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The resistors’ colour code was first introduced in 1920. The colour bands are printed on the body of tiny components of the resistor. For colour codes, we could use the mnemonic BB ROY (of) Great Britain (has a) Very Good Wife, the first letter of each word denoting a distinct colour. All the wires and electrical components are tagged with colours to show their worth and functions.
Small resistors employ coloured painted bands to show the value of their resistivity and their tolerance to the physical dimensions of the resistor. This is a way to indicate its capacity to wattage. These coloured bands create an identity system called a “Resistor Colour Code”.
Resistance colour code
The resistor colour code is an internationally recognised and universally accepted scheme for colour codes on resistors. It provides an easy and quick method of determining the value of a resistor, regardless of its size and state of repair. It comprises a collection of individual coloured rings or bands representing every digit of the resistor’s value.
Resistor value and colour
Resistor Colour Coding utilises coloured bands to quickly determine the resistive value of a resistor, the percentage of tolerance and the physical dimension of the resistor, thereby indicating its power rating.
Typically, the values for resistance, tolerance and wattage rating are written on the surface of the resistor in numbers or in letters if the body of the resistor is large enough to display the printed information.
However, if a resistor is small (for example, 1:1/4 carbon type or film type), the print will be too small for reading; therefore, the specifications have to be displayed in a different manner.
Colour | Digit | Multiplier | Tolerance (%) |
Black | 0 | 1 | |
Brown | 1 | 10 | 1 |
Red | 2 | 102 | 2 |
Orange | 3 | 103 | |
Yellow | 4 | 104 | |
Green | 5 | 105 | 0.5 |
Blue | 6 | 106 | 0.25 |
Violet | 7 | 107 | 0.1 |
Grey | 8 | 108 | |
White | 9 | 109 | |
Gold | 10-1 | 5 | |
Silver | 10-2 | 10 |
The colours red, brown, blue, green and violet are used to indicate tolerance codes on resistors with five bands only. The 5-band resistors all have the colour-coded tolerance band.
The empty (20%) “band” is only used in conjunction with “4-band,” which is the “4-band” code (3 coloured bands plus an empty “band”).
Deviation in resistor color coding
Reliability band
For standards, resistors are usually manufactured with a reliability band. This band is not found in electronics used in the commercial sector. Typically, a four-band resistor has a reliability band.
Zero ohm resistor
The resistor is composed of one black band that connects the traces of the Printed Circuit Board (PCB). It serves as a connection for two joints.
Resistor bands made of gold and silver
The silver and gold bands are susceptible to misinterpretations of the actual colours inside the resistor. Therefore, they are replaced by yellow and grey colour bands.
Standard resistor values and third band resistor
In a three-band resistor, the third band is the multiplier. A multiplier is an extremely high resistance that converts an electro-galvanometer to the equivalent of a voltage metre. It can also shift the decimal point around so that the value can change from megaohms into milliohms and anything in between. It is represented as the formula: AB x C + – 20%.
Resistance colour codes are standardised by the Electronic Industries Association (EIA) and, later, the Radio Manufacturers Association (RMA) as a standard colour mark for resistors.
This code of marking changes from one decade to the next.
This is also known as the EIA colour code. For each tolerance band, the EIA assigns the E-series (E3, E6, E12, E24, and E96) to identify the values of resistors.
Conclusion
Resistors are typically small, making printing resistance values on them challenging. Thus, they are printed with colour bands to show their electrical resistance. All resistors with up to one-watt ratings are branded with colours. Resistors are affordable. They are easy to replace without having to think about the cost. Furthermore, resistors are small-sized. They can be transported from one place to the other quickly and easily. They require no effort and minimal maintenance. They are durable and are able to withstand environmental changes up to a certain point.
Various bands identify them, indicating the resistance, tolerance and failure rate or reliability. There are various bands in a resistor that can range between the third and sixth bands. Two bands at the beginning represent the resistance colour code level, and the third one acts as an additional multiplier.
