The magnetic permeability value for iron (specifically 99.95% pure Fe annealed in H) is 2.5 × 10⁻¹ H/m.
Understanding Magnetic Permeability of Iron
Magnetic permeability (μ) is a measure of a material's ability to support the formation of a magnetic field within itself. In simpler terms, it indicates how easily a material can be magnetized or how well it can conduct magnetic lines of flux. The higher the permeability, the more easily the material can concentrate magnetic fields.
Iron is a ferromagnetic material, known for its high permeability, making it very effective for applications requiring strong magnetic responses, such as in electromagnets, transformer cores, and magnetic shielding. The specific value can vary depending on the iron's purity, its crystalline structure, and how it has been processed (e.g., annealing).
The provided reference highlights the permeability for a specific type of iron:
| Material | Relative Permeability, max. , μ/μ₀ | Permeability, μ (H/m) |
|---|---|---|
| Iron (99.95% pure Fe annealed in H) | 200,000 | 2.5 × 10⁻¹ |
| Permalloy | 100,000 | 1.25 × 10⁻¹ |
| NANOPERM® | 80,000 | 1.0 × 10⁻¹ |
| Mu-metal | 50,000 | 6.3 × 10⁻² |
As seen in the table from Wikipedia's Permeability (electromagnetism) article, pure iron annealed in hydrogen exhibits a very high maximum relative permeability of 200,000 and an absolute permeability of 2.5 × 10⁻¹ H/m. This high value indicates its excellent magnetic properties.
Key Aspects of Iron's Permeability:
- Purity and Processing: The permeability value is highly dependent on the iron's purity and its heat treatment. For instance, 99.95% pure Fe annealed in H refers to a highly purified form of iron that has undergone annealing in a hydrogen atmosphere, a process known to enhance its magnetic properties by reducing impurities and internal stresses.
- Units: Permeability is measured in Henries per meter (H/m) in the SI system.
- Relative Permeability (μr): This is the ratio of a material's absolute permeability (μ) to the permeability of free space (μ₀, approximately 4π × 10⁻⁷ H/m). A high relative permeability, like 200,000 for pure iron, signifies its strong magnetic response compared to a vacuum.
Understanding iron's magnetic permeability is crucial for engineers and scientists in fields like electrical engineering, materials science, and physics, as it directly impacts the design and performance of various magnetic devices.
