Why Do Electrical Resistors Have Colored Bands Across Them?
The multi-colored bands on an electrical resistor serve to identify the operational characteristics of the resistor with a special numbering system. These characteristics, and their values, are important to ensure the use of the proper resistors, in the proper way, in circuits.
Other People Are Reading
-
Resistence
-
The first three bands on a resistor represent the value of the resistor in ohms, which is the measurement unit of resistance. The first two bands represent raw numerals from one to ten and the third represents a multiplier ranging from x0 to x1,000,000,000. On some newer resistors the third band can also represent a divider of either /10 or /100.
Tolerance
-
The fourth band represents how much the resistor may vary, plus or minus, from the first three bands because of manufacturing variations. This factor is called "tolerance." The value represented by this band can be from plus or minus .05 percent to 20 percent.
-
Additional Bands
-
If a resistor has five bands, and the fourth band is gold or silver (colors used only to indicate tolerance), the fifth band represents the temperature coefficient: how many parts-per-million (ppm) the resistor may vary because of temperature variations. If the fourth band is any other color, it changes the way the bands calculate to give a more refined resistance value. The first three bands will represent raw numbers, the fourth is the multiplier and the fifth is the tolerance. Occasionally, these resistors will have a sixth band that represents its temperature coefficient.
-
References
Resources
- Photo Credit widerstand, resistor image by Sascha Zlatkov from Fotolia.com
