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What are the two functions of a resistor
Limit flow of current, and produce a voltage divider
What is a short circuit
an electric circuit that contains no resistance to limit the flow of current.
What is a voltage divider
a circuit that generally is constructed by connecting resistors in series to produce desired voltage drops across the resistors.
What is a fixed resistor
they have only one ohmic value, which cannot be changed or adjusted.
What are the three fixed resistors
composition carbon, metal film, and wire-wound resistors.
Composition carbon resistor
resistors that are made by mixing carbon with other compounds to produce a substance that has a known resistance.
Why are composition carbon resistors popular/advantage
very popular for most applications because they are inexpensive and readily available.
How can you tell the power rating of a resistor
The power rating of the resistor is indicated by its size.
Disadvantage of composition carbon resistor
Carbon resistors will change their value with age or if they are overheated. Carbon resistors generally increase instead of decrease in value.
Metal film resistor
resistors that are produced by coating a nonconductive material with a film of metal.
How are metal film resistors constructed
Metal film resistors are constructed by applying a film of metal to a ceramic rod in a vacuum
How are metal film resistors superior to carbon resistors
Metal film resistors do not change their value with age, and their tolerance is generally better than that of carbon resistors.
Tolerance for metal film resistors is generally what
Metal film resistors generally range in tolerance from 2% to 0.1%.
Metal film resistor disadvantage
The disadvantage of the metal film resistor is that it costs more.
Carbon film resistor
This resistor is made by coating a ceramic rod with a film of carbon instead of metal.
Advantages of carbon film resistor
Carbon film resistors are less expensive to manufacture than metal film resistors and can have a higher tolerance rating than composition carbon resistors.
Metal Glaze Resistor
This resistor is made by combining metal with glass.
What are the typical tolerance ratings for metal glaze resistors
Tolerance ratings of 2% and 1% are common.
Wire-wound resistors
resistors that are constructed by winding resistive wire around a nonconductive material.
The resistance of a wire-wound resistor is determined by three factors:
The type of material used to make the resistive wire
The diameter of the wire
The length of the wire
How should wire wound resistor
should be mounted vertically and not horizontally.
Advantages of wire wound resistors
Wire-wound resistors can operate at higher temperatures than any other type of resistor.
Diadvatges of wire wound resistors
The disadvantage of wire-wound resistors is that they are expensive and generally require a large amount of space for mounting.
Variable Resistors
A variable resistor is a resistor whose values can be changed or varied over a range. Variable resistors can be obtained in different case styles and power ratings.
Multiturn variable resistors
operate by moving the wiper arm with a screw of some number of turns. They generally range from 3 turns to 10 turns.
