Resistor  Passive component with a known resistance.
The value of resistance is usually shown by a set of coloured bands on the body of the component.  The resistor shown above is coded Orange, Green, Blue with a silver tolerance band. Using the following table the resistance may be calculated from the first three bands, Orange = 3, Green = 5 and the multiplier is Blue = 106 = 1000000. The silver band indicates a tolerance of ±10% Therefore, the resistance is 35x106±10% Ohms
| Colour | Band 1 | Band 2 | Band 3 | | Black | 0 | 0 | 100 = 1 | | Brown | 1 | 0 | 101 = 10 | | Red | 2 | 0 | 102 = 100 | | Orange | 3 | 0 | 103 = 1000 | | Yellow | 4 | 0 | 104 = 10000 | | Green | 5 | 0 | 105 = 100000 | | Blue | 6 | 0 | 106 = 1000000 | | Violet | 7 | 0 | 107 = 10000000 | | Grey | 8 | 0 | 108 = 100000000 | | White | 9 | 0 | (none) | | - Tolerance Codes
- Gold = ±5%
- Silver = ±10%
- None = ±20%
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There are a number of different types of resistors designed for different applications.
- Carbon Film
- A carbon film deposited on a small ceramic cylinder.
- Metal Film
- A thin film or metal particle mixture is used to control the resistance.
- Wire Wound
- A length of resistance wire wound onto a tube. These are very accurate and able to carry large currents.
The power disipated by a resistor is given by Joule′s law:  - where
- W = power disipated [Watt]
- I = current [Ampere]
- R = resistance [Ohm]
- V = potential difference across resistor [Volt]
| Enter two values and the other values will be calculated. -
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See also: Light Dependent Resistor, Resistance, Thermistor.
  
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