The pole pieces of the magnet used in a pivoted coil galvanometer are

Options

A. plane surfaces of a bar magnetic
B. plane surfaces of a horse-shoe magnet
C. cylindrical surfaces of a bar magnet
D. cylindrical sufaces of a horse-shoe magnet

Answer

To solve the question regarding the pole pieces of the magnet used in a pivoted coil galvanometer, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Type of Magnet Used in Galvanometers**:
- Galvanometers typically use a horseshoe magnet due to its design, which provides a strong and uniform magnetic field.

2. **Eliminate Irrelevant Options**:
- The options include bar magnets and horseshoe magnets. Since we know that galvanometers use horseshoe magnets, we can eliminate options related to bar magnets.
- This leaves us with:
- Option B: Plane surfaces of a horseshoe magnet
- Option D: Cylindrical surface of a horseshoe magnet

3. **Understand the Shape of the Magnet**:
- The horseshoe magnet has a specific shape that allows for a more effective magnetic field. The cylindrical shape of the horseshoe magnet is designed to create a uniform magnetic field.

4. **Determine the Magnetic Field Characteristics**:
- In a pivoted coil galvanometer, a uniform radial magnetic field is desired. This is because it ensures that the plane of the coil remains parallel to the lines of magnetic force, allowing for accurate measurements.
- The cylindrical surface of the horseshoe magnet creates this uniform radial magnetic field.

5. **Conclude the Correct Option**:
- Based on the above reasoning, the correct answer is:
- **Option D: Cylindrical surface of a horseshoe magnet**.