A magnetic needle has a magnetic moment of $$5 \times 10^{-2} \mathrm{~Am}^2$$ and moment of inertia $$8 \times 10^{-6} \mathrm{~kgm}^2$$. It has a period of oscillation of $$2 \mathrm{~s}$$ in a magnetic field $$\mathbf{B}$$. The magnitude of magnetic field is approximately?

A circular current loop of magnetic moment $$M$$ is in a arbitrary orientation in an external uniform magnetic field $$\mathbf{B}$$. The work done to rotate the loop by $$30^{\circ}$$ about an axis perpendicular to its plane is

In a permanent magnet at room temperature