AIIMS 2015 Physics World Records MCQ Question

The magnetic permeability ($\mu$) of a material measures how easily it can be magnetized when placed in an external magnetizing field ($H$). It is defined by the ratio of magnetic flux density ($B$) to the magnetizing field intensity ($H$):$\mu = \frac{B}{H}$For ferromagnetic materials, the relationship between $B$ and $H$ is highly non-linear and depends on the alignment of magnetic domains. This behavior can be understood by looking at the magnetization curve:Initial Stage (Below Saturation): When the magnetizing field ($H$) is initially increased from zero, the magnetic domains inside the ferromagnetic material align rapidly. This causes the internal magnetic flux density ($B$) to grow at a much faster rate than $H$. Because $B$ increases faster than $H$, the permeability ($\mu = \frac{B}{H}$) increases to a peak value.Saturation Stage: As $H$ is increased further, almost all the magnetic domains become fully aligned with the external field. The material reaches magnetic saturation. Beyond this point, any further increase in $H$ results in very little additional increase in $B$. Since $H$ keeps growing while $B$ stays nearly constant, the ratio $\mu = \frac{B}{H}$ begins to decrease.Because the permeability first increases to a maximum and then decreases as it approaches saturation, increasing the magnetizing field may increase or decrease the permeability depending on the current state of magnetization.