If the dip circle is set at $45^{\circ}$ to the magnetic meridian,then the apparent dip is $30^{\circ}$. The true dip of the place is:

$A$ compass needle will show which one of the following directions at the Earth's magnetic pole?

The Earth's magnetic field at a certain place has a horizontal component of $0.3 \ G$ and the total strength of $0.5 \ G$. The angle of dip is:

Consider the plane $S$ formed by the dipole axis and the axis of the Earth. Let $P$ be a point on the magnetic equator and in plane $S$. Let $Q$ be a point of intersection of the geographical and magnetic equators. Obtain the declination and dip angles at $P$ and $Q$.

At some location on Earth,the horizontal component of Earth's magnetic field is $18 \times 10^{-6} \ T$. At this location,a magnetic needle of length $0.12 \ m$ and pole strength $1.8 \ A \ m$ is suspended from its mid-point using a thread. It makes a $45^{\circ}$ angle with the horizontal in equilibrium. To keep this needle horizontal,the vertical force that should be applied at one of its ends is:

The magnetic compass is not useful for navigation near the magnetic poles because