The period of oscillation of a vibration magnetometer depends on which of the following factors? (where $I$ is the moment of inertia of the magnet about the axis of suspension,$M$ is the magnetic moment of the magnet,and $H$ is the external magnetic field.)

The strength of the magnetic field in which the magnet of a vibration magnetometer is oscillating is increased $4$ times its original value. The frequency of oscillation would then become

When two magnets of equal pole strength and length are placed with their dissimilar poles on the same side,what will be their time period?

In a tangent galvanometer,a current of $0.1 \, A$ produces a deflection of $30^\circ$. The current required to produce a deflection of $60^\circ$ is ...... $A$.

Two bar magnets $A$ and $B$ are placed one over the other and are allowed to vibrate in a vibration magnetometer. They make $20$ oscillations per minute when the similar poles of $A$ and $B$ are on the same side, while they make $15$ oscillations per minute when their opposite poles lie on the same side. If $M_A$ and $M_B$ are the magnetic moments of $A$ and $B$ and if $M_A > M_B$, the ratio of $M_A$ and $M_B$ is

$A$ magnetic needle suspended horizontally by an unspun silk fibre,oscillates in the horizontal plane because of the restoring force originating mainly from