On this page we are going to look at is the resistor. Its a very common in electronics circuits. We are going to start with a picture and a table showing how we can work out the Resistance value. I have kept these together to make it easier to use. The description will come after.
Resistor Colour codes
|1st Digit||2nd Digit||Multiplier||Tolerance|
|0 Black||0 Black||0.01 Silver||+/- 10 % Silver|
|1 Brown||1 Brown||0.1 gold||+/- 5 % Gold|
|2 Red||2 Red||1 Black||+/- 1% Brown|
|3 Orange||3 Orange||10 Brown||+/- 2 % Red|
|4 Yellow||4 Yellow||100 Red|
|5 Green||5 Green||1000 Orange|
|6 Blue||6 Blue||10,000 Yellow|
|7 Purple||7 Purple||100,000 Green||+/- 0.5 % Green|
|8 Grey||8 Grey||1,000,000 Blue||+/- 0.25 % Blue|
|9 White||9 White||10,000,000 Purple||+/- 0.1 % Purple|
The image shows a 4 band resistor, its the most common but you can also get 5 and 6 band’s. The first two bands give us numbers. On the resistor above the first one is brown, which is 1. The second is black which is 0. So we have 10. The third band is yellow. This band is a multiplier. in this case its 10,000. So we have 10 multiplied by 10,000 giving us 100,000. In electronics we use the standard units. So we shorten this to 100 K. The K means thousand. The last band is gold. Which gives us a tolerance of 5 %.
Now we have had a chance to look at a resistor and a table showing some values. We need to look at what it is, what it does and how to use it.
What is a Resistor ?
The above image shows the inner workings of a Carbon Film resistor. It is a common type of resistor but there are other types. At both ends we have the leads. This is where we connect the resistor to the rest of the circuit. The resistor consists of a small insulating ceramic rod wrapped with carbon film. The Carbon film length, width and number of turns affect the resistance. So they are carefully constructed. The whole resistor is wrapped in an insulating coating. Which stops short circuits.
What does a Resistor do ?
A resistor is used to control the flow of Current in a circuit. As the name suggests, it ” resists ” the flow of current. The larger the resistance, the more limits the current. It does this by converting the energy to heat. The heat is then transferred to the surrounding air. Unfortunately the heat can only transfer so fast. If the value of a resistor is picked poorly, it may heat up too fast and fail.
Resistors are often used to protect other components, one very common use is to limit the current flowing to Light Emitting Diodes. ( LED’s ) Which do not have any resistance of their own. So without a resistor, they get very hot, very fast and fail.
The above image shows a schematic. We are using a resistor to limit the current to an LED. The oblong is the resistor. It is the universal symbol in the UK / EU. The triangle with a line and two arrows is the symbol for an LED.