When a small magnetising field H is applied to a magnetic material the intensity of magnetisation (I) is proportional to:

A. `H^(-2)`
B. `H^(1//2)`
C. H
D. `H^2`

Options

A. `H^(-2)`
B. `H^(1//2)`
C. H
D. `H^(2)`

Answer

To solve the question, we need to determine how the intensity of magnetization (I) is related to the magnetizing field (H) when a small magnetizing field is applied to a magnetic material.

### Step-by-Step Solution:

1. **Understanding Intensity of Magnetization (I)**:
- The intensity of magnetization (I) is defined as the magnetic moment per unit volume of the material.
- Mathematically, it can be expressed as:
\[ I = \frac{M}{V} \]
where \(M\) is the magnetic moment and \(V\) is the volume.

2. **Magnetic Susceptibility (χ)**:
- Magnetic susceptibility (χ) is a dimensionless quantity that indicates how much a material will become magnetized in an applied magnetic field.
- It is defined as:
\[ \chi = \frac{I}{H} \]
Rearranging this gives:
\[ I = \chi \cdot H \]

3. **Proportional Relationship**:
- For small magnetizing fields, the magnetic susceptibility (χ) is typically considered to be a constant for a given material.
- Therefore, we can express the relationship between I and H as:
\[ I \propto H \]
This indicates that the intensity of magnetization (I) is directly proportional to the magnetizing field (H).

4. **Conclusion**:
- From the above analysis, we can conclude that when a small magnetizing field H is applied to a magnetic material, the intensity of magnetization (I) is proportional to \(H\).
- Thus, the correct answer to the question is **C. H**.