Which of the following are the three basic properties of magnetism?

• A. Permeability, reluctance, remanence
• B. Permeability, reluctance, retentivity
• C. Permeability, reluctance, retentivity
• D. Permeability, reluctance, resistivity

Answer: (C)

Permeability, reluctance, and retentivity describe how a material behaves in a magnetic field. Permeability is how easily magnetic flux can pass through the material—the higher the permeability, the less the material resists the flow of flux. Reluctance is the opposite concept, a measure of how strongly the material opposes the creation of magnetic flux, depending on both the material and its shape. Retentivity, or retentivity in this sense, is the material’s ability to stay magnetized after the external magnetizing field is removed, which is why some materials remain magnetized (hard magnets) while others demagnetize quickly (soft magnets).

Resistivity, on the other hand, concerns how a material conducts electricity and is not a magnetic property, so it isn’t part of the three basic magnetic properties.