Electronics
Conductors and Insulators
Copyright © Texas Education Agency, 2013. All rights reserved.
1
Presentation Overview
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Terms and Definitions
Conducting and Insulating Materials
Functional Features of Electrical Conductors
Functional Features of Electrical Insulators
Applications of Conductors
Types of Wire Conductors
Wire Sizes and Gauge Numbers
Properties of Conducting Materials
Wire Resistance
Desirable Properties of Wire Insulation
Copyright © Texas Education Agency, 2013. All rights reserved.
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Terms and Definitions
Resistivity or specific resistance
A.
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The electrical resistance of a rod of conducting material having a
specified length and cross-sectional area.
Conductivity
B.
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The capacity of a conducting rod of unit length and cross-sectional
area to allow electrical current flow.
Semiconductor
C.
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A material having relatively high resistance at room temperature
whose electrical characteristics can be changed and controlled by
various techniques (such as by adding other elements
called “impurities”).
Examples include germanium and silicon, which function as
transistors, chips, and diodes after the impurities arsenic or gallium
are added to them.
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Terms and Definitions
Dielectric
D.
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A material of very high resistance that is capable of holding or
storing an electrical charge.
Mil
E.
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One thousandth (0.001) of an inch
Circular mil (cmil) area
F.
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The cross-sectional area of a wire calculated by squaring the wire
diameter in mils.
For example, the cmil area of a conductor having a diameter of 7.0
mils is 49.0 cmils (7.0 squared).
(Note: This method of calculating cross-sectional area is used only for
conducting wires, and is done as a convenience to avoid having to calculate
cross-sectional area by means of the metric system and formula.)
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Conducting and Insulating
Materials
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Insulators (high resistance)
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Semiconductors (medium resistance)
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Air or vacuum
Bakelite
Glass
Mica
Paper
Rubber
Shellac
Germanium
Silicon
Conductors (low resistance)
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Silver
Copper
Aluminum
Gold
Tungsten
Nickel
Iron
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What is a Wire?
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A wire is the most common example of an
electrical conductor.
Wires are used in circuits to deliver voltage and
current to where it is needed.
Circuit components convert electrical energy into
some other useful form of energy.
Wires come in many different shapes and sizes.
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Applications of Conductors
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Types of Wire Conductors
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Wire Resistance
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Specific resistance is a function of the area of a conductor
measured in units of circular mils.
The American Wire Gauge (AWG) gives the size of the
conducting wire as a whole number.
 The larger the gauge number, the skinnier the wire.
 The smaller the gauge number, the thicker (fatter)
the wire.
 There is a relationship between area in circular mils and
the AWG, but it is complex.
Wire resistance is a function of length.
 As length increases, wire resistance increases.
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Calculating Wire Resistance
Principles
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The thicker the wire, the less its resistance.
The longer the wire, the higher its resistance.
Formula for wire resistance where
 R = total resistance
 ρ = specific resistance
 L = length of the wire
 A = cross-sectional area in
circular mils
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Functional Features of Electrical
Conductors
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Many free electrons
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For good conduction of
electricity
Low resistance to
electrical current
Little voltage (IR) drop
Low power dissipation
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Wire Sizes and Gauge Numbers
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American Standard Wire Gauge is
used to check wire sizes.
Wire gauge chart
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Gauge numbers range from 1 to 40
Wire diameter is measured in
mils (0.001 in.)
Cross-sectional area is measured in
1.
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Circular mils (cmils)
The diameter in mils squared
The higher the gauge number
of a wire
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The smaller its wire diameter
The smaller its cross-sectional area
The higher its resistance
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WIRE TABLE FOR SOLID, ROUND COPPER CONDUCTORS
Size
Diameter
Cross-sectional area
Weight
AWG
inches
cir. mils
sq. inches lb/1000 ft
=============================================
4/0 -------- 0.4600 ------- 211,600 ------ 0.1662 ------ 640.5
3/0 -------- 0.4096 ------- 167,800 ------ 0.1318 ------ 507.9
2/0 -------- 0.3648 ------- 133,100 ------ 0.1045 ------ 402.8
1/0 -------- 0.3249 ------- 105,500 ----- 0.08289 ------ 319.5
1 -------- 0.2893 ------- 83,690 ------ 0.06573 ------ 253.5
2 -------- 0.2576 ------- 66,370 ------ 0.05213 ------ 200.9
3 -------- 0.2294 ------- 52,630 ------ 0.04134 ------ 159.3
4 -------- 0.2043 ------- 41,740 ------ 0.03278 ------ 126.4
5 -------- 0.1819 ------- 33,100 ------ 0.02600 ------ 100.2
6 -------- 0.1620 ------- 26,250 ------ 0.02062 ------ 79.46
7 -------- 0.1443 ------- 20,820 ------ 0.01635 ------ 63.02
8 -------- 0.1285 ------- 16,510 ------ 0.01297 ------ 49.97
9 -------- 0.1144 ------- 13,090 ------ 0.01028 ------ 39.63
10 ------- 0.1019 ------- 10,380 ------ 0.008155 ----- 31.43
11 -------- 0.09074 ------- 8,234 ------ 0.006467 ----- 24.92
12 -------- 0.08081 ------- 6,530 ------ 0.005129 ----- 19.77
13 -------- 0.07196 ------- 5,178 ------ 0.004067 ----- 15.68
14 -------- 0.06408 ------- 4,107 ------ 0.003225 ----- 12.43
15 -------- 0.05707 ------- 3,257 ------ 0.002558 ----- 9.858
16 -------- 0.05082 ------- 2,583 ------ 0.002028 ----- 7.818
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WIRE TABLE FOR SOLID, ROUND COPPER CONDUCTORS
Size
Diameter
Cross-sectional area
Weight
AWG inches
cir. mils
sq. inches lb/1000 ft
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17 -------- 0.04526 ------- 2,048 ------ 0.001609 ----- 6.200
18 -------- 0.04030 ------- 1,624 ------ 0.001276 ----- 4.917
19 -------- 0.03589 ------- 1,288 ------ 0.001012 ----- 3.899
20 -------- 0.03196 ------- 1,022 ----- 0.0008023 ----- 3.092
21 -------- 0.02846 ------- 810.1 ----- 0.0006363 ----- 2.452
22 -------- 0.02535 ------- 642.5 ----- 0.0005046 ----- 1.945
23 -------- 0.02257 ------- 509.5 ----- 0.0004001 ----- 1.542
24 -------- 0.02010 ------- 404.0 ----- 0.0003173 ----- 1.233
25 -------- 0.01790 ------- 320.4 ----- 0.0002517 ----- 0.9699
26 -------- 0.01594 ------- 254.1 ----- 0.0001996 ----- 0.7692
27 -------- 0.01420 ------- 201.5 ----- 0.0001583 ----- 0.6100
28 -------- 0.01264 ------- 159.8 ----- 0.0001255 ----- 0.4837
29 -------- 0.01126 ------- 126.7 ----- 0.00009954 ---- 0.3836
30 -------- 0.01003 ------- 100.5 ----- 0.00007894 ---- 0.3042
31 ------- 0.008928 ------- 79.70 ----- 0.00006260 ---- 0.2413
32 ------- 0.007950 ------- 63.21 ----- 0.00004964 ---- 0.1913
33 ------- 0.007080 ------- 50.13 ----- 0.00003937 ---- 0.1517
34 ------- 0.006305 ------- 39.75 ----- 0.00003122 ---- 0.1203
35 ------- 0.005615 ------- 31.52 ----- 0.00002476 — 0.09542
36 ------- 0.005000 ------- 25.00 ----- 0.00001963 — 0.07567
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Properties of Conducting Materials
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Example Problems
1.
2.
3.
What is the total resistance of 6,000 feet of 24
gauge copper wire at room temperature?
What is the total resistance of 155 feet of 8
gauge aluminum wire at room temperature?
What is the specific resistance of platinum if
200 feet of 12 gauge platinum wire is 1.93 Ω at
room temperature?
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Functional Features of Electrical
Insulators
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Few free electrons
(poor conduction of
electricity)
High resistance to
electrical current
Hold and store an
electrical charge
High dielectric strength
(high voltage
breakdown point)
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Desirable Properties of Wire
Insulation
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High resistance
Toughness
Flexibility
Non-brittleness with aging
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Presentation Summary










Terms and Definitions
Conducting and Insulating Materials
Functional Features of Electrical Conductors
Functional Features of Electrical Insulators
Applications of Conductors
Types of Wire Conductors
Wire Sizes and Gauge Numbers
Properties of Conducting Materials
Wire Resistance
Desirable Properties of Wire Insulation
Copyright © Texas Education Agency, 2013. All rights reserved.
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