Resistor Colour Codes

A resistor colour code was introduced in the year of 1920. These colour bands are printed on the body of tiny resistor components. For colour codes, we can employ the resistor mnemonic called BB ROY Great Britain Very Good Wife, where the beginning letter points to a unique colour.

All the electrical components and wires are coded with colours to identify their value and function. We use the following colours as tolerance codes on five bands only because of which the five-band resistors are called coloured tolerance bands:

• Red
• Brown
• Green
• Blue
• Violet

A resistor has many colour bands, where each band carries a specific purpose and function.

Tips for Reading the Resistor Codes

1. Check the manufacturer's documentation guide and make sure about the colour-coding system used.

2. If the resistance code seems doubtful, measure the resistance with the help of an ohmmeter. 

3. The first band is always closest to the lead and Gold-silver bands are always located at the last.

4.  Always read resistors from the left side to the right side. 

So, let's discuss the resistance colour code chart:

Resistor Colour Code Table

The table below shows the resistor colour codes:

Using the above chart, one can find that the following colours stand for the respective colour code.

As we discussed, each resistance colour code has a tolerance value. The tolerance value of the resistor is the % of error in the resistor's resistance. Also, Tolerance = value of resistor x value of tolerance band.

Let's see what are these:

Resistor Colour Code Calculator 

The below table shows the carbon resistor colour code:

The above chart describes everything we need to know about its value and tolerance. Here, each value has its own unique combination and identity.

Now, let's discuss the resistor colour coding formula:

Resistor Colour Coding Formula

For calculating the resistance colour code calculator, we need to group the values of the significant digits bands; it means we will take the values of the first two or three bands from the left, depending on the total number of bands, then we will multiply that value by the multiplier to get the resistance value of the resistor.

Let's suppose that we take a four-band resistor with the following band colours:

• Violet

• Green

• Yellow

• Gold

The first two colours in the four-band resistor, viz: violet and green indicate the significant digits (i.e., 75) which are according to the above table (a).

Now, we will multiply that number by the multiplier indicated with the third band, i.e., yellow and it has the value of 104 or 10000.

So the multiplication will be: 75 x 10000 = 750000 Ω

So, the minimum value is 750 k or 75 104 Ω.

The fourth band, i.e., gold indicates the tolerance of ±5% (as given in table a).

Now, to calculate the minimum and maximum resistance values, we need to multiply the resistance value by the tolerance percentage to obtain the following values:

Minimum = 750000 - (750000 x \[\frac{5}{100}\])

= 750000 - 37500 = 712500 = 712.5kΩ

Maximum = 750000+ (750000 x \[\frac{5}{100}\])

= 750000 + 37500 = 787500

So, the maximum value is 787.5kΩ

What is a Resistor?

We define a resistor as a passive two-terminal electrical component that is used as an electrical resistance viz: an element of the circuit. The unit of measurement of a resistor is 'ohm' and it is represented by the greek letter 'omega'. In electronic circuits, resistors are used to reduce the flow of current through the circuit and provide resistance to the flow of electric current in a circuit. , they are also used to perform the following operations:

• Adjust signal levels
• Divide voltages
• For biasing the active elements
• Terminate the transmission lines and many more places.

Uses of Resistors 

• They are used in devices that convert electrical energy into heat or other forms of energy.

• Used in conducting wires. 

• They are used in light bulbs to increase their lifespan and also to control temperature. 

• They are also used in loudspeakers and other electronic devices.

• They are also used in electric heaters, stoves, and ovens. 

Types of Resistors

There are two types of resistors; these are as follows:

1. Linear resistors

2. Nonlinear resistors

A. Resistors whose value varies with the change in the applied temperature and voltage are called linear resistors.  Linear Resistors are of two types, viz: fixed resistors and variable resistors, let’s discuss their types:

• Fixed Resistors

A fixed resistor has a fixed specific value that means its value cannot change whatever the conditions it is being subjected to. Fixed resistors are of the following types:

1. Carbon composition resistors

2. Wire wound resistors

3. Thick film resistors

Thick film resistors are of the following types:

a. Fusible resistors

b. Cermet film resistors

c. Metal oxide resistors

4. Thin-film resistors

Thin-film resistors are of the following types:

a. Carbon film resistors

b. Metal film resistors

• Variable Resistors:

The value of variable resistors can be varied with the help of a dial, knob, or screw. We can find their applications in radio receiving stations for controlling volume and tone. Variable resistors are of the following types:

1. Potentiometer

2. Rheostat

3. Trimmer resistors

B. Resistors whose value can vary according to the temperature or voltage applied to these; however, these resistors do not follow Ohm's law. Nonlinear resistors are of the following types:

• Thermistor

• Photoresistor LDR

• Varistor resistors

• Surface-mount resistors

Advantages of Resistors

• Resistors are cost-friendly. We can easily replace them without considering the cost. 

• Resistors are compact-sized. They can be carried from one place to another very easily. 

• They have easy and low maintenance. 

• They have a long lifespan and can handle environmental changes up to a limit. 

• They are easy to identify. 

• They can be used in temperature sensing, which makes them fit for many electronic devices. 

• It has a simple working principle.

• All the resistors have well-defined construction and can be applied to all the circuits easily.

Disadvantages of Resistors 

• In some cases, resistors dissipate heat. 

• The resistors may often get short-circuited because of another component in the circuit.

• Due to changes in thermal, electrical, or mechanical conditions, the resistance value can vary.

• They are not useful for applications that use power levels above 5 watts.

Zero-Ohm Resistors

The Zero-ohm resistors can be easily identified or recognized by their single black band. It is the wire link on the printed circuit board, with the only function of connecting traces. Zero-Ohm Resistor is also known as a zero-ohm link. The reason why these are made to look like resistors is that manufacturers can use them for placing components on a circuit board with the same automated machine. The zero-ohm resistor is used in reducing the cost of jumper wires insertion. 

Following are the Types of Resistors on the Basis of no. of Bands -

Three Band Resistors

In a three-band resistor, the third band represents the multiplier. A multiplier is a high resistance used to convert a galvanometer to a voltmeter. It also shifts the decimal place around to change the value from megaohms to milliohms and anywhere in between. It can be represented by the expression: AB × C ± 20%. 

Four Band Resistors

It is the most common and widely used resistor. Just like the three-band resistor, the first and second band represents the 1st and 2nd digit of the resistance value. The third band represents 'multiplier' and In the fourth band, it signifies tolerance. Sometimes, the 4 band resistor results in a three-band resistor if the tolerance band is left blank. In this case, the resistance will be the same but the tolerance would be ±20% (as if it were a 3 band resistor). It can be represented by the expression: AB × C ± D%

Five Band Resistor

The five band resistors have an extra band for a 3rd notable digit. Here, the first three bands represent the respective digits of the resistance. The fourth band is the multiplier and the fifth band is for tolerance. It can be represented by the expression: ABC × D ± E%.

Six Band Resistor

A six-band resistor is a 5 band resistor with an extra ring that denotes the temperature coefficient. Generally, 'brown' represents the sixth band (100 ppm/K) I.e, for every 10⁰C change in temperature, the resistance value changes by 0.1%. It can be represented by the expression: ABC × D ± E%, F. Here, 'F' is the sixth band.