According to Curie's law,the magnetic susceptibility of a substance at an absolute temperature $T$ is proportional to

$A$ solenoid having $400$ turns per metre has a core of a material with relative permeability $400$. When a current of $0.5 \ A$ is passed through it,the magnetization of the core material in $Am^{-1}$ is nearly

$A$ 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,$\mu_0 = 4 \pi \times 10^{-7} \ Hm^{-1}$)

An iron rod of susceptibility $599$ is subjected to a magnetising field of $1200 \, A m^{-1}$. The permeability of the material of the rod is $(\mu_{0} = 4 \pi \times 10^{-7} \, T m A^{-1})$.

$A$ 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 $I_m$.

What is the magnetic susceptibility of a medium if its relative permeability is $0.85$?