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Connecting an ammeter to measure current

Aviation Mechanic General (AMG) practice question 14 of 41 on Fundamentals of Electricity and Electronics. ACS element AM.I.A.R1 · difficulty: standard. Want to answer it in a timed quiz? Use the Aviation Mechanic General (AMG) practice mode.

Question bank updated 2026-09-22

QUESTIONA mechanic wants to measure the current flowing through a lamp in a DC circuit. How must the ammeter be connected?

  1. AIn series, by breaking the circuit and inserting the meter
  2. BIn parallel across the lamp, the same way a voltmeter is connected
  3. CAcross the source terminals with the lamp disconnected from the circuit
Show the answer and explanation

Correct answer: A. In series, by breaking the circuit and inserting the meter

  • A — correct The handbook states that current is measured with the ammeter connected in the current path by opening or breaking the circuit and inserting the meter in series.
  • B — incorrect Parallel connection across a component is the method for measuring voltage, not current.
  • C — incorrect Connecting an ammeter directly across the source would not measure the lamp current and does not follow the series-insertion procedure.

BACKGROUND

Voltmeters and ammeters are connected differently even though both are basically current-measuring movements. A voltmeter is connected in parallel across the two points whose voltage is to be measured, using a high-resistance meter so it does not shunt significant current from the circuit. An ammeter is connected in the current path by opening or breaking the circuit and inserting the meter in series. Standard practice is to install the red lead in the positive jack and the black lead in the negative jack, with the positive side of the meter toward the positive voltage source. Because the ammeter's internal resistance is in series with the circuit, it is kept small so it has little effect on the reading.

STUDY TIP

Remember the rule pair: volts across (parallel), amps through (series).

KEY POINTS

  • An ammeter is inserted in series by breaking the circuit.
  • A voltmeter is connected in parallel across the component.
  • Observe polarity: red lead to positive, black lead to negative.

SOURCES

  • FAA-H-8083-30B ch12 "Current Measurement" and "Voltmeter Circuit Connections"
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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.