Using a 4-band color code, what is the color code for a 100 Ω resistor with ±5% tolerance?

• A. Red-Black-Brown-Gold
• B. Brown-Gray-Black-Gold
• C. Brown-Black-Red-Gold
• D. Brown-Black-Brown-Gold

Answer: (D)

Resistor color bands encode the value as digits, a multiplier, and tolerance. The first two bands are the significant digits, the third is the multiplier (how many tens), and the fourth shows tolerance.

For 100 ohms, you want digits 1 and 0, which are brown and black. The multiplier must be 10 to turn 10 into 100, and the color for ×10 is brown. The tolerance of ±5% is indicated by gold. So the four-band color code is brown, black, brown, gold.

Other sequences would yield different values, such as brown-black-red-gold giving 1000 ohms, or red-black-brown-gold giving 200 ohms, so the brown-black-brown-gold combination specifically matches 100 Ω with ±5% tolerance.