Lines which represent places of constant angle of dip are called

Assertion : In high latitudes,one sees colourful curtains of light hanging down from high altitudes.
Reason : The high-energy charged particles from the sun are deflected to polar regions by the magnetic field of the earth.

The angle of dip at a place is $30^{\circ}$,and the horizontal component of the Earth's magnetic field is $5 \times 10^{-5} \, T$. Calculate the vertical component and the total magnetic field at that place.

If a magnet is suspended freely such that it can rotate about its magnetic axis,in which plane does it come to rest?

The correct relation is:
$B_H$ = Horizontal component of earth's magnetic field; $B_V$ = Vertical component of earth's magnetic field and $B$ = Total intensity of earth's magnetic field.

Explain the magnetic field of the Earth and give the order of magnitude of the Earth's magnetic field.