Resistors Test 2/8
electric current
the flow of electrons that flow in a specific conductor or type of metal wire, and pass through a given area
standard values
values between 0-100 Ohms, determined by the tolerance. Does not exceed 100 in ohms value.
Potentiometer
variable resistor with 3 terminals **voltage divider
What impacts the flow of electrons?
Drift velocity and Drift speed
Resistance depends on
1. length factor: shorter/smaller the better 2. diameter (thickness): the more skinny the better 3. temperature: the hotter the wiring (or conductor) the more slower or sluggest the electric current flow will be 4. type of conductor material used: copper, silver, gold, tin foil (aluminum)
Ohm's Law
1.) current found in a metal conductor that is directly proportional to the potential difference across its ends, and inversely proportional to the resistance involved potential difference= current x resistance 2.) Conventional current is always positive 3.) Is not a fundamental law of nature 4.) Explains the use of certain materials 5.) Materials that have a constant resistance over a range of potential differences are associated as ohmic material, non ohmic ex is a diode.
SI unit for current
A (ampere)
Drift speed
many collisions incurred by electrons as they move through a conductor
Drift Velocity
net velocity of a charge carrier moving in an electric field
Carbon resistors
popular; inexpensive + available in standard sizes and wattages **better with time and usage
Wire Wound
resistive wire around a ceramic core **Commercial factory use; high power rating
Metal Film Resistors
superior to carbon resistors **value does not change with age and have improved tolerance
Resistance
a material opposing the flow of electrons, measured in ohms
Two main applications Resistors are used in are...
as storage dividers to limit the flow of current in a circuit
Variable resistors
change their value over a specific range
Resistors
commonly used to perform two functions in a circuit - fall into a fixed
Color Code
determines resistors ohmic value and tolerance
What causes damage to a resistor?
exceeding the power rating
rheostat
has only 2 terminals
Fixed resistors
have only one ohmic value; cannot be adjusted
Resistors are used to..
limit flow of current in a circuit produce a voltage divider