnetic susceptibility of a paramagnetic material at $$-73^{\circ} \mathrm{C}$$ is 0.0075. Its value at $$-173^{\circ} \mathrm{C}$$ will be

If the angle of dip at places $$A$$ and $$B$$ are $$30^{\circ}$$ and $$45^{\circ}$$ respectively, then the ratio of horizontal component of earth's magnetic field at $$A$$ to that at $$B$$ will be $$\left[\sin 45^{\circ}=\cos 45^{\circ}=\frac{1}{\sqrt{2}}, \sin \frac{\pi}{6}=\frac{1}{2}, \cos \frac{\pi}{6}=\frac{\sqrt{3}}{2}\right]$$