Understanding Resistor Colour Code And Tolerance

Resistors are passive electrical/electonics components that alters the flow of electric current in an electrical circuit. It works base on Ohms Law

Image credit: Khanacademy

Colour Codes are bands of colour printed upon resistor as a representation of its magnitude of resistance, tolerance and temperature coefficient
Colour codes can be in four band(four colours), five band or six band. Four colour band resistors are very common, Five colour band resistors are relatively available while six colour band resistors are rare to see
There are total of ten differnt colors use in colour codes, the first eight colour counting from zero are the colours atrributed to the resistance of the resistor while the last two colour represents the tolerance .
The chart for four colour band is shown in the image below

Four Colour Band Resistors
Four Colour band resistors are resistors which have only four colors printed upon it as a description of its magnitude of resistance and tolerance

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Example 1
What is the resistance, tolerance and range of resistances of the resistor below
image credit: khanacademy
Solution
First Step: Identify the colour that will come first. This can be done in two ways:

1. Taking the silver/Gold color as the last color(meaning the color at the opposite end of the silver/Gold colour is the first)
   2.Look at the two first colours at each end. Compare their proximity to each other, the colour nearer to the next color immediately after it will be taken as the first colour value. In the case of the given resistor, we have Orange and Orange at the top end and Silver and Brown at the lower end, if we compare their proximity, we would see that color orange and orange is closer to each other than colour Gold and Brown at the lower end. Therefore Orange colour becomes the first colour to choose

Second Step: Write down the corresponding values of the colors, then multiply by the multiplier that corresponds with the given colour
The colors of the given resistor are (Orange = 3, Orange = 3)*(Brown = 10^2) and Gold
a.The Resistance
33 * 10^2 = 3300Ω=3.3KΩ
b.Tolerance
Gold = 5%
c. Range Of resistances
3.3KΩ ±5%
5% = 5/100 * 3.3KΩ = 0.165KΩ
So, the range of values of resistance of the resistor is 3.3KΩ ±0.165KΩ =(3.3-0.165)KΩ to (3.2+0.165)KΩ
Range is from 3.135KΩ to 3.465KΩ

Example 2
For the Resitor below, find its
a. Resistance
b. Tolerance
c. Range of resistances

Image credit: Zseries
Solution
a. Resistance
Brown = 1
Black = 0
Blue(multiplier)= 10^6
10*10^6 = 10,000000 = 10MΩ
b. Tolerance
Gold = 5%
c. Range of values
10MΩ±5%
5% of 10MΩ = 5/100 * 10MΩ
= 0.5MΩ

So range of values = 10MΩ ±0.5 MΩ
∴ range of values is from 9.5MΩ to 10.5MΩ

Example 3
The resitance of a resitor is 27Ω and is tolerance is 10%, represent this resistor in a four colour band
Solution
Resistance = 27Ω
the color that corresponds to 2 in the chart is Red, similary 7 is Violet
a careful look will show that the 27Ω is multiplied by 1 since there must be a multiplier
from indices 1= 10^0. From the color chart, we see that color Black has a multiplier of 10^0
Tolerance of 10% corresponds to Silver color in the color chart
Therefore, the color code of the resistor is Red Violet Back and Silver

Five Colour Band Resistors

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Example 4
For the resistor shown in the below image. Find :
a. Resistance of the resistor
b.Tolerance
c. Range of resistances of the resistor

Solution

NB: How to determine the colour that will come first has been explained in example 1

a. Resistance
Orange = 3
Orange = 3
White = 9
Black(multiplier) = 10^0
Resistance = 339*10= 3390Ω = 3.39KΩ
b. Tolerance
Brown = 1% Tolerance
c. Range of resistance
*3.39KΩ ±1%
*1% of 3.39KΩ = 1/100 * 3.39
= 0.0339KΩ
*so the range of resistances of the resistor is from (3.39KΩ- 0.039KΩ) to (3.39KΩ + 0.039KΩ)

Example 5
What will be the colour code in five band of a resistor of resistance 470KΩ and tolerance of 10%
Solution
4 =Yellow
7 = Violet
0 = Black
10^3 (K) =Orange(Multiplier)
Silver = 10% Tolerance
So, the color code of the resistor is _Yellow, Violet, Black, Orange and Silver*.

Six Colour Band Resistors

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Six colour band resistors are similar to five color band resistors. In six color band resistors, we take the first five colors as the resistance and tolerance of the resistor just as in five colour band resistors and take the last colour which is the sixth as temperature coefficient

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Below are some exercises to test your understanding. Feel free to ask any question

Exercise

1. What is the resistance, tolerance and range of resistances of the resistor shown in the image below
   
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2. A resistor has Red, yellow green and brown as its colour code. What is the resistance, tolerance and range of resistances of the resistor
3. The resistance of a five colour band resistor is 470KΩ and its tolerance is 10%. What is the color code of this resistor
4. A six colour band resistor has Blue, Green, Orange,Violet,Silver and Blue as its colour code. Find the resistance, tolerance range of resistances and temperature coefficient of the resistor

All the written examples and exercises are from my intellect. The images are as credited. I personally calculated every example on this article. You can follow me @ikchris

References
.Physics And Radio Electronics
.Electrical Classroom