The phosphor bronze strip is used in a moving coil galvanometer because

Options

A. Its torsional constant is small
B. It is easily available
C. It is paramagnetic
D. it is diamagnetic

Answer

To answer the question "The phosphor bronze strip is used in a moving coil galvanometer because", we will analyze the properties of phosphor bronze and its relevance to the functioning of a moving coil galvanometer.

### Step-by-Step Solution:

1. **Understanding the Function of a Moving Coil Galvanometer**:
- A moving coil galvanometer is an instrument used to measure small electric currents. It consists of a coil of wire suspended in a magnetic field, and the deflection of the coil is proportional to the current flowing through it.

2. **Role of the Phosphor Bronze Strip**:
- The phosphor bronze strip serves as a suspension for the moving coil. It allows the coil to rotate freely while providing the necessary restoring torque.

3. **Properties of Phosphor Bronze**:
- **Non-Magnetic**: Phosphor bronze is non-magnetic, which means it does not interfere with the magnetic field in which the coil operates.
- **Low Torsional Constant**: It has a low torsional constant, which is crucial because it allows the coil to move easily in response to the current without requiring a large amount of force to return to its original position.
- **Resistance to Oxidation**: Phosphor bronze does not oxidize easily, ensuring durability and consistent performance over time.

4. **Evaluating the Options**:
- **Option 1**: Its torsional constant is small - This is correct. A low torsional constant is desirable for the sensitivity and accuracy of the galvanometer.
- **Option 2**: It is easily available - While this may be true, it is not the primary reason for its use in galvanometers.
- **Option 3**: It is paramagnetic - This is incorrect. Phosphor bronze is not paramagnetic.
- **Option 4**: It is diamagnetic - This is also incorrect. The relevant property is that it is non-magnetic.

5. **Conclusion**:
- The correct answer is that the phosphor bronze strip is used in a moving coil galvanometer because its torsional constant is small, allowing for better sensitivity and performance of the instrument.

### Final Answer:
The phosphor bronze strip is used in a moving coil galvanometer because its torsional constant is small.