Let the magnetic field on earth be modeled by that of a point magnetic dipole at the centre of earth. The angle of dip at a point on the geographical equator is

Options

A. always zero
B. positive, negative or zero
C. unbounded
D. always negative

Explanation

To solve the problem regarding the angle of dip at a point on the geographical equator, we will follow these steps:

### Step 1: Understand the Concept of Angle of Dip
The angle of dip (or magnetic inclination) is the angle that the Earth's magnetic field makes with the horizontal plane. At the geographical equator, we need to analyze how the magnetic field behaves.

**Hint:** Recall that the angle of dip is influenced by the orientation of the magnetic field lines relative to the Earth's surface.

### Step 2: Analyze the Position of the Geographical Equator
The geographical equator is an imaginary line that divides the Earth into the Northern and Southern Hemispheres. At this location, we need to consider the behavior of the Earth's magnetic field.

**Hint:** Consider how the magnetic field lines are oriented at the equator compared to the magnetic poles.

### Step 3: Magnetic Field Behavior at the Equator
At the geographical equator, the magnetic field lines are horizontal. This means that the angle of dip at this point should theoretically be zero since there is no vertical component to the magnetic field.

**Hint:** Visualize the magnetic field lines; they run parallel to the surface at the equator.

### Step 4: Conclusion on the Angle of Dip
Since the magnetic field lines are horizontal at the geographical equator, the angle of dip is indeed zero. Therefore, we can conclude that the angle of dip at a point on the geographical equator is zero degrees.

**Hint:** Remember that the angle of dip can change as you move away from the equator towards the poles.

### Final Answer
The angle of dip at a point on the geographical equator is **0 degrees**.