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Statement of Faraday's Law

Aviation Mechanic General (AMG) practice question 31 of 41 on Fundamentals of Electricity and Electronics. ACS element AM.I.A.K7e · difficulty: recall. Want to answer it in a timed quiz? Use the Aviation Mechanic General (AMG) practice mode.

Question bank updated 2026-09-22

QUESTIONAccording to Faraday's Law of electromagnetic induction, the emf induced in a closed loop of wire is proportional to what?

  1. AThe resistance of the wire making up the coil
  2. BThe steady strength of a stationary magnet placed inside the coil
  3. CThe rate of change of magnetic flux through the coil
Show the answer and explanation

Correct answer: C. The rate of change of magnetic flux through the coil

  • A — incorrect Resistance affects how much current the induced emf can drive, but it is not what determines the magnitude of the induced emf.
  • B — incorrect A magnet at rest inside a coil induces no voltage; the handbook shows the galvanometer reads zero when the magnet is stationary. Only a changing field induces emf.
  • C — correct Faraday's Law states that the induced emf in a closed loop of wire is proportional to the rate of change of the magnetic flux through the coil.

BACKGROUND

Michael Faraday discovered in 1831 that moving a magnet through a coil of wire induces a voltage across the coil, and if a complete circuit is provided a current also flows. The amount of induced voltage is directly proportional to the rate of change of the magnetic field with respect to the coil. This is known as Faraday's Law, or the Law of Electromagnetic Induction. When the magnet is at rest inside the coil, no voltage is induced and a galvanometer connected to the coil reads zero.

STUDY TIP

Key word is change: a magnetic field must be changing relative to the coil to induce an emf.

KEY POINTS

  • Faraday's Law: induced emf is proportional to the rate of change of magnetic flux.
  • A stationary magnet in a coil induces nothing.
  • A complete circuit turns the induced emf into induced current.

SOURCES

  • FAA-H-8083-30B ch12 "Characteristics of Inductance"; "Generator Principles"
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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.