If the magnetising field on a ferromagnetic material is increased, its permeability is

Options

A. decrease
B. increase
C. is unaffected
D. may be increase or decrease

Explanation

To solve the question regarding the relationship between the magnetizing field and the permeability of a ferromagnetic material, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Definitions**:
- The **magnetizing field (H)** is the external magnetic field applied to a material.
- The **magnetic permeability (μ)** of a material is a measure of how easily it can become magnetized when exposed to a magnetic field.

2. **Relationship Between Magnetic Field and Magnetizing Field**:
- The magnetic field (B) in a material can be expressed as:
\[ B = \mu H \]
- Here, \(B\) is the magnetic field, \(μ\) is the magnetic permeability, and \(H\) is the magnetizing field.

3. **Expressing Permeability**:
- We can rearrange the equation to express permeability as:
\[ \mu = \frac{B}{H} \]

4. **Analyzing the Effect of Increasing H**:
- If the magnetizing field \(H\) is increased, we need to analyze how this affects the permeability \(μ\).
- Since \(μ\) is defined as the ratio of \(B\) to \(H\), if \(H\) increases while \(B\) remains constant (which is often the case in ferromagnetic materials until saturation), the value of \(μ\) will decrease.

5. **Conclusion**:
- Therefore, we conclude that if the magnetizing field \(H\) is increased, the permeability \(μ\) of the ferromagnetic material decreases.

### Final Answer:
The permeability of the ferromagnetic material **decreases** when the magnetizing field is increased.

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