Conductors Flashcards
How many ways does the electrical industry in North America commonly use to label the size of conductors?
two
AWG - American Wire Gauge
cmil - Circular mil
For the same length of conductor, moving from one AWG size to a conductor three AWG sizes smaller, (for example, from a #3 AWG to #6 AWG) the resistance of the smaller size would be approximately:
twice as great
What is the temperature coefficient of copper and aluminum?
0.0039
List four factors that affect resistance in a conductor:
M-Material
A-Area (Cross section)
L-Length
T-Temperature
Define resistivity
The resistance for a specific volume of material
What is the SI measurement unit for resistivity?
Ohm-metre (Ω.m)
What is the resistivity of copper @ 20°C
Resistivity of copper is 1.72x10-8Ω.m
What is the resistivity of aluminum @ 20°C
Resistivity of aluminum is2.83x10-8Ω.m
What is the Resistance formula that is used to determine Voltage or Line Drop?
R = ρ × (l / A)
What is the formula for the resistance change with temperature?
Rnew = Rold (1 + α (Tnew - Told)) ; Where α is the temperature coefficient specific for each material
To determine the resistance of a conductor that is one #AWG size bigger, what short cut can you apply?
Multiply the resistance value by 1.26
The number of electrons that an atom of a good conductive material would have in its outer shell would be
1,2 or 3
What is a mil?
A mil is one thousands of an inch (1/1000)
How do you calculate the cross-sectional area of a conductor in circular mils (cmils)
The square of the diameter in mils. Usually mils (thousands of mils) (page 21)
What is the percentage change in area for each gauge size change in the AWG wire table?
26%
