1 electronics conductors and insulators copyright © texas education agency, 2013. all rights...

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Electronics

Conductors and Insulators

Copyright © Texas Education Agency, 2013. All rights reserved.

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Presentation Overview 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


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Terms and DefinitionsA. Resistivity or specific resistance

The electrical resistance of a rod of conducting material having a specified length and cross-sectional area.

B. Conductivity The capacity of a conducting rod of unit length and cross-sectional

area to allow electrical current flow.C. Semiconductor

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 DefinitionsD. Dielectric

A material of very high resistance that is capable of holding or storing an electrical charge.

E. Mil One thousandth (0.001) of an inch

F. Circular mil (cmil) area 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 Insulators (high resistance)

Air or vacuum Bakelite Glass Mica Paper Rubber Shellac

Semiconductors (medium resistance) Germanium Silicon

Conductors (low resistance) Silver Copper Aluminum Gold Tungsten Nickel Iron


What is a Wire?

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


Wire Resistance 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.9Copyright © Texas Education Agency, 2013. All rights reserved.

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Calculating Wire Resistance

Principles 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

Many free electrons 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 American Standard Wire Gauge is

used to check wire sizes. Wire gauge chart

Gauge numbers range from 1 to 40 Wire diameter is measured in

mils (0.001 in.) Cross-sectional area is measured in

1. Circular mils (cmils)2. The diameter in mils squared

The higher the gauge number of a wire 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 ==============================================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. What is the total resistance of 6,000 feet of 24 gauge copper wire at room temperature?

2. What is the total resistance of 155 feet of 8 gauge aluminum wire at room temperature?

3. 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 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 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


1 electronics conductors and insulators copyright © texas education agency, 2013. all rights...

Documents

conducting wire

electrical resistance

wire diameter

crosssectional area

american wire gauge

electrical energy

electrical characteristics

electrical charge