The Earth's magnetic equator passes through Jos in Nigeria. At Jos, the

Analysis of the Question

This question tests your understanding of Terrestrial Magnetism, specifically the concept of the Angle of Dip (or Inclination). You are asked to identify the physical characteristic of the Earth's magnetic field at the magnetic equator.

Concept Explanation

The Angle of Dip is the angle that the Earth's magnetic field makes with the horizontal at any point on the Earth's surface.

1. At the Magnetic Poles: The magnetic field lines are perpendicular to the Earth's surface. Therefore, the angle of dip is 90°.
2. At the Magnetic Equator: The magnetic field lines are parallel to the Earth's surface. Because the field is perfectly horizontal, it makes an angle of 0° with the horizontal.

In Nigeria, Jos is geographically significant in physics because it is located very close to the magnetic equator. Consequently, a magnetic needle suspended freely at Jos will remain perfectly horizontal.

Step-by-Step Solution

• Step 1: Recall the definition of the magnetic equator. It is the line where the Earth's magnetic field is horizontal.
• Step 2: Relate this to the angle of dip. Since the field is horizontal, the angle between the field and the horizontal plane is 0°.
• Step 3: Evaluate the options: • A: Angle of variation (declination) is not necessarily zero at the equator; it depends on the specific location. • B: Magnetic declination is the angle between true north and magnetic north; it is not 90° at the equator. • C: The angle of dip is the angle of inclination. At the magnetic equator, this is 0°. This matches our definition. • D: The horizontal component of the Earth's field is at its maximum at the equator, not zero. (The vertical component is zero at the equator).

Conclusion

Since the magnetic field is horizontal at the magnetic equator, the angle of dip is 0°. This confirms that option C is the correct statement.

Exam Tip

Remember the "90-0-90" rule for the Earth's magnetic field:

• At the Poles, the angle of dip is 90°.
• At the Equator, the angle of dip is 0°.
• If you ever forget, visualize a compass needle: at the equator, it stays flat (0°), but if you were at the North Pole, it would try to point straight down into the ground (90°).