D1 14-20 Flashcards
Malleability
The ability of a material to be rolled or hammered into thin sheets
Ductility
The ability of a material to be drawn into a wire
Ultimate Strength
Mechanical stress a wire can take before breaking
Contact resistance
Resistance between two conductors at a given pressure
What conductor material has the best conductance?
Silver
Copper resistivity per mil-foot equals?
10.4 ohms
Aluminums resistivity per mil-foot is?
17 ohms
Line loss is equal to?
Watts loss (power loss)
Temperature coefficient formula?
Res change= Original res. X coefficient X temp change
And
New res= original res. + res change
Resistance formula
R=K X L Divided by CMA
R= resistance
K=10.4 or 17
CMA=circular mils
What is ambient temperature
Standard normal temp in that specific area.
Why to use copper
Conductance
Oxide resistance
Advantage of stranded wire over solid
Flexibility
Disadvantages of aluminum
Cold flow
Rapid oxidation
Flexible cords have what type of stranding
Bunch
Varnish Cambric for insulator
Motor windings and transformers
White or grey insulation is for
Neutral conductors
Green insulation is for
Bonding
Red/black/or blue wires are assumed to be
Live/hot
What are mineral insulated cables suitable for
Fire-resistant wiring (no flammable materials)
What affects the resistance of a conductor?
Area of it
Type of material
Length
Temperature
What is extra low voltage?
30volts or less
What is low voltage?
31volts to 750volts
What is high voltage?
Over 750v
2 extra low voltage circuits
Doorbell
Thermostat
Loomex or NMSC
Wood structures
300V Max
Hazards with PVC
Can burn/transmit fire
Toxic smoke
Corrode metal when burnt
Voltage drop formula
VD= K x L x amps divided by CMA
1 MCM equal
1CMx 1000
One mil equals
One-thousandth of an inch
A square mill has
More area
Square mil divided by what equals circular mil
.7854
