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Electrical
- Introduction
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If you experience any problems with the site, please contact Pete Hoffman immediately so corrections can be made. Pete can be reached on campus, via email at phoffman@swtc.edu or by phone at 1.800.362.3322 ext 2727.
Resistor Color Codes
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.