SkyDrill

Retentivity of magnetic materials

Aviation Mechanic General (AMG) practice question 16 of 41 on Fundamentals of Electricity and Electronics. ACS element AM.I.A.K2 · difficulty: recall. Want to answer it in a timed quiz? Use the Aviation Mechanic General (AMG) practice mode.

Question bank updated 2026-09-22

QUESTIONThe ability of a magnet to hold its magnetism after the magnetizing force is removed is known as what?

  1. APermeability of the core material
  2. BRetentivity
  3. CMagnetic saturation
Show the answer and explanation

Correct answer: B. Retentivity

  • A — incorrect Permeability describes the ease with which magnetic flux can penetrate a material, not how well a material keeps its magnetism.
  • B — correct The handbook defines retentivity as the ability of a magnet to hold its magnetism, which varies greatly with the type of metal.
  • C — incorrect Saturation is the point reached during magnetic buildup after which there is no further increase, as in field saturation of a generator; it is not the property of holding magnetism.

BACKGROUND

Magnetism is the property of an object to attract certain metallic substances, chiefly ferrous materials such as soft iron, steel, and alnico. Different materials differ in how well they keep their magnetism once the external magnetizing force is removed; this property is called retentivity. Soft iron is very easily magnetized but quickly loses most of its magnetism when the magnetizing force is removed. The small amount that remains is called residual magnetism, and it is important in applications such as generator operation. Modern permanent magnets are made from special alloys such as alnico, ferrites, neodymium-iron-boron, and samarium-cobalt.

STUDY TIP

Learn the three terms retentivity, residual magnetism, and saturation as a set; the test likes to swap them.

KEY POINTS

  • Retentivity is a material's ability to hold its magnetism after the magnetizing force is removed.
  • Soft iron magnetizes easily but loses most of its magnetism quickly; what remains is residual magnetism.
  • Residual magnetism is important for generator operation.

SOURCES

  • FAA-H-8083-30B ch12 "Magnetism" (retentivity paragraph following "Types of Magnets")
Practice the Aviation Mechanic General (AMG) test →Timed 60-question exam, by ACS area, or review your misses. Free.
MORE ON FUNDAMENTALS OF ELECTRICITY AND ELECTRONICS

SkyDrill is not affiliated with the FAA. This is an original practice item based on FAA-H-8083-30B Aviation Maintenance Technician Handbook – General, 14 CFR part 43 and part 65. Regulations and handbooks are revised; confirm details against the current edition.