Colour Code (idea)

Resistors may use coloured bands to indicate their resistance value. This is called the resistor colour code. For a common four-band resistor: Band 1 → first significant digit. Band 2 → second significant digit. Band 3 → multiplier. Band 4 → tolerance.

Black → 0 Brown → 1 Red → 2 Orange → 3 Yellow → 4 Green → 5 Blue → 6 Violet → 7 Grey → 8 White → 9

Suppose the bands are: Red — Violet — Brown — Gold Red = 2. Violet = 7. Brown multiplier = ×10. So: **27 × 10 = 270 Ω Gold commonly represents: ±5% tolerance Therefore: 270 Ω ±5%**

Tolerance tells us the permitted variation around the marked resistance. A real resistor does not have to be exactly equal to its nominal value.