$A$ dip circle lies initially in the magnetic meridian,it shows an angle of dip $\delta$ at a place. The dip circle is rotated through an angle $\alpha$ in the horizontal plane and then it shows an angle of dip $\delta^{\prime}$. Hence $\frac{\tan \delta^{\prime}}{\tan \delta}$ is

$A$ bar magnet $A$ of magnetic moment $M_A$ is found to oscillate at a frequency twice that of magnet $B$ of magnetic moment $M_B$ when placed in a vibrating magnetometer. We may say that

The frequency of vibration in a vibration magnetometer of the combination of two bar magnets of magnetic moments $M_1$ and $M_2$ is $6 \ Hz$ when like poles are tied together and it is $2 \ Hz$ when the unlike poles are tied together, then the ratio $M_1: M_2$ is

$A$ magnet is suspended in the magnetic meridian with an untwisted wire. The upper end of the wire is rotated through $180^o$ to deflect the magnet by $30^o$ from the magnetic meridian. When this magnet is replaced by another magnet,the upper end of the wire is rotated through $270^o$ to deflect the magnet $30^o$ from the magnetic meridian. The ratio of the magnetic moments of the magnets is

$A$ neutral point is obtained at the centre of a vertical circular coil carrying current. The angle between the plane of the coil and the magnetic meridian is.......$^o$

At a certain place, a magnet makes $30$ oscillations per minute. At another place where the magnetic field is double, its time period will be: