At a temperature of $30\,^oC$,the susceptibility of a ferromagnetic material is found to be $\chi$. Its susceptibility at $333\,^oC$ is....$\chi$.

$A$ magnetizing field of $5000 \ A/m$ produces a magnetic flux of $4 \times 10^{-5} \ Wb$ in an iron rod of cross-sectional area $0.4 \ cm^2$. The permeability of the rod in $Wb/(A \cdot m)$ is:

$A$ Rowland ring of mean radius $15\; cm$ has $3500$ turns of wire wound on a ferromagnetic core of relative permeability $800$. What is the magnetic field $B$ (in $T$) in the core for a magnetizing current of $1.2\; A$?

The relative permeability of iron is $5500$. What will be its magnetic susceptibility?

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 $....\pi \times 10^{-4} \text{ H/m}$.

Which of the following relations is incorrect?
$(a) \ B = \mu_0(H + I)$
$(b) \ B = \mu_0(H + \chi_m)$
$(c) \ \mu_r = 1 + \chi_m$
$(d) \ \chi_m = I / H$
(Here,$I =$ intensity of magnetization and $H =$ magnetising field)