Question

A magnet is place on a paper in a horizontal plane for locating neutral points. A dip needle placed at the neutral point will be horizontal at the

• A. magnetic poles
• B. magnetic equator
• C. latitude angle ${45}^o$
• D. latitude angle of ${60}^o$

Answer 1

The correct option is B magnetic equator

The magnetic equator is the line where the inclination is zero i.e. vertical component of magnetic field is zero, only horizontal magnetic field is present.
Hence,
$B_v=B\sin \theta$
$B_v=B\sin 0^{\circ }$
$B_v=0$
Also,
$B_H=B$
We know
$B_H=B\cos \theta$
$B=B\cos \theta$
$\cos \theta =1$
$\Rightarrow \theta =0^{\circ }$
Since, a dip needle indicate the direction of magnetic field, thus a dip needle placed at the neutral point will be horizontal at the magnetic equator.