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