Lines which represent places of constant angle of dip are called

At a certain place,the angle of dip is $30^{\circ}$ and the horizontal component of the Earth's magnetic field is $0.5 \ G$. The Earth's total magnetic field (in $G$) at that place is:

The angle of dip is $90^{\circ}$ at:

The angle between the Earth's magnetic axis and the Earth's geographical axis is approximately $... ^\circ$.

The value of the horizontal component of the earth's magnetic field and the angle of dip are $1.8 \times 10^{-5} \, Wb/m^2$ and $30^{\circ}$ respectively at a certain place. The total intensity of the earth's magnetic field at that place will be:

$A$ dip needle lies initially in the magnetic meridian when it shows an angle of dip $\theta$ at a place. The dip circle is rotated through an angle $x$ in the horizontal plane and then it shows an angle of dip $\theta'$. Then $\frac{\tan \theta'}{\tan \theta}$ is