A bar magnet is oscillating in Earth's magnetic field with the time period $\mathrm{T}$. If a similar magnet with the same mass and dimensions has magnetic dipole moment $4$ times that of this magnet, then the periodic time will be______.

 

 

An electric dipole of moment $\overrightarrow{\mathrm{P}}$ is placed in a uniformed magnetic field $\overrightarrow{\mathrm{E}}$. The dipole is rotated through a very small angle $\theta$ from equilibrium and is released. Prove that it executes simple harmonic motion with periodic time 

$\mathrm{T}=2\mathrm{\pi }\sqrt{\frac{\mathrm{I}}{\mathrm{PE}}}$ where $\mathrm{I}$= moment of inertia of the dipole.

Which one of the following represents Curie's law?