Question

At certain place, the horizontal component of earth’s magnetic field is $3.0G$ and the angle dip at that place is $30^{\circ }$. The magnetic field of earth at that location

• A. 4.5 G
• B. 5.1 G
• C. 3.5 G
• D. 6.0 G

Answer 1

Answer: (C)

Given, $H=3.0$ gauss
Angle of dip, $\delta =30^{\circ }$
$\frac{H}{B}=\cos \delta$
$H=B\cos \delta$
$3.0=B\times \cos 30^{\circ }$
$B=\frac{3.0}{\cos 30^{\circ }}=\frac{3}{\sqrt{3}/2}=\frac{2\times 3}{\sqrt{3}}$
$=\frac{6}{1.73}=3.5G$