104b conductors Flashcards
Classification of material conductors
Good and poor conductors depending on amount of electrons per cubic centimetre.
It is how much voltage a material can withstand before breaking down
Dielectric strength
Semiconductors
Neither good conductors nor good insulators
The amount of voltage and polarity of the applied voltage can make the material either conduct or not conduct
Silicon and germanium are the most common materials
Conductors
Current is high
Resistance is low
Outer electrons are easily freed
Has many free electrons
Silver is the best but copper and aluminum are cheaper
Insulator
Electron flow (current) is low
Resistance is high
Outer electrons are tightly bound to atom NOT easily free
Has fewer free electrons
Glass, rubber, plastic, oil and air
Chosen depending on: ambient temperature, voltage, physical protection
What is Dielectric strenght
Is the electrical insulating strength of a material measured in kilovolts per milimetre kV/mm
What is called a conductor
A conductive material that is formed into wires, cables or busbars
Properties of Copper conductors
Low R
Durable
Pliable
Easy to work with
Properties of Aluminum conductors
Cheaper
Lighter
Typically used in larger sizes
Properties of Steel conductors
High tensile strength
Used in special cables, EMT and boxes
What are the forms of conductors
Solid (rectangular and circular) and Stranded
What are the 4 factors that affect the resistance
Material
Area (cross-sectional)
Length
Temperature
What is resistivity
One cubic meter of the material at 20C
Measured in ohms-metres
What is temperature coefficient
Amount of resistance change for each change in Celsius
Ce code R 4-002 minimum size insulated conductor
14 AWG copper
What is Section 4 of CE Code about
Ampacity insulation, installation methods, conductor protection and correction factors
CE Code R 4-004 apply correction factors T5C T5A depending on
T5C four or more conductors exclusive of neutral and bonding conductors, T5A ambient temperature exceeding 30C
Maximum allowable ampacity on NSC is specified in Tables
T36A and T36B
R 4-004 ampacity of conductors of different temperature ratings in the same raceway is determined:
Conductor having the lowest temperature rating
R 4-006 Maximum conductor termination temperature not marked
60C for equipment rated not more than 100A
R 4-010 Minimum size of flexible cords
18 AWG copper
27 AWG tinsel cord
R 4-018 Minimum size of a service neutral
10 AWG copper
R 4-032 identification of 1-phase 3 wire
1 black 1 red 1 white
