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Finding resistance with Ohm's Law

Aviation Mechanic General (AMG) practice question 19 of 41 on Fundamentals of Electricity and Electronics. ACS element AM.I.A.K7b · difficulty: applied. Want to answer it in a timed quiz? Use the Aviation Mechanic General (AMG) practice mode.

Question bank updated 2026-09-22

QUESTIONA DC circuit has 24 volts applied and a measured current of 2 amperes. Using Ohm's Law, what is the resistance of the circuit?

  1. A48 ohms
  2. B0.083 ohm, the current divided by the voltage
  3. C12 ohms
Show the answer and explanation

Correct answer: C. 12 ohms

  • A — incorrect 48 is the product of 24 V and 2 A, which is the power in watts, not the resistance.
  • B — incorrect Resistance is found by dividing voltage by current, not current by voltage.
  • C — correct Ohm's Law rearranged for resistance is R = E/I; 24 V divided by 2 A equals 12 ohms.

BACKGROUND

Ohm's Law describes the relationship between voltage, current, and resistance. Its three equivalent forms are E = I(R), I = E/R, and R = E/I. The handbook shows a triangle with E above the line and I and R below it; covering the unknown quantity with a thumb reveals the operation to perform. To find R, cover R and the result shows that E is to be divided by I. One ohm of resistance limits the current to 1 ampere in a conductor to which 1 volt is applied.

STUDY TIP

Memorize the Ohm's Law triangle so you can transpose the formula quickly under time pressure.

KEY POINTS

  • R = E/I: resistance equals voltage divided by current.
  • 24 V / 2 A = 12 ohms.
  • Multiplying E by I gives power in watts, a common trap.

SOURCES

  • FAA-H-8083-30B ch12 "Ohm's Law" (Equation 3 and Figure 12-40 triangles)
Practice the Aviation Mechanic General (AMG) test →Timed 60-question exam, by ACS area, or review your misses. Free.
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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.