Resistors

Carbon film resistors

a resistor that is made by coating nonconductive material with a film of carbon

Composition carbon resistor

resistors made by mixing carbon with other compounds to make a substrate with a known resistance

Fixed Resistor

resistor that has a value that cannot be changed

Metal Film Resistor

resistor made by coating a nonconductive material with a metal film

Metal Glase Resistor

resistor made by applying a mix of metal and glass to a nonconductive material

Multiturn variable resistor

variable resistor that requires multiple turns to change their resistance values

When is a multiturn variable resistor used

when precise control of measurement is needed

Potentiometer

variable resistor that has a sliding contact that is used as a voltage divider

Tolerance

amount of variation from a standard value that is permissible

Variable resistor

resistor whose resistance value can be varied between its minimum and its maximum values

Voltage divider

circuit that generally is constructed by connecting resistors in series to produce desired voltage drops across the resistors

Wire wound resistors

resistors that are constructed by winding resistive wire around a nonconductive material

Two purposes of resistors

limit current flow

voltage dividers

How is resistance related to area

they are inversely proportional (if area increases, resistance decreases)

How is resistance related to length

they are directly related (if length increases resistance increases)

List the types of fixed resistors

composition carbon \n metal film \n metal glaze \n carbon film \n wire wound

Disadvantage(s) of carbon composition resistors

they change value as they age or if they are overheated

Advantage(s) of metal film resistors over carbon composition

their value doesn’t change with age \n have better tolerance

What determines the resistance of a wire wound resistor

type of material used to make the wire \n diameter of the wire \n length of the wire

Why are carbon resistors widely used

they are inexpensive

How are metal glaze resistors made

combining metal with glass

When are wire wound resistors used

when a higher power rating is needed

Major advantage of wire wound resistors

they can operate at a higher temperature than other resistors

How should hollow wire wound resistors be mounted

vertically to allow air flow

What happens if the power rating of a resistor is exceeded

the resistor can be damaged

What unit is used to describe power ratings of resistors

Watts

What does the power rating of a resistor describe

the amount of heat that must be dissipated by the resistor