Which combination describes steel's magnetic properties?

• A. Low retentivity and high permeability
• B. High permeability and low retentivity
• C. Low reluctance
• D. High retentivity and low permeability and high reluctance

Answer: (D)

Soft magnetic materials like steel used in electrical equipment are chosen for their ability to carry magnetic flux easily while not remembering recent magnetization. This means they have high permeability, so magnetic flux passes through them with little opposition, and low retentivity, so they don’t stay magnetized when the exciting field is removed. Reluctance is the flip side of permeability: higher permeability gives lower reluctance, making it easier for flux to flow.

So the best description is high permeability with low retentivity. A material that retains magnetization (high retentivity) and, at the same time, resists flux (low permeability) would not behave like soft steel used in cores. Hard magnetic behavior would be described by high retentivity and high reluctance, which isn't typical for steel in electrical practice.