The vertical component of the Earth's magnetic field is zero at:

Give information about the Earth's magnetic field lines and the location of the magnetic poles.

Explain geographic meridian and magnetic meridian.

The relations among the three elements of Earth's magnetic field,namely horizontal component $H$,vertical component $V$,and angle of dip $\delta$ are,($B_{E} =$ total magnetic field):

$A$ magnetic compass needle oscillates $30$ times per minute at a place where the angle of dip is $45^{\circ}$, and $40$ times per minute at a place where the angle of dip is $30^{\circ}$. If $B_1$ and $B_2$ are respectively the total magnetic field due to the earth at the two places, then the ratio $B_1/B_2$ is best given by:

The intensity of the magnetic field due to the Earth at a point inside a hollow steel box is: