Typical magnitude of relative permeability in ferromagnets What is a representative order of magnitude for the relative permeability μr of a ferromagnetic core material?

Introduction / Context:
Magnetic circuit design requires realistic μr values to estimate magnetizing currents and flux densities. Ferromagnets can concentrate flux far more than air, which is why cores are widely used in inductors and transformers.

Given Data / Assumptions:

• Soft ferromagnetic materials (e.g., silicon steel, ferrites) under moderate flux densities.
• Small-signal or initial permeability context.

Concept / Approach:

Relative permeability μr = μ/μ0 measures how much more permeable a material is than vacuum. Ferromagnets commonly exhibit μr from hundreds to many thousands depending on composition, processing, and frequency. Values well above 10^3 are routine for soft magnetic alloys at low frequencies before saturation effects reduce incremental permeability.

Step-by-Step Solution:

Verification / Alternative check:

Manufacturer datasheets for electrical steels and ferrites list initial μr in the thousands, confirming the typical magnitude.

Why Other Options Are Wrong:

A and B reflect non-ferromagnetic behavior; C underestimates by an order of magnitude; E is unrelated to μr values.

Common Pitfalls:

Confusing initial μr with differential μ at high B (which drops), or with complex μ at high frequency.

Final Answer:

1000 or more