Resistors
De BISAWiki
A resistor can be an electronics component that opposes the flow of electrons in a electrical circuit. There are several varieties of resistors available, as well as in a variety of resistance ratings, but generally each resistor will fall into one of two categories: fixed resistors and variable resistors. As the names indicate, fixed resistors have a fixed and unchangeable resistance value, while variable resistors have variable resistance values. What follows can be a brief discussion of the various common kinds of fixed and variable resistors within the electronics world.
panasonic capacitors Fixed Resistors
Fixed resistors are discrete electronics components available in a number of resistance values and rated in Ohms. Common forms of fixed resistors include carbon composition resistors, carbon film resistors, metal film resistors, wire wound resistors, and foil resistors. Each in the above kinds of fixed resistors has particular characteristics for that resistor type for particular purposes. For example, wire wound resistors generally are able to handle larger amounts of power than, say, carbon composition resistors, however their wire coils often bring about unwanted inductive reactance in AC or RF circuits. Fixed resistors are often marked according to the conventional resistor color code.
Variable Resistors Variable resistors, because name implies, are resistors whose resistance will be able to be varied, whether manually or automatically. Common kinds of variable resistors include rheostats and potentiometers and will often be differentiated derived from one of another by way of the linearity of the variable resistance. For example, potentiometers can be found in linear-taper varieties and logarithmic-taper varieties that differ in the linearity of the variability because the potentiometer is turned. Potentiometers in many cases are low-Wattage devices, while rheostats are often used for high-power applications in industrial electronics.
The choice from the fixed and variable resistor in circuit-design will be based on upon whether one's circuit requires resistance values or circuit characteristics that require variability or stability. For example, you are constructing a radio receiver that'll be fixed on a single radio frequency, then this circuit that is certainly composed entirely of fixed-value resistors and also other components will most likely suffice. If however, the first is building a motor control circuit that demands variation in motor speed, an adjustable resistor would be a more appropriate choice since a variable resistor might be used to vary the speed of the motor. Thus there can be a need for both fixed and variable resistors in electronics circuits, plus a familiarity with both kinds of resistors is essential if one is to have comprehensive knowledge of the numerous types of circuits that may call for resistors.
