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Resistors are components, which resist or limit the flow of electric current in a circuit. They are designed to protect a circuit. The unit of measure is the ohm.
An additional important characteristic is the wattage rating which indicates the power needed for the resistor to function.
Resistors are rated with a tolerance, which indicates the upper and lower limits of variation from a components nominal value i.e., an allowable deviation. These ratings are usually indicated by a % value. The lower the % ratings are on a part the better the tolerance.
Most film resistors are identified by a system of different color bands indicating the ohms, tolerance and a failure rate when applicable.
The wattage rating is determined by size. Here is a chart of the size for most film resistors.
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