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BASIC NEC 2023

Wire & Cable Fundamentals Practice Test

Free online wire and cable fundamentals practice test. 25 basic electrical questions on solid vs stranded conductors, copper vs aluminum, wire gauge, and conductor color coding. Good for electrician exam prep.

TOPICS COVERED

Conductor Types Conductor Materials Wire Gauge Insulation Types Conductor Color Coding Conductor Resistance

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Every electrical circuit depends on the wire (conductor) carrying the current. Understanding the difference between solid and stranded conductors, copper vs. aluminum, how the American Wire Gauge (AWG) system works, and the general meaning behind common conductor color conventions gives you the foundation for everything else in wiring work — before you ever open an NEC ampacity table.

25

Questions

38 min

Time

75%

Pass

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Wire & Cable Fundamentals Practice Test — Question List

Question 1: Compared to a solid conductor of the same gauge, a stranded conductor is generally:

More flexible
Less flexible
Exactly as rigid
Unable to carry any current

Question 2: Solid conductors are commonly used for which type of application?

Fixed, in-wall branch circuit wiring that does not need to flex
Portable extension cords that get coiled and moved constantly
Vibrating machinery connections needing constant flexing
Robotic arm wiring that moves continuously

Question 3: Stranded conductors are commonly used for which type of application?

Cords, portable equipment, and locations where the conductor must flex repeatedly
Only for underground direct-buried service laterals
Only inside sealed conduit that never moves
Never used in real installations

Question 4: Compared to aluminum, copper is generally:

A better conductor (lower resistance) for the same cross-sectional area
A worse conductor than aluminum
Exactly identical in conductivity to aluminum
An insulator, not a conductor

Question 5: Why must an aluminum conductor generally be a larger size than a copper conductor to carry the same amount of current?

Aluminum has higher resistance than copper for the same size, so a larger cross-section is needed to keep resistance (and heating) low enough
Aluminum is a poor conductor with no practical use in wiring
Aluminum conductors are always used at a lower voltage
There is no real reason, it is just tradition

Question 6: In the American Wire Gauge (AWG) system, which statement is correct?

A bigger AWG number means a smaller wire
A bigger AWG number means a bigger wire
AWG numbers have nothing to do with wire size
All AWG sizes are physically identical

Question 7: Which of these two conductors is physically LARGER: 12 AWG or 6 AWG?

12 AWG
6 AWG
They are the same size
Cannot be determined from AWG alone

Question 8: The letters in a wire insulation type code like "THHN" generally describe:

Insulation properties such as heat resistance and whether it is suitable for wet or dry locations
The exact AWG size of the conductor
The manufacturer's brand name only
The color of the conductor

Question 9: An insulation designation that includes a "W" (such as XHHW) generally indicates the conductor is rated for use in:

Wet locations
Underwater use only, never above ground
Only extremely cold locations
Only aluminum conductors

Question 10: UF (underground feeder) cable is generally designed for:

Direct burial in the ground without additional conduit protection in many cases
Indoor decorative lighting displays only
High-voltage transmission lines only
Only aboveground overhead spans

Question 11: NM (nonmetallic-sheathed) cable, often called by a common brand name, is most commonly used for:

General-purpose indoor residential branch circuit wiring
Direct underwater submersion only
High-temperature furnace wiring only
Exclusively for three-phase industrial motors

Question 12: By general US wiring convention, black, red, and blue conductor insulation colors are most commonly used to identify:

Ungrounded ("hot") conductors
The grounded neutral conductor
The equipment grounding conductor only
Communication cable only

Question 13: By general US wiring convention, white conductor insulation is used to identify:

The grounded (neutral) conductor
An ungrounded hot conductor
The equipment grounding conductor
A high-voltage-only conductor

Question 14: By general US wiring convention, green (or bare copper) conductor insulation identifies:

The equipment grounding conductor
An ungrounded hot conductor
The neutral conductor
A communications-only conductor

Question 15: As a conductor gets LONGER (with the same cross-sectional area), what happens to its total resistance?

It increases
It decreases
It stays exactly the same
It becomes zero

Question 16: As a conductor gets THICKER (larger cross-sectional area, same length), what happens to its total resistance?

It decreases
It increases
It stays exactly the same
It becomes infinite

Question 17: "Skin effect" in an AC conductor refers to the tendency of current to:

Concentrate near the outer surface of the conductor rather than flow evenly through its whole cross-section
Flow only through the very center of the conductor
Stop flowing entirely at high frequency
Have no relationship to frequency at all

Question 18: A "circular mil" is a unit used to describe:

The cross-sectional area of a round conductor
The voltage rating of a conductor
The length of a conductor in a bundle
The temperature rating of the insulation

Question 19: A stranded conductor and a solid conductor of the same AWG size have approximately:

The same current-carrying capacity, since they have roughly the same total cross-sectional area
No relationship to each other at all
Stranded is always rated for twice the current of solid
Solid is always rated for twice the current of stranded

Question 20: Between copper and aluminum, which is the more commonly used conductor material in typical residential branch-circuit wiring today?

Copper
Aluminum
Steel
Glass fiber

Question 21: For a very long conductor run, electricians often choose a LARGER wire size than the bare minimum ampacity requires, mainly to help control:

Voltage drop
The wire's color
The insulation's smell
The manufacturer's warranty length

Question 22: Between two stranded conductors of the same overall AWG size, the one made of MORE, THINNER individual strands is generally:

More flexible
Less flexible
Unable to carry any current
Always rated for higher voltage

Question 23: Using a conductor that is too small for the current it must carry is dangerous mainly because it can:

Overheat, potentially damaging insulation or starting a fire
Instantly stop conducting any current at all
Turn into an insulator permanently
Have no real safety consequence

Question 24: Among common electrical conductor materials, silver is actually a slightly BETTER conductor than copper, but copper is used far more often mainly because:

Copper offers an excellent balance of conductivity, cost, and availability
Silver cannot conduct electricity at all
Copper conducts better than silver in every case
There is no cost difference between silver and copper

Question 25: One practical concern with aluminum conductor terminations (at a conceptual level, not a specific product) is that aluminum:

Expands and contracts more than copper with temperature changes, which can loosen connections over time if not properly addressed
Never changes size with temperature at all
Is immune to any connection problems whatsoever
Cannot be terminated using any method

EXAM CARD BASIC

Questions25

Time limit38 min

Pass score75%

Code editionNEC 2023

DifficultyIntermediate

Last reviewedJun 2026

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Source: NEC 2026 (NFPA 70)