Question

At a place of latitude $5{}^\circ$, the angle of dip is nearly
A.$5{}^\circ$
B.$10{}^\circ$
C.$7.5{}^\circ$
D.$2.5{}^\circ$

Answer 1

The angle of dip also known as the magnetic dip is the angle between the magnetic field lines of the Earth and the horizontal axis. The tan angle of dip is twice the tan of angle of declination. Hence by using this concept, we can solve the given problem easily.

Complete answer:
The angle of declination is the angle between the geographical meridian of the Earth and its magnetic meridian. It varies from place to place. In the question, it is given that the angle of declination is:
$\delta =5{}^\circ$
The relation between angle of dip and angle of declination of a particular point is as follows:
$\tan \theta =2\tan \delta$
For small latitudes, as given in the question we can say that,
$\theta \simeq 2\delta$
Now, after making these approximations as stated above we shall put the value of angle of declination that is given in the question to proceed further,
$\begin{aligned} & \theta =2\times 5{}^\circ \\\ & \therefore \theta =10{}^\circ \\\ \end{aligned}$

Therefore, the correct option is $B$.

The angle of dip changes from point to point as the angle of declination changes. If the angle of declination is not small, then we cannot consider the approximation of $\theta \simeq 2\delta$ that we had made earlier to solve this question.

Note:
The angle of dip at the North pole is $+90{}^\circ$ while at the South pole it is $-90{}^\circ$. The angle of dip for any latitude lies between this range. The equator has an angle of dip of $0{}^\circ$. The locus of the line joining all the points at the equator is also known as the aclinic line.