Resistors
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[edit] Resistors
Resistors are among the most simple electronic components, and are found in nearly every electronic assembly. Their job is to control current. The current which will flow through a resistor is directly proportional to the voltage across it. The basic equation around which all this revolves is V=IR
Where:
V = voltage, measured in Volts (V)
I = current, measured in Amperes (or simply Amps)(A)
R = resistance, measured in Ohms.(Ω)
What this means is that a 10 Ohm resistor with 12 Volts across it will have 1.2 Amps passing through it.
[edit] Identifying resistor values
Since they are usually very small devices, it's impractical to try to print the value on the body of the component. Instead they use coloured bands to indicate the value.
Common resistors have three bands to indicate the value, and a fourth for the tolerance. The colours correspond to numbers as outlined in the following table:
| Colour | band 1 | band 2 | band 3 | band4 |
|---|---|---|---|---|
| Black | 0 | 0 | ×100 | |
| Brown | 1 | 1 | ×101 | ±1% |
| Red | 2 | 2 | ×102 | ±2% |
| Orange | 3 | 3 | ×103 | |
| Yellow | 4 | 4 | ×104 | |
| Green | 5 | 5 | ×105 | |
| Blue | 6 | 6 | ×106 | |
| Violet | 7 | 7 | ×107 | |
| Gray | 8 | 8 | ×108 | |
| White | 9 | 9 | ×109 | |
| Gold | ×0.1 | ±5% | ||
| Silver | ×0.01 | ±10% |
The multiplier can be considered equivalent to the number of zeroes after the first two digits. So, a 120Ω resistor will have the combination Brown, Red, Brown. Similarly, a 12,000Ω will be Brown, Red, Orange.
The tolerance band is spaced further away from the rest of the bands, to avoid confusion caused by reading from the wrong end.