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The three circuits of a high-tension magneto

Aviation Mechanic Powerplant (AMP) practice question 10 of 11 on Ignition and Starting Systems. ACS element AM.III.H.K4 · difficulty: recall. Want to answer it in a timed quiz? Use the Aviation Mechanic Powerplant (AMP) practice mode.

Question bank updated 2026-09-22

QUESTIONFor purposes of study, the high-tension magneto system is divided into which three circuits?

  1. AMagnetic, capacitive, and secondary electrical circuits
  2. BMagnetic, primary electrical, secondary electrical
  3. CPrimary electrical, secondary electrical, lead
Show the answer and explanation

Correct answer: B. Magnetic, primary electrical, secondary electrical

  • A — incorrect There is no separate capacitive circuit; the condenser is a component wired in parallel with the breaker points inside the primary circuit.
  • B — correct The handbook divides the high-tension magneto system into a magnetic circuit, a primary electrical circuit, and a secondary electrical circuit.
  • C — incorrect The ignition lead is part of the secondary circuit, and this grouping leaves out the magnetic circuit of rotating magnet, coil core, and pole shoes.

BACKGROUND

The magnetic circuit consists of a permanent multi-pole rotating magnet, a soft iron coil core, and pole shoes that carry the flux. The primary electrical circuit consists of a set of breaker contact points, a condenser wired in parallel with those points, and an insulated coil of a few turns of heavy copper wire. The secondary electrical circuit contains the secondary coil winding of roughly 13,000 turns of fine wire, the distributor rotor and block, the ignition lead, and the spark plug. Opening the breaker points at the E-gap position collapses the primary current and produces the rapid flux change that induces high voltage, often as high as 20,000 volts, in the secondary.

STUDY TIP

Memorize the trio as magnetic, primary, secondary, and be able to name one or two parts that live in each; questions often test membership rather than the list itself.

KEY POINTS

  • The three circuits are magnetic, primary electrical, and secondary electrical.
  • Breaker points and the condenser belong to the primary circuit.
  • The secondary coil, distributor, lead, and plug form the secondary circuit.

SOURCES

  • sources/amp-powerplant/ch04.txt "High-Tension Magneto System Theory of Operation"
  • sources/amp-powerplant/ch04.txt "Primary Electrical Circuit"
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SkyDrill is not affiliated with the FAA. This is an original practice item based on FAA-H-8083-32B Aviation Maintenance Technician Handbook – Powerplant, and 14 CFR part 43. Regulations and handbooks are revised; confirm details against the current edition.