Question

Name three elements of the Earth’s magnetic field which help in defining the Earth’s magnetic field completely.

Answer 1

Hint: The earth rotates along its orbit. Hence due to the presence of ferromagnetic substances in the Earth’s core a net magnetic field is generated. The three elements of the Earth’s magnetic field are used to describe the field at different positions. The first is the angle between the geographic plane of the Earth and the Magnetic meridian plane of the Earth. The second element is the angle between the total magnetic field of the earth and the horizontal line in the magnetic meridian. The third element is the horizontal component of the magnetic field itself at any point.

Complete answer:
Now let us visualize each element and describe them.

The angle between the plane passing through the geographic axis and the plane passing through the Magnetic meridian of the Earth is called angle of magnetic declination. In the above figure it is denoted by $\text{ }\!\!\delta\!\!\text{ }$. This is the first element of the magnetic field of the Earth that we defined.

Now let us define the next element.

The angle between the direction of the intensity of total Earth’s magnetic field and the horizontal line which is perpendicular to the line drawn from the centre of the Earth is called the angle of inclination or angle of dip. In the above figure it is denoted by $\phi $. This is the second magnetic element of the Earth.
If we consider the above diagram the Earth's total magnetic field at point P can be broken into two components The horizontal component is the third and the final element of the Earth’s magnetic field

Note:
It is to be noted that the angle of dip at the equator is zero because the vertical component of the total Earth’s magnetic field is zero. While at the two poles the angle of dip is maximum as the horizontal component of the total Earth’s magnetic field is zero. One more important point to be kept in mind is that the magnetic poles of the earth are different from the geographical poles of the Earth.