Susceptibility is positive and small for a

Options

A. paramagnetic substances
B. ferromagnetic substances
C. non-magnetic substances
D. diamagnetic substances

Answer

To solve the question regarding the susceptibility of materials, we will analyze the properties of different types of magnetic materials.

### Step-by-Step Solution:

1. **Understanding Susceptibility**:
- Susceptibility (χ) is a measure of how much a material will become magnetized in an applied magnetic field. It can be positive or negative.
- Positive susceptibility indicates that the material is attracted to the magnetic field, while negative susceptibility indicates that the material is repelled.

2. **Types of Magnetic Materials**:
- **Paramagnetic Materials**: These materials have a small positive susceptibility. They are weakly attracted by a magnetic field and have a relative permeability (μ_r) slightly greater than 1.
- **Diamagnetic Materials**: These materials have a small negative susceptibility. They are weakly repelled by a magnetic field and have a relative permeability slightly less than 1.
- **Ferromagnetic Materials**: These materials have a large positive susceptibility and exhibit strong attraction to magnetic fields, often leading to permanent magnetism.
- **Non-Magnetic Materials**: These materials do not exhibit any magnetic properties and have a susceptibility close to zero.

3. **Analyzing the Given Options**:
- **Paramagnetic**: As discussed, they have a small positive susceptibility.
- **Ferromagnetic**: They have a large positive susceptibility, not small.
- **Non-Magnetic**: They have a susceptibility close to zero, not positive.
- **Diamagnetic**: They have a small negative susceptibility.

4. **Conclusion**:
- Since the question specifies that susceptibility is positive and small, the correct answer is **paramagnetic materials**.

### Final Answer:
The susceptibility is positive and small for **paramagnetic materials**.