The frequency of oscillation of a small magnet in a magnetic field of induction 'B' is '$n$'. If the frequency of oscillations of the same magnet in a field of induction 'X' falls to $\left(\dfrac{n}{3}\right)$, the value of 'X' is

The region inside a current carrying toroid is filled with a material (Niobium) having susceptibility $\chi = 2.6 \times 10^{-5}$. The percentage increase in the magnetic field in the presence of Niobium over that without it, is

The magnetic moment produced in a sample of 2 gram is $8 \times 10^{-7}\,\text{A/m}^2$. If its density is $4\ \text{g/cm}^3$ then the magnetization of the sample is

An iron rod is placed parallel to magnetic field intensity 1000 A/m. The magnetic flux through the rod is $3 \times 10^{-4}$ Wb and its cross-sectional area is $1.5\ \text{cm}^2$. The magnetic permeability of rod in $\text{Wb/}_{\text{A-m}}$ is