Sunday, 26 January 2014

Resistors Color Coding

Resistors Color Coding
Carbon-composition and carbon film resistors are too small to have the resistance value printed on their housings. Therefore, bands of colour are used to represent the resistance value.

The first and second band represent the numerical value of the resistor, and the colour of the third band specify the power-of-ten multiplier. The colour bands are always read from left to right starting with the side that has a band closer to the edge.

For carbon-composition and carbon film resistors, the common tolerances are 5%, 10%, and 20%, indicating that the actual value of the resistor can vary from the nominal value by ±5%, ±10% and ±20%. If the band is gold, it specifies a 5% tolerance; silver specifies a 10% tolerance; if no band is present, the tolerance is 20%.

Note that the colour-code system for capacitors is very similar to that of resistors except there is a fifth band representing the temperature coefficient. This band is the first one closest to one end of the capacitor. The other four fall into the same order as mentioned for resistors. In this case, the second, third, and fourth bands are used to determine the capacitance. The fifth band represents the tolerance of the capacitor.

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