NAVEDTRA 14176A, NEETS Mod. 4, Ch. 1 Flashcards
Which unit of measurement is used to determine the cross-sectional area of a square or rectangular conductor?
Square mil
What is the standard unit of measurement of a round wire cross-sectional area?
Circular mil
What can be done to increase the flexibility of wire?
Stranding
What is a heavy copper strap or bar that is used to connect several circuits together?
Bus bar
What is the resistance in ohms offered by a unit volume (the circular-mil-foot or the centimeter cube) of a substance to the flow of electric current?
Specific resistance
What is the reciprocal of conductivity?
Resistivity
What is the most common method of measuring wire size in the Navy?
American Wire Gauge (AWG)
What is a single slender rod or filament of drawn metal called?
Wire
Which type of wire is suitable for carrying an electric current?
Conductor
Which type of conductor is composed of a group of wires or of any combination of groups of wires?
Stranded
Which wire property is used to determine what size is needed for a given load, or current drain?
Current rating
What prepares tables showing the safe current ratings for sizes and types of conductors covered with various types of insulation?
National Board of Fire Underwriters
What is the best conductor?
Silver
What are the two most commonly used conductors?
Copper and Aluminum
Only about what percent of the conductivity of copper does aluminum have?
60
What is the discharge of electricity from the wire when it has a high potential called?
Corona
What are generally referred to as “insulators” or “insulating material.”?
Nonconductors
Insulation resistance along with what else are the two fundamental properties of insulating materials?
Dielectric strength
What is the resistance to current leakage through the insulation materials called?
Insulation resistance
What can insulation resistance be measured with that wont damage the insulation?
Megger
What is the ability of an insulator to withstand potential difference?
Dielectric strength
What is normally used for low- or medium-range voltage?
Rubber insulation
Which standard has the National Electrical Code (NEC) adopted as the minimum requirements for rubber insulation as specified by Underwriters’ Laboratories?
Code-graded rubber
Latex rubber is a high-grade compound consisting of what percent of unmilled grainless rubber?
90
Which rubber compound does not carry the “R” designator for many of its applications?
Silicone
What is one of the most common types of plastic insulating materials?
Thermoplastic
What is cotton cloth that has been coated with an insulating varnish known as?
Varnished cambric
Varnished cambric and paper insulation for cables are the two types of insulating materials most widely used at voltages above how many volts?
15,000
What is a high-temperature insulation used extensively in aircraft and equipment installations?
Extruded polytetrafluoroethylene
How many degrees Celsius is Fluorinated Ethylene Propylene (FEP) rated at?
200
Which type of fibers have been found to cause severe lung damage and cancer of the gastrointestinal tract?
Asbestos
How many different types of asbestos wire does the NEC have designators for?
Eight
What serves as a satisfactory insulation for extremely high-voltage cables when it is impregnated with a high grade of mineral oil?
Paper
What type of wire is used on the coils of meters, relays, small transformers, motor windings, and so forth?
Magnet wire
What is the thinnest insulating coating that can be applied to wires?
Enamel
Which type of cable was developed to meet the needs of a noncombustible, high heat-resistant, and water- resistant cable?
Mineral-insulated (MI)
Up to how many electrical conductors does MI cable have?
Seven
What are the two categories of materials that make up the protection for a wire or cable?
Nonmetallic or metallic
What is by far the most common type of nonmetallic material used to protect wires and cables?
Fibrous braid
Which material is commonly used only in special classes of service and is made as a solid felted covering for a cable?
Unspun felted cotton
What are the two types of metallic wire protection?
Sheath or armor
Lead-sheathed cable is one of three types currently being used: alloy lead, pure lead, and what else?
Reinforced lead
What is defined as two concentric wires, cylindrical in shape, separated by a dielectric of some type?
Coaxial cable