Question

If the horizontal component of the earth's magnetic field is $0.30\,G,$ and the dip angle is $60^{\circ}$ at a given place, then the value of earth's total magnetic field is

• A. $ 0.15\,G $
• B. $ 0.15\,\sqrt{3}G $
• C. $ 0.15\,\sqrt{2}G $
• D. $0.60\,G $

Answer 1

Answer: (D)

$B_{H}=0.30\, G$ Angle of dip $=60^{\circ} B=?$
Earths magnetic field is horizontal only at the magnetic equator.
At any other place, the total intensity can be resolved into horizontal component
$\left(B_{H}\right)$ and vertical component $\left(B_{V}\right)$
Also, $B_{H}=B \cos \phi$ and $B_{V}=B \sin \phi$
where, $\phi$ is angle of inclination or dip
$\therefore 0.30=B \cos 60^{\circ}$
$0.30=\frac{B}{2}$
$\Rightarrow B =0.60\, G$