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Decoding a four-band resistor

Aviation Mechanic General (AMG) practice question 36 of 41 on Fundamentals of Electricity and Electronics. ACS element AM.I.A.K21 · 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 resistor marked with the end-to-center band system has bands of gray, blue, orange, and silver, read from the end toward the center. What is its rated value?

  1. A68,000 ohms, 10 percent tolerance
  2. B86,000 ohms, 10 percent tolerance
  3. C86,000 ohms, 5 percent tolerance, read from the silver band
Show the answer and explanation

Correct answer: B. 86,000 ohms, 10 percent tolerance

  • A — incorrect The band nearest the end gives the first digit; gray (8) is read before blue (6), so the digits are 8-6, not 6-8.
  • B — correct Gray is 8, blue is 6, orange adds three zeros, and a silver fourth band means 10 percent tolerance, giving 86,000 ohms plus or minus 10 percent.
  • C — incorrect A silver fourth band indicates 10 percent tolerance; 5 percent is indicated by a gold fourth band.

BACKGROUND

With the end-to-center band marking system, a resistor carries three or four color bands read from the end toward the center. The first band gives the first digit and the second band the second digit; neither is ever gold or silver. The third band gives the number of zeros to add, except that a gold third band means multiply the two digits by 10 percent and a silver third band means multiply by 1 percent. A fourth band, if present, gives the tolerance; if there is no fourth band the tolerance is 20 percent. The handbook example of gray, blue, orange, silver decodes to 86,000 ohms plus or minus 10 percent, with a maximum of 94,600 ohms and a minimum of 77,400 ohms.

STUDY TIP

Read from the band nearest the end, and remember that gold and silver never appear as the first two bands.

KEY POINTS

  • Bands 1 and 2 are digits, band 3 is the multiplier (number of zeros).
  • No fourth band means 20 percent tolerance.
  • Gray-blue-orange-silver = 86,000 ohms, 10 percent.

SOURCES

  • FAA-H-8083-30B ch12 "Color Band Decoding" (Figure 12-51 example)
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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.