Resistor Colour Code And Its Application

Resistors offer resistance to the current flow. They are two passive terminal devices used in electrical or electronic circuits to limit the current, for voltage division and for many other uses. In Class 12 NCERT Physics Chapter on Current Electricity there are topics related to resistance and resistors, among them is resistance colour code.

Students learn the resistance colour code and answer questions based on the resistor colour coding. Apart from learning the theory and writing the exam many students may have the doubt that why should I learn this. The reason is, resistors may be used in labs or in simple circuits while performing activities or doing projects. The students who are interested in playing with electric circuits may be aware of the use of resistor colour code. Still there will be students who may not be aware of what is the use of learning resistor colour coding. Let us see how the topic resistor colour coding is helpful practically.

Application Of Resistor In Electronic Circuits

Let us see a simple example

A resistor is required in the led circuit to limit current and protect the LED from burning. If you directly connect it to a battery of say 9V the chance of the LED burning is high. Suppose you find out that the resistance required is 1000 ohms to protect the led. You go to an electronic shop and ask for a resistor of 1000 ohm. But, how can you verify the given resistance is 1000 ohm? A simple way is to see the resistor colour band and verify that the given resistance is of 1000 ohm or 1 kilo ohm. This is where the resistors' use of colour coding comes into play. That is, in the design of electrical circuits the resistor value plays an important role. One can verify the value of the resistor by looking at the colour band. Also resistor power rating should be considered while designing circuits and purchasing the resistor. There are various resistor types available. For small voltage portable circuits the resistor with colour codes are used. If you repair a TV remote you can see the resistor in it with colour code..

Let us see what would be the resistor colour code for a 1000 ohm resistor with a tolerance of five per cent. For this first we have to know the concept of colour coding. Let's have a brief look at resistor colour coding. For more information refer to NCERT book for Class 12 Physics.

Resistor Colour Code Table

Tolerance is usually represented by Gold, Silver and No Colour

ToleranceValue Of Resistors

The first two colours represent significant figures, third colour represents multiplier and fourth colour the tolerance.

So the 1000 Ohm resistor with five per cent tolerance will have a colour code of Brown, Black, Red and Gold

Brown represents 1, black represents zero. So the significant figure is 10.

Red represent multiplier 102

So the value of the resistor is 10 x 102=1000 Ohm. And gold represents tolerance.

So the given resistor is 1000 Ohm 5%. This is how the resistance value can be calculated using the colour code.

Students may have a doubt from where should I start reading the colour band. If the above figure is rotated by 180 degrees then the band starts with gold. The basic thing to understand is always keep the metallic band to the right and start reading from the left. Now you can read it as brown, black, red and gold. If the resistor has no fourth colour then the tolerance is plus or minus 20 per cent.

You can try solving different resistor colour codes using the table. Memorise the table of colour code using some mnemonics, this will help in exams as well as while purchasing a resistor.