Chapter two :o Flashcards
(17 cards)
what are four things that affect Resistance?
Type of material
Length
Cross sectional area
Temperature
the amount of change of resistance per unit change in temperature is known wut?
The Temperature Coefficient
What is resistance represented by?
R,
is measured in OHMs
the omega symbol
what are the three basic types of resistors?
Fixed, tapped and variable
what are four types of fixed resistors :3?
Carbon Composition, wire-wound, film and surface mount.
Carbon composition
The oldest and most common type of resistor. expensive and not really used as much anymore :c
printed carbon resistor
can be printed directly onto the PCB :3
wire wound fixed resistor
used to control large amounts of current. they are constructed by winding resistance wire on a porcelain base. very accurate
film fixed resistors
are made by evenly depositing a film of resistive material onto a high grade ceramic tube or rod
surface mount resistors
developed in response to the demand for smaller electronic comnents, have no leads.
Tapped resistors
have taps that allow different resistive values to be selected.
variable resistor
two most common: rheostat and potentiometer. both allow resistive values to be changed while equipment is in operation.
two types of rheostat
metallic for average currents
carbon for very small currents.
potentiometer
is used to control or vary the amount of voltage used in circuits
resistance varies inversely with
size of the conductor’s Cross section. thicker wire, lower resistance
resistance varies directly with
the longer the wire or conductor, the more resistance it has
if temperature causes resistance of a material to decrease it is called:
Negative Temperature Coefficient
