Resistor are a very common electric component. Practically all circuits require resistors to work. There are many possible uses for resistors like current limiter or feedback component. Due to the number of possible usage, I cannot name all of them. A typical resistor looks like this one.
If you look closely, you will see four strips of colors on the resistor. These colors denote the value of the resistors. Here are the possible colors and their corresponding values.
| Color | Value | Multiplier | Tolerance |
|---|---|---|---|
| Black | 0 | 1 | |
| Brown | 1 | 10 | |
| Red | 2 | 102 | |
| Orange | 3 | 103 | |
| Yellow | 4 | 104 | |
| Green | 5 | 105 | |
| Blue | 6 | 106 | |
| Violet | 7 | 107 | |
| Gray | 8 | 108 | |
| White | 9 | 109 | |
| Gold | 0.1 | 5% | |
| Silver | 0.01 | 10% |
The resistor values are read by using the first two values as the digits and then multiplied by the third multiplier. The fourth color serves as the tolerance of the resistor. The tolerance of the resistor represents the maximum and minimum possible deviation of the actual resistance with that of its coded resistance. In the figure the colors are as follows: green, blue, yellow, and gold. This comes out to be 560 k ohms with 5% tolerance. To get this we first get the equivalent of the first two colors, green (5) and blue (6), 56 and then multiply this by the multiplier of the third color, yellow, 104. 56 * 104 = 560 k ohms. The fourth color is gold which represents tolerance means that the tolerance is 5%. The maximum and minimum resistance is represented by color resistance plus or minus 5% of the color resistance.
The schematic symbol for a resistor looks like this.
The two common combinations for resistors and their equivalent resistances.
| SERIES RESISTORS |  |
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| PARALLEL RESISTORS |  |
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The formulas writtern apply for combinations of two resistors but can easily be extended to an unlimited number of resistors. The thing is, as long as the resistors are connected in series, the equivalent or total resistance is just the sum of all the resistances. For parallel resistors, the sum of the reciprocals of the individual resistances is the reciprocal of the equivalent or total resistance.
If you try to solve these equations, you will see that resistors in series always increase in resistance while resistors in parallel always decrease in their equivalent resistance. You can use these properties to get a resistance even with the lack of available resistors.
