Earth’s magnetic field always has a horizontal component except at
A. Magnetic equator
B. Magnetic pole
C. Geographic north pole
D. At the latitude of ${{45}^{0}}$

Hint: The earth’s magnetic field will have a horizontal component when the magnetic field lines are not perpendicular to the surface of the earth. The direction of the magnetic field at a point is given by the tangent to the magnetic field lines at that point. If the tangent to the field lines is perpendicular to the surface, the magnetic field will also be completely perpendicular to the surface and have no horizontal component.

Complete answer:
The direction of the earth’s magnetic field at a point is given by the tangent to the magnetic field lines at that point. If the tangent is not perpendicular to the surface of the earth at that point, the magnetic field will have a component along the surface of the earth. This component is known as the horizontal component of the earth’s magnetic field at that point.




At the magnetic poles, the magnetic field lines are completely perpendicular to the surface of the earth and so is the tangent to the field lines. Therefore, the direction of the magnetic field at the magnetic poles is completely perpendicular to the surface of the earth and hence, has no component that is parallel to the surface of the earth. Therefore, the horizontal component of the earth’s magnetic field is zero at the magnetic poles.
Hence, Earth’s magnetic field always has a horizontal component except at the magnetic poles where it is zero.

So, the correct answer is “Option B”.

Note:
Students often think that the magnetic poles and the geographic poles on the earth are equal. However, there is a difference in their respective positions and hence even at the geographical poles, the magnetic field has some horizontal component. Students should not confuse between the geographical and the magnetic poles and be aware of this concept.