Question

The vertical component of Earth's magnetic field is zero at, or the Earth's magnetic field always has a vertical component except at the

• A. magnetic poles
• B. geographic poles
• C. every place
• D. magnetic equator

Answer 1

Answer: (D)

magnetic equator

The magnetic equator is the line where the inclination is zero i.e. vertical component of magnetic field is zero. The vertical component of Earth's magnetic field is,
$B_v=B\sin \theta$
$B_v=B\sin 0^{\circ }$
$B_v=0$
Also, at equator only horizontal component of Earth's magnetic field is there i.e. the magnetic field is horizontal.
Hence,
$B_H=B$
We know
$B_H=B\cos \theta$
$B=B\cos \theta$
$\cos \theta =1$
$\Rightarrow \theta =0^{\circ }$