Magnetic meridian is an imaginary:

Options

A. a point
B. a line along north-south
C. a horizontal plane
D. a vertical plane

Answer

To solve the question regarding the definition of a magnetic meridian, we will break down the explanation into clear steps.

### Step-by-Step Solution:

1. **Understanding the Concept of Magnetic Meridian**:
- The magnetic meridian is defined as a vertical plane that passes through the magnetic axis of a freely suspended magnet.

2. **Visualizing the Magnet**:
- Imagine a bar magnet with a north pole and a south pole. When this magnet is freely suspended, it aligns itself along the magnetic meridian.

3. **Defining the Magnetic Axis**:
- The magnetic axis is an imaginary line that runs from the north pole to the south pole of the magnet. The magnetic meridian, therefore, is the vertical plane that includes this magnetic axis.

4. **Magnetic Meridian in the Context of Earth**:
- When we refer to the magnetic meridian in relation to Earth, it is a vertical plane that connects the Earth's magnetic north and south poles.

5. **Relation to Geographical Meridian**:
- The geographical meridian is a similar concept but refers to the geographical north and south poles. Both meridians are vertical planes, but they differ based on the poles they connect.

6. **Characteristics of Magnetic Meridian**:
- The magnetic meridian is always parallel to the magnetic lines of force. It can also be described as the horizontal component of the magnetic force lines on the surface of the Earth.

7. **Evaluating the Options**:
- Given the options in the question:
- A magnetic meridian is not an imaginary point.
- It is not merely a line along north to south.
- It is not a horizontal plane.
- The correct definition is that it is a vertical plane.

8. **Conclusion**:
- Therefore, the correct answer is that the magnetic meridian is an imaginary vertical plane that passes through the magnetic axis of a freely suspended magnet or connects the north and south poles.

### Final Answer:
Magnetic meridian is an imaginary vertical plane that passes through the magnetic axis of a freely suspended magnet.