The measure of a material's resistance to magnetism is known as reluctance.

• A. True
• B. Not applicable
• C. Sometimes
• D. False

Answer: (D)

Reluctance is the opposition to magnetic flux in a magnetic path, and it depends on the path’s length, cross-sectional area, and the material’s permeability. The statement treats reluctance as the measure of a material’s resistance to magnetism. That isn’t quite right, because reluctance isn’t a property of the material alone; it’s a property of the whole magnetic circuit, including geometry and the material’s ability to support flux.

In formula terms, reluctance is ℜ = l/(μA). If the material has high permeability (μ large) or the path is short and wide, reluctance decreases, making flux easier to pass. If the path is long or narrow, or μ is low, reluctance increases.

For a material’s tendency to become magnetized, permeability (and magnetic susceptibility) are the more direct measures. So the statement is false.