Class 11> Unit # 10: DC Circuits > Resistor Color Code

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Resistor Color Code

Resistor Color Coding

"The basis of this system is the use of colors for numerical values, summarizing the different weighted positions of each colored band which makes up the resistor's color code."

Carbon resistors are usually marked with colored bands around their body to indicate their resistance value and tolerance. In a standard 4-band resistor:

1. First Band: The band nearest to the lead gives the first significant digit.
2. Second Band: Marks the second significant digit.
3. Third Band: Serves as the multiplier, which determines the number of zeros to append after the first two digits (or the power of 10).
4. Fourth Band: Represents the tolerance, indicating the percentage accuracy or acceptable variation of the resistance value from its rated value.

Example Calculation (4-Band Resistor)

Consider a 4-band resistor with the following color stripes:

• First stripe (Brown): Digit 1
• Second stripe (Black): Digit 0
• Third stripe (Orange): Multiplier ($10^3$, meaning add 3 zeros to 10) $\rightarrow 10 \times 10^3\,\Omega = 10,000\,\Omega = 10\,\text{k}\Omega$.
• Fourth stripe (Gold): Tolerance of $\pm 5\%$.

Tolerance Range: With a 5% tolerance on $10\,\text{k}\Omega$, the actual resistance value lies between $9.5\,\text{k}\Omega$ and $10.5\,\text{k}\Omega$ ($10,000 \pm 500\,\Omega$).

If the fourth tolerance band is left blank, it results in a 3-band resistor. This means the resistance value calculated from the first three bands remains the same, but the default tolerance is $\pm 20\%$.

Fig: Standard 4-band carbon resistor showing digit bands, multiplier, and tolerance band.

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