• 30/ 07, 2019

We come across myriads of electrical and electronic instruments in our everyday life. All of this equipment is made of circuits with the right connections for accurate functioning of these appliances. For a circuit to function well, a vital component called a resistor needs to be present. Resistors are one of the electrical essentials that should be there in all the appliance. A resistor controls the continuous flow of current, failing which there are chances of overheating and difficulty in controlling the current flow whenever required. For purchasing a resistor, you need a basic knowledge and understanding about resistor colour code. Wondering how to decode, fret not! Here is a simple and complete guide for you to understand how to read a resistor colour code.

Decoding the electric circuits

Resistors are inbuilt safety accessories while using an appliance. To comprehend details regarding the resistor colour code, it is important to understand specific terminologies. First in the list is resistance. As the name goes, resistance is a quantity that measures the restriction to the free flow of current in a circuit. The unit of measurement is ohms. Next is tolerance, which indicates the accuracy of the resistance value. Another term is temperature coefficient, which refers to the change in temperature with the change in resistance. A resistor colour code marks the values for the above three terms.

How to read resistor colour codes?

All resistors available in the market have a pattern of colour codes on it. You should always read the bands from left to right. Each of the bands indicates the following:

  • Resistance value
  • Tolerance
  • Temperature co-efficiency

Typically, a resistor can hold about three to six colour bands, of which the first few bands from the left is marked with digits depending on the colour. Next, you will find a band that signifies the multiplier, which indicates the decimal count. The last band on the right side is the value for tolerance and temperature coefficient.

There are multiple colours in in a resistor? Here is the list:

Colours in a resistor and value given to each colour.

The colours that code the resistors are black, brown, red, orange, yellow, green, blue, violet, grey and white. These colours are given numbers from 0 to 9 in the respective order. The digits from 0-9 mark resistance values.

The multiplier band is a single band which can be any colour from black to violet. But the values given to the band are in the form of 1, 10, 100, 1000 and so on. The remaining colour of list, grey and white do not signify any value when it comes to multiplier band. In addition to the colours listed, gold and silver mark values of 0.1 and 0.01 for a multiplier band. But gold and silver do not measure the resistance value.

Only a few colours denote the tolerance rating. Most frequently used colours are brown, red, gold and silver, which has the tolerance values of 1, 2, 5 and 10 percentage. Colours like green, blue, violet and grey indicate 0.5, 0.25, 0.1 and 0.05 percentage tolerance. These are rarely available. However, if your resistor has a tolerance of 2 per cent, then it shows it is a high precision resistor. When there is no band indicating tolerance, then the resistor assumes a default value of 20 per cent.

Sometimes, after the tolerance band, there might be a band denoting the temperature co-efficiency. The colours can vary between black, brown, red, orange, yellow, green, blue, violet and grey and the values held by these colours are 250, 100, 50, 15, 25, 20, 10, 5 and 1. Temperature co-efficiency has the unit of ppm/K.

Example to read a resistor colour code

It is natural for you to be confused with all the math mentioned above. But it is not as hard as you think. To make it easy for you to understand, we have used an example to get a clear picture. Imagine you have a resistor at hand that has four bands with the following colours, red, blue, brown and gold reading from left to right. Red and blue marks the digits 2 and 6. Brown is the multiplier band. Therefore you should multiply 26 with 10. Since gold is the last band, tolerance is 5 percent. Putting all the values together, you have your resistance value, which is 260 ohms with 5 percent tolerance.

Decide the right end in a resistor

Now that you have a better understanding of resister colour code, the next step is to comprehend which side is the left end in order to read the resister code right. This is one of the most common question that comes to mind when you look at a resistor. First, count the number of bands. It is easy to fix the right end band, as they are single bands denoting tolerance or temperature coefficient. Generally, the bands that are grouped towards the left end will signify the resistance and multiplier. Leaving a little gap, you will find the bands denoting tolerance. This will help you choose the direction for reading the bands correctly.

Uses of resistors

Resistors are virtually found in every electronic appliance. It is widely used in controlling the speed of a motor and sound of the amplifier. Say you want to control the flow of current to a device and you have a constant supply of voltage, resistors come handy for this purpose. Thus, it is generally referred to as circuit breakers. Resistors also play a vital role in heating appliances like a bulb, microwave, etc. When too much current flows through a LED light, resistors control the flow of current to keep the lights intact. These are just a few to mention. Resistors have a wide range of application in every electronic appliance.

Topics similar to resistors and electric wiring are not just restricted to physics textbooks and electricians but has a more extensive practical application in day to day activities. Getting to know about the resistor colour code enables you to buy the right product and gives you an understanding of the prevailing principles of the things that you handle every day. Head out to Finolex if you are looking for new electrical and electronic products.

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