A dip needle free to move in a vertical plane perpendiculr to the magneetic meridian will remain

Options

A. Horizontal
B. Vertical
C. At an angle of `60^(@)` to the vertical
D. At an angle of `45^(@)` to the horizontal

Answer

To solve the problem regarding the behavior of a dip needle free to move in a vertical plane perpendicular to the magnetic meridian, we can break down the explanation into clear steps:

### Step-by-Step Solution:

1. **Understand the Dip Needle**: A dip needle is a magnetized needle that can pivot freely. It aligns itself with the Earth's magnetic field. The needle has two components of the magnetic field acting on it: the horizontal component (Bh) and the vertical component (Bv).

2. **Identify the Magnetic Meridian**: The magnetic meridian is the vertical plane that contains the direction of the magnetic field lines. When we say the dip needle is in a vertical plane perpendicular to the magnetic meridian, it means that the plane of movement does not align with the magnetic field direction.

3. **Components of the Earth's Magnetic Field**: The Earth's magnetic field can be resolved into two components:
- **Horizontal Component (Bh)**: This component acts parallel to the Earth's surface.
- **Vertical Component (Bv)**: This component acts perpendicular to the Earth's surface.

4. **Effect of the Vertical Plane**: When the dip needle is free to move in a vertical plane that is perpendicular to the magnetic meridian, the horizontal component of the Earth's magnetic field (Bh) remains unchanged because the needle's axis of rotation lies in the direction of this horizontal component.

5. **Behavior of the Dip Needle**: Since the dip needle is influenced by the vertical component of the magnetic field (Bv) and the horizontal component (Bh), and given that it is in a vertical plane perpendicular to the magnetic meridian:
- The needle will align itself vertically because the horizontal component does not exert a torque that would cause it to tilt away from the vertical position.

6. **Conclusion**: Therefore, the dip needle will remain in a vertical position.

### Final Answer:
The dip needle will remain **vertical**.