Magnetic permeability is maximum for

Options

A. ferromagnetic substances
B. diamagnetic substances
C. paramagnetic substances
D. all of these

Explanation

To determine for which type of material the magnetic permeability is maximum, we can follow these steps:

### Step-by-Step Solution:

1. **Understand Magnetic Permeability**:
- Magnetic permeability (μ) is a measure of how well a material can support the formation of a magnetic field within itself. It indicates the ability of a material to become magnetized when exposed to an external magnetic field.

2. **Identify Types of Magnetic Materials**:
- There are three main types of magnetic materials:
- **Diamagnetic**: Materials that have a very weak negative susceptibility to magnetic fields (e.g., copper, bismuth).
- **Paramagnetic**: Materials that have a weak positive susceptibility to magnetic fields (e.g., aluminum, platinum).
- **Ferromagnetic**: Materials that have a strong positive susceptibility to magnetic fields and can retain magnetization (e.g., iron, cobalt, nickel).

3. **Compare Susceptibility**:
- The magnetic susceptibility (χ) of these materials varies significantly:
- **Diamagnetic**: χ is very low (negative).
- **Paramagnetic**: χ is low but positive.
- **Ferromagnetic**: χ is very high (positive).

4. **Relate Susceptibility to Permeability**:
- The relationship between magnetic permeability (μ) and magnetic susceptibility (χ) is given by the formula:
\[ μ = μ_0 (1 + χ) \]
where \(μ_0\) is the permeability of free space.
- Since ferromagnetic materials have the highest susceptibility, they will also have the highest permeability.

5. **Conclusion**:
- Based on the above analysis, we conclude that magnetic permeability is maximum for **ferromagnetic substances**.

### Final Answer:
Magnetic permeability is maximum for **ferromagnetic substances**.

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