Module 2 : Electrical Conductors and Insulators

Electrical Conductors

Substances with high conductivity, which have very mobile electrons, are called conductors.

Insulators

Substances with low conductivity are called insulators.

Silver

A metal commonly used as an electrical conductor.

Copper

A metal commonly used as an electrical conductor.

Zinc

A metal commonly used as an electrical conductor.

Aluminum

A metal commonly used as an electrical conductor.

Nickel

A metal commonly used as an electrical conductor.

Brass

A metal commonly used as an electrical conductor.

Platinum

A metal commonly used as an electrical conductor.

Iron

A metal commonly used as an electrical conductor.

Tin

A metal commonly used as an electrical conductor.

Lead

A metal commonly used as an electrical conductor.

Class A Insulation

Consists of cotton, silk, paper and materials of paper composition impregnated or immersed in an insulating filler, phenolic resin, or similar resins.

Class B Insulation

Consists of mica, asbestos, or fiberglass; all with a binder.

Class C Insulation

Consists entirely of mica, porcelain, glass, quartz, or similar materials.

Class O Insulation

Consists of cotton, silk, paper, or similar materials that are not impregnated or immersed in an insulating liquid.

Bare Conductor

A conductor having no covering or insulation.

Covered Conductor

Encased within a material of composition and thickness not recognized by code.

Insulated Conductor

Encased within a material of composition and thickness recognized by code.

AWG

American Wire Gauge, preceded by a number which indicates the size of the wire.

MCM

Thousand Circular Mil, M being the Roman numeral for thousand.

Solid Wire

Also known as solid-core or single-strand wire, consists of a one piece of wire on its entire cross section.

Stranded Wire

Wire that consists of multiple strands twisted together, providing more flexibility than solid wire.

Flexibility of Solid Wire

Solid wire has less flexibility than stranded wire.

Historical Note on Wire

The use of wire can be traced as far back as 3,000 B.C., when metal was hammered into sheets, then cut into strips.

Wire Drawing Process

A method characterized by having metal drawn into a series of holes on a drawplate or dies of varying diameters.

Ichabod Crane

An American who introduced the use of a waterwheel as a manufacturing process for wire drawing in 1831.

Stranded Wire

Consists of a group of wires twisted to form metallic.

Insulating Materials

Examples include Rubber, Porcelain, Varnish, Slate, Glass, Mica, Latex, Asbestos, Thermoplastic, Oil, Wax, Dry air, Paper, Silk, and Wood.

Conductors

Materials that allow the flow of electric current, such as Silver, Copper, Aluminum, and Brass.

Insulators

Materials that resist the flow of electric current, such as Rubber, Porcelain, and Slate.

Cables

Electrical conductors larger than wires, typically consisting of two or more wires assembled in a single jacket.

AWG

American Wire Gauge, a U.S. standard set of non-ferrous wire conductor sizes where 'gauge' means the diameter.

Busbar

A rigid electric conductor, usually a metal bar, hollow tube, or rod, which forms a connection between electric circuits.

Properties of Copper

Ductile, malleable, and an excellent conductor of heat and energy; harder than zinc and softer than iron.

Properties of Aluminum

Produced by the formation of many metals, such as feldspar, mica, alum, cryolite, clay, and bauxite.

Resistance Calculation

The resistance of a conductor can be calculated using its resistivity, length, and cross-sectional area.

Circular Mil Area

The total circular mil area is found by multiplying the circular mil area of each strand by the total number of strands.

Number 6 AWG

A size designation for cables, indicating a specific diameter and current-carrying capacity.

Number 10 AWG

A wire size with a diameter of 2.59 mm.

Diameter in CM

The diameter of a wire can be determined in Circular Mils (CM) based on its cross-sectional area.

Cross-sectional Area

The area of a wire's cross-section, which affects its resistance and current-carrying capacity.

Length Reduction

The actual length of a cable may be reduced by 5% of its original length due to twisting of the strands during installation.

Resistance of Copper Conductor

Determined by its resistivity rating and physical dimensions.

Cable Size Designation

Cables are designated by their AWG size, with larger sizes indicating larger diameters.

Electrical Conductors

Wires are electrical conductors which are 8 mm2 (No. 8 AWG) or smaller.

Good Conductors

Materials like Silver and Copper that have high conductivity.

Fair Conductors

Materials like Charcoal and Coke that have moderate conductivity.

Partial Insulators

Materials like Dry Paper and Cotton that have limited insulating properties.

Living Substances

Materials such as Vegetable Substances that can act as insulators.

Moist Earth

Can act as a conductor under certain conditions.

Seawater

A good conductor due to its salt content.

Saline Solutions

Conductive solutions due to dissolved salts.

Graphite

A form of carbon that acts as a conductor.

Lignum Vitae

A dense wood that can act as an insulator.

Ebonite

A hard rubber that is a good insulator.

Circular Mil (CM)

Unit of measuring cross-section size in American Wire Gauge (AWG).

Mil

One-thousandth of an inch (0.001 in.).

Area in CM

Calculated as (diameter in mils)².

Conversion Factor for Square Mil

Square mil = square inch x 0.000001.

Conversion Factor for Square Inch

Square inch = square mil x 1,000,000.

Conversion Factor for Circular Mil

Circular mil = square mils x 1,273.

Millimeter Conversion

Millimeter = inches x 25.4.

Square mm Conversion

Square mm = circular mils x 0.0005067.

Square Mil

The area of a square having its side equal to 1 mil.

Square Mil (SM)

Calculated as 0.7854 x Circular Mils.

Properties of Conductors

Includes characteristics such as size, area, and allowable ampacities.

Allowable Ampacities of Insulated Copper Conductors

Varies based on size and temperature ratings.

Minimum Size of Conductors based on Voltage Rating

Specifies minimum conductor sizes for different voltage ratings.

Moisture-Resistant Thermoplastic

Used in locations that require moisture resistance.

Heat-Resistant Rubber

Rubber that can withstand high temperatures, typically rated at 75°C.

Dry Locations

Areas where moisture is not a concern for electrical installations.

Wet Locations

Areas where moisture may be present and special considerations are needed for electrical installations.

Thermoplastic

A type of plastic that becomes moldable upon heating and solidifies upon cooling.

Varnished Cambric

A type of insulation material used in electrical wiring.

Mineral Insulation (Metal-Sheathed)

Insulation that provides protection against heat and moisture.

Asbestos

A material historically used for insulation but now largely phased out due to health risks.

Cross-Linked Polyethylene

A type of plastic used for insulation that offers enhanced thermal and chemical resistance.

Number of Wires in a Conduit

Determined by the size of the wire and the conduit used.

Insulated Conductor

A conductor that is covered with a non-conductive material to prevent electrical leakage.

Electrical Resistance

The opposition to the flow of electric current, which increases with thinner wires.

Gauge Number

Indicates the diameter of the wire; a higher gauge number means a smaller diameter.

Ampacity

The maximum amount of electric current a conductor or device can carry before sustaining immediate or progressive deterioration.

Diameter in Mils

The measurement of the wire's diameter in mils, where 1 mil = 0.001 inches.