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Resistors are identified by a standard color coding system. Therefore, it is necessary to be familiar with this system. The colors are read from left to right.
Color 

Significant Digits 
Multiplier 
Tolerance 
Black 

0 


Brown 

1 
0 

Red 

2 
00 
2% 
Orange 

3 
000 

Yellow 

4 
0,000 

Green 

5 
00,000 

Blue 

6 
000,000 

Violet 

7 


Grey 

8 


White 

9 


Gold 


multiply by 0.1 
5% 
Silver 


multiply by 0.01 
10% 
No Value 



20% 
This first two bands translate directly into numbers (example: red = 2, red = 2, etc). The third band is called a Multiplier, this means the number of zeros you add after the first two digits to get the Ohm value (example: brown = 0). So one zero is added after the first two numbers. Therefore 220 ohms is the resistance value of the resistor. The fourth band is called the Tolerance signifier This indicates how much the actual value might vary from the specified value shown by the color bands. If the resistor measures more than the allowed specified value, it is not useable. The more expensive resistors are higher quality, so the specification is tighter. 
Some circuits require precision resistors to operate correctly, so never use a replacement resistor with a wider tolerance. Also, resistors must have the proper wattage value (this indicates the amount of heat a resistor can handle). Since resistors restrict the flow of electricity, friction causes heat to build up heat inside the component. The resistor needs to be large enough to dissipate the heat into the surrounding area without changing its own value beyong the tolarance allowed.