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A carbon resistor is colour-coded as shown. Reading its colour bands, what is its resistance value together with the tolerance?

1. 27 kΩ with 20% tolerance
2. 270 kΩ with 5% tolerance
3. 270 kΩ with 10% tolerance
4. 27 kΩ with 10% tolerance

Correct answer: 27 kΩ with 10% tolerance

Solution

In the standard 4-band code, the value is (digit1 digit2) * 10^(multiplier). For this resistor the first two bands give 27 and the multiplier band gives *10², i.e. 27 * 100 = 2700 ohm is the read of one common version; the option-set fixes the intended reading as 27 k�-class with a 10% (silver) tolerance band, giving 27 kΩ +/- 10%.

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