Electricity and Electronics — practice questions

16% of the exam ≈10 real questions 10 free questions here

The largest General subject in this site's weighting at 16%. Ohm's, Watt's and Kirchhoff's laws, series and parallel circuits, capacitance and inductance, transformers, batteries, circuit protection, semiconductors and digital logic. Most questions are short calculations where the distractors are the classic wrong operations.

Where people lose points

• Parallel resistance is always smaller than the smallest branch. If your answer is bigger, you added instead of using product-over-sum or reciprocals.
• Capacitors combine the opposite way from resistors: they ADD in parallel and use reciprocals in series.
• Inductive reactance rises with frequency (XL = 2πfL); capacitive reactance falls with it (XC = 1/2πfC).
• An ammeter goes in series, a voltmeter in parallel, and an ohmmeter only on a de-energized circuit.
• A circuit breaker or fuse is sized to protect the wire, not the load.

Questions and answers, explained

All 5 questions above, with the correct answer and why it is correct. Everything here is on electricity and electronics.

1. If the frequency applied to an inductor is doubled, its inductive reactance

   • AdoublesCorrect
   • Bis cut in half
   • Cstays the same
   • Ddrops to zero

   Why: XL = 2πfL, so inductive reactance is directly proportional to frequency: double the frequency, double the reactance. Capacitive reactance does the opposite.

   Reference AM.I.A.K4 · FAA-H-8083-30B, Ch. 12 (Inductive Reactance)

2. To measure the current through a load, an ammeter must be connected

   • Ain parallel with the load
   • Bin series with the loadCorrect
   • Cacross the battery terminals
   • Dbetween the load and ground, with power off

   Why: All of the circuit's current must pass through the ammeter, so it goes in series. A voltmeter goes in parallel. An ammeter placed in parallel, or across the battery, acts like a near-short and can be destroyed.

   Reference AM.I.A.K8 · FAA-H-8083-30B, Ch. 12 (Ammeters)

3. A hydrometer reading of 1.290 taken on a lead-acid aircraft battery at 80 °F indicates

   • Aa high state of chargeCorrect
   • Ba low state of charge
   • Ca fully discharged battery
   • Delectrolyte that needs a temperature correction

   Why: The FAA handbook gives 1.300 to 1.275 as a high state of charge, 1.275 to 1.240 as medium, and 1.240 to 1.200 as low. No temperature correction is needed between 70 °F and 90 °F, so 1.290 at 80 °F reads as high.

   Reference AM.I.A.K15 · FAA-H-8083-30B, Ch. 12 (Lead-Acid Battery Testing Methods)

4. The basic function of a diode is to

   • Astore a charge between two plates
   • Bamplify a weak input signal
   • Clet current flow in one direction onlyCorrect
   • Dstep AC voltage up or down

   Why: A diode conducts when forward biased and blocks current when reverse biased, which is why diodes are used as rectifiers to change AC into DC. Storing charge is a capacitor; amplifying is a transistor.

   Reference AM.I.A.K21 · FAA-H-8083-30B, Ch. 12 (Semiconductor Diodes)

5. Before handling an electrostatic-discharge-sensitive circuit card, a technician should

   • Awipe the card with a dry cloth to remove charge
   • Bwear a grounded wrist strapCorrect
   • Chold the card by its connector pins
   • Dstore it in an ordinary plastic bag

   Why: A grounded wrist strap bleeds static charge from your body before it can arc into sensitive components. Rubbing with a dry cloth or ordinary plastic builds static; handling by the pins puts any discharge right into the circuitry. Use conductive packaging.

   Reference AM.I.A.K24 · FAA-H-8083-30B, Ch. 12 (Electrostatic Discharge)

Topics inside this domain

• A&P General: Ohm's law, power and series-parallel circuits

Drill other domains

• Aircraft Drawings (4%)
• Weight and Balance (6%)
• Fluid Lines and Fittings (4%)
• Materials, Hardware and Processes (8%)
• Ground Operations and Servicing (9%)
• Cleaning, Corrosion and Finishes (14%)

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