Retentivity measures what property?

• A. A measure of a materials ability to retain magnetism
• B. Dielectric strength
• C. Electrical conductivity
• D. Magnetic permeability

Answer: (A)

Retentivity describes how much magnetism a material retains after the external magnetizing field is removed. In other words, it is the residual magnetization a material holds when the applied field goes to zero, commonly called remanent magnetization or remanent flux density (B_r). This makes retentivity the measure of a material’s ability to keep magnetization once the magnetizing force disappears. Dielectric strength is about how much voltage a dielectric can withstand before breakdown, which has nothing to do with magnetism. Electrical conductivity is about how easily charges flow through a material, not how much magnetism remains. Magnetic permeability, on the other hand, describes how readily a material responds to an external magnetic field and becomes magnetized, not how much magnetization is left after the field is removed.