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Current limiter characteristics

Aviation Mechanic General (AMG) practice question 5 of 41 on Fundamentals of Electricity and Electronics. ACS element AM.I.A.K20 · difficulty: recall. Want to answer it in a timed quiz? Use the Aviation Mechanic General (AMG) practice mode.

Question bank updated 2026-09-22

QUESTIONWhat is a distinguishing feature of a current limiter compared with a fuse?

  1. AIt can be reset by hand after it opens, so it never needs replacement
  2. BIts copper link withstands a considerable overload for a short time
  3. CIts tin-and-bismuth strip melts instantly at any current above its rating
Show the answer and explanation

Correct answer: B. Its copper link withstands a considerable overload for a short time

  • A — incorrect Resetting is a feature of circuit breakers; once a current limiter opens it must be replaced.
  • B — correct The handbook states the current limiter link is usually made of copper and will stand a considerable overload for a short period of time.
  • C — incorrect The tin-and-bismuth strip describes most fuses, not the current limiter, whose link is usually copper.

BACKGROUND

Circuit protective devices protect the units and wires in a circuit by stopping current flow when it becomes greater than the wires can safely carry. In most fuses the strip of metal is an alloy of tin and bismuth that melts and opens the circuit when the current exceeds the fuse rating. The current limiter is very much like a fuse, but its link is usually made of copper and will stand a considerable overload for a short period of time; it opens in over-current conditions in heavy current circuits such as 30 amps or greater and is used primarily to sectionalize an aircraft circuit or bus. Once opened, a current limiter must be replaced. A circuit breaker, by contrast, can be reset, and automatic-reset breakers are not allowed in aircraft.

STUDY TIP

Sort the three devices by what happens after they open: fuse and current limiter are replaced, breaker is reset.

KEY POINTS

  • A current limiter has a copper link that tolerates a short overload.
  • It is used in heavy current circuits (30 amps or more) to sectionalize a bus.
  • Like a fuse, an opened current limiter must be replaced.

SOURCES

  • FAA-H-8083-30B ch12 "Current Limiter" (Circuit Protection Devices)
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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.