RESISTORS
SOME USEFUL FACTS ABOUT RESISTORS
1. A resistor is an electronic component whose resistance value tells us about the opposition it offers to the flow of electrical current. Resistance is measured in ohms( ), kilo-ohms ( K ) and is measured in ohms (M ) with 1 M = 1000 K = 1000000. Current (I) flowing through a resistance (R) , voltage (V) across the resistance (R), and the power dissipated as heat (W).
2. More than one resistors are often connected in series or in parallel to get a resistance value that is not available as a standard value (standard resistance values will be discussed a little later). Or to even enhance the wattage rating of what is available. Equivalent resistance (Rs) of more than one resistors connected in series is given by Rs= (R1+R2+R3............) Equivalent resistance ( Rp ) of more than one resistors connected in parallel is given by .
RESISTOR CODING SCHEMES
Resistor Color Code Information
The resistor color code is a long standing standard in both the electronics and electrical industries, indicating the value of resistance of a resistor. Resistance is measured in ohms and there is a foundation for it called Ohm's Law. (Want to know about Ohm's Law? Each color band represents a number and the order of the color band will represent a number value. The first 2 color bands indicate a number. The 3rd color band indicates the multiplier or in other words the number of zeros. The fourth band indicates the tolerance of the resistor+/- 20%, 10% or 5%. In most cases, there are 4 color bands. However, certain precision resistors have 5 bands or have the values written on them, refining the tolerance value even more. There is no standard (TANS) however, for the 5th band. From one manufacturing company to another, the 5th band may indicate 2%, 1%, 1/2% or even closer, according to their own standards. Color bands are usually found on resistors that have a wattage value of 1/8 to 2 watts; though it is rare, there are some 5 watt resistors that are banded.
| Band Color Options | Band #1 Possible | Band #2 Possible | Band #3 Possible | Multiplier Value For Band 3 | Band #4 Value Tolerance |
| Black | | 0 | 1 | 1 | |
| Brown | 1 | 1 | 1 | 10 | |
| Red | 2 | 2 | 2 | 100 | |
| Orange | 3 | 3 | 3 | 1,000 | |
| Yellow | 4 | 4 | 4 | 10,000 | |
| Green | 5 | 5 | 5 | 100,000 | |
| Blue | 6 | 6 | 6 | 1,000,000 | |
| Violet | 7 | 7 | | 10,000,000 | |
| Gray | 8 | 8 | | 100,000,000 | |
| White | 9 | 9 | | 1,000,000,000 | |
| None | 20% | ||||
| Silver | 10% | ||||
| Gold | 5% |
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