Retentivity is defined as the ability of a magnetized metal to do what?

• A. Stay magnetized when the external magnetic field is removed
• B. Become magnetized in the presence of a field
• C. Demagnetize quickly when heated
• D. Repel other magnets with the same pole

Answer: (A)

Retentivity is the material’s ability to keep its magnetization after the external magnetic field is removed. When a ferromagnetic material is magnetized, its magnetic domains align. If a large portion of those domains remains aligned even after you remove the field, the material retains a magnetic field—that is high retentivity. This is what makes a permanent magnet hold its magnetization over time.

The correct description fits this idea: the material stays magnetized when the external field is removed. The other ideas describe different magnetic properties: magnetization that only appears in the presence of a field is about induced magnetization or magnetic susceptibility, not retention; demagnetizing quickly when heated points to thermal effects like reaching the Curie temperature, which is about losing magnetism due to heat, not retention; and repelling magnets with the same pole is about magnetic force interactions, not the ability to hold magnetization.