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# 2.2 Analogue electronics. Resistors (6). Color codes

Components and wires are coded with colors to identify their value and function.

Manufacturers of the resistors cannot guarantee the exact value. The fourth band expresses the TOLERANCE in %. With the tolerance we can calculate the minimum and maximum real values for the four resistors below as in the example:

Red /violet / orange //silver
R =27000 Ω ±10%
10% of 27000 = 27000·10/100=2700
R = 27000 Ω ± 2700 Ω
Minimum value =27000-270=26730 Ω
Maximum value = 27000+270=27270

Exercise 20. Fill in the blanks

A lot of resistors have coloured rings on them instead of numbers. Each colour stands for a different unit: black is zero, brown is ____, red is two; orange is three; yellow is _____; green is five; ____ is six; violet is seven; grey is _____; white is nine, as you can see in the table below.
The first band is for tens and the second band for units. The third band is the multiplier.

Example: red / violet / green stands for 2 / 7 / 00000, that is 2700000 Ω or 2.7 MΩ.

Exercise 21. Obtain the value of these resistors:
a) Brown / green / red:
b) Orange / orange / brown:
c) Green / grey / yellow:
d) Yellow /violet / orange:

Express the previous values with M or k if possible. For example 27000 Ω = 27 kΩ

Exercise 22. Obtain the value and the tolerance of these resistors

 Colours Value Tolerance (%) Tolerance Minimum value Maximun value Red /violet / orange //silver 27000 Ω 10% 2700 26730 Ω 27270 Ω Brown / green / red // silver Orange / orange / brown // gold Green / grey / yellow // silver Yellow /violet / orange // gold

Exercise 23. Work with your partner in turns. Choose 1 resistor from the pool and write down its colours. Then you have to tell your partner the colours and he has to find out the value.

 1kΩ                 120Ω                                                       1.5 kΩ                                                                              1.2 kΩ                                                           1.8 MΩ           18 Ω                                   2200 Ω                                              820 Ω                                                                        270 kΩ                                                           270 Ω  3.3 MΩ                         330 kΩ                           390 Ω                                                          4700 kΩ                                                          47 kΩ                                                5.6 kΩ

It would be someting like this:

- My resistor is brown, black, red.

- Is it 1000 Ω?

- Yes, it is. You are right…

Exercise 24. Your teacher will give you one real resistor. Note down the colours, calculate its value and write the text to describe your resistor to the class.

The first band colour of my resistor is......
The quoted value is ..........................
The tolerance is...
The minimum…

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