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Flexible Cords and Fixture Wires (NEC 400/402) — NEC 2023 Edition

Free NEC 2023 practice test on flexible cords and fixture wires. Covers permitted and prohibited uses of flexible cords, ampacity adjustment for grouped conductors, overcurrent protection, and fixture wire sizing. Simple English, full explanations.

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The National Electrical Code (NFPA 70) is the benchmark standard for safe electrical installation in the US. It is updated every 3 years by the NFPA.

Study the edition adopted by your state. As of 2025, most states use the 2020 or 2023 NEC. These tests are written to the 2023 edition.

The most tested articles are 100 (Definitions), 200–250 (Wiring & Grounding), 300–314 (Wiring Methods), 400–411 (Conductors), 430 (Motors), and 700–701 (Emergency Systems).

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This Flexible Cords and Fixture Wires (NEC 400/402) — NEC 2023 Edition has 30 questions with detailed answers and NEC references. Take the full test, review every wrong answer, and look up the NEC article it references before moving on.

Tip: Use the NEC index (back of the book) — find answers by keyword, not by article number.

Topics covered: NEC articles 100, 210, 220, 240, 250, 300, 310, 430, and special occupancies.
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Questions: 30 multiple-choice, one correct answer each

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Flexible Cords and Fixture Wires (NEC 400/402) — NEC 2023 Edition — Question List

Question 1: Flexible cord may NOT be used as a substitute for what?

The wiring of a crane or hoist
The fixed wiring of a structure
A pendant for a luminaire
A cord for a portable appliance

NEC Reference: NEC 400.12

Question 2: Eight 16-ampere current-carrying conductors are grouped together in a flexible cord. What is the allowable ampacity of each conductor after adjustment?

11.2 amperes
16 amperes
12.8 amperes
14.4 amperes

NEC Reference: NEC Table 400.5(A)(3)

Question 3: In which of the following situations is a flexible cord generally NOT permitted to be used?

Wiring of cranes and hoists
Connection of moving parts
Elevator cables
Attached to building surfaces

NEC Reference: NEC 400.12

Question 4: Flexible cord is protected against overcurrent in accordance with its ampacity from which table?

Table 310.16
Table 400.4
Table 402.5
Table 400.5(A)(1) and Table 400.5(A)(2)

NEC Reference: NEC 240.5(A)

Question 5: What is the minimum size fixture wire generally permitted for wiring control circuits?

18 AWG
16 AWG
10 AWG
12 AWG

NEC Reference: NEC 402.6

Question 6: What is the allowable ampacity of a 10 AWG fixture wire?

NEC Reference: NEC Table 402.5

Question 7: Unless specifically permitted, fixture wires cannot generally be used for which type of wiring?

Branch circuit wiring
Elevator and escalator control circuits
To connect luminaires
Fire alarm circuits

NEC Reference: NEC 402.11

Question 8: When 5 current-carrying conductors are grouped together in a flexible cord, what percent of the rated ampacity is allowed for each conductor?

NEC Reference: NEC Table 400.5(A)(3)

Question 9: Which of the following IS a permitted use of flexible cord, per NEC 400.10?

Pendant luminaires
Fixed permanent wiring in walls
Underground burial
Concealed within concrete

NEC Reference: NEC 400.10(A)

Question 10: What information must be marked on flexible cords (by tag, or on the surface of types such as S, SO and ST)?

Type designation, size and number of conductors
The ampacity at 30 °C and length
Only the manufacturer's name
The installation date and circuit number

NEC Reference: NEC 400.6

Question 11: Flexible cord installed in an application permitted by 400.10(A) must generally be installed how?

In continuous lengths without splice or tap
With splices allowed in any size of cord
With splices made only with tape
With taps every 10 ft

NEC Reference: NEC 400.13

Question 12: Where flexible cord passes through a hole in an outlet box cover or similar enclosure, how must it be protected?

With a larger hole only
With a cord grip on the outside only
With bushings or fittings
With electrical tape wrapped around the cord

NEC Reference: NEC 400.17

Question 13: A flexible cord has three current-carrying conductors. What ampacity adjustment factor from Table 400.5(A)(3) applies?

70%
80%
50%
None (100%), since the table starts at 4 conductors

NEC Reference: NEC 400.5(A)

Question 14: Besides the insulation type, what key characteristic does Table 402.3 list for each fixture wire type?

Maximum length of run
Maximum operating temperature
Number of strands
Ampacity at 60 °C

NEC Reference: NEC Table 402.3

Question 15: In a flexible cord, the grounded (neutral) conductor is generally identified by what color or marking?

White, gray, or another approved marking
Always bright orange
No marking is ever used
Always black

NEC Reference: NEC 400.22

Question 16: Extension cords used on a construction site are generally covered under which special NEC article, in addition to Article 400?

Article 590 (temporary wiring)
Article 250 only
Article 90 only
No article covers this

NEC Reference: NEC Article 590

Question 17: Fixture wires generally range in size from 18 AWG up to what maximum size, per NEC Article 402?

10 AWG
6 AWG
2 AWG
1/0 AWG

NEC Reference: NEC Article 402

Question 18: What do service classifications such as "hard usage" and "extra-hard usage" in Table 400.4 tell you about a flexible cord?

Its maximum voltage only
Its color code
Its conductor material
How rugged it is for the physical conditions of use

NEC Reference: NEC Table 400.4

Question 19: The ampacity of a flexible cord in Table 400.5(A)(1) depends on its conductor size and what else?

The length of the cord
The color of the outer jacket
The number of current-carrying conductors (column A, B or C)
The brand of the cord

NEC Reference: NEC 400.5(A)

Question 20: How must a fixture wire used as a grounded conductor be identified?

By a red tracer
By one or more continuous white stripes or other means of 400.22
By green insulation
It needs no identification

NEC Reference: NEC 402.8

Question 21: Where flexible cord is used to connect portable equipment or to allow removal for maintenance, what must the cord be equipped with?

An attachment plug, energized from a receptacle or cord connector
A strain relief clamp only
A separate disconnect switch
A splice box at each end

NEC Reference: NEC 400.10(B)

Question 22: Flexible cords must be connected so that tension is not transmitted to joints or terminal screws. Which method is recognized?

Soldering the conductors to the terminals
Using a larger terminal screw
Leaving extra slack coiled inside the box
Knotting the cord, winding with tape, or fittings designed for the purpose

NEC Reference: NEC 400.14

Question 23: What is the allowable ampacity of a 12 AWG fixture wire according to Table 402.5?

17 amperes
20 amperes
23 amperes
25 amperes

NEC Reference: NEC Table 402.5

Question 24: Which of these flexible cord installations is prohibited by 400.12?

Connecting a portable appliance
Wiring a crane or hoist
Running the cord through a hole in the floor to a receptacle below
Supplying a pendant luminaire

NEC Reference: NEC 400.12

Question 25: Extension cords on a construction site are plugged into 125-volt, single-phase, 15-, 20- and 30-ampere receptacle outlets. What protection must those outlets have?

Surge protection only
GFCI protection for personnel
No protection beyond the breaker
AFCI protection

NEC Reference: NEC 590.6(A)(1)

Question 26: A cord-and-plug-connected appliance requires grounding. What must its flexible cord include?

An equipment grounding conductor
A shield drain wire
A second grounded conductor
A larger ungrounded conductor

NEC Reference: NEC 250.138(A)

Question 27: On a polarized attachment plug, the identified (grounded) conductor of the cord must connect to which terminal?

The green hex-head terminal
The terminal that is white or silver in color
The brass-colored terminal
The terminal with the largest screw

NEC Reference: NEC 200.10(B)

Question 28: May flexible cord be installed above a suspended (dropped) ceiling to reach a luminaire?

No, 400.12 prohibits cord located above suspended or dropped ceilings
Yes, if the cord is secured to the ceiling grid
Yes, if it is no longer than 6 ft
Yes, if the cord is plenum rated

NEC Reference: NEC 400.12

Question 29: Why must the fixture wire type selected from Table 402.3 suit the luminaire?

It must be solid, never stranded
It must be the same brand as the luminaire
It must withstand the operating temperature inside the luminaire
It must match the luminaire color

NEC Reference: NEC Table 402.3

Question 30: Which flexible cord type is classified for extra-hard usage in Table 400.4?

Type SPT-2
Type HPN
Type SJ
Type SO

NEC Reference: NEC Table 400.4

Key NEC References for This Test

Article	What It Covers
Ch. 1–4	General rules — apply to all installations
Ch. 5–7	Special rules — override Ch. 1–4 where they conflict
Ch. 8	Communications — completely independent of Ch. 1–7
Ch. 9	Tables — referenced by articles, not standalone enforceable rules
Art. 210.12	AFCI — major expansion in NEC 2026
Art. 230.67	Surge protection at service equipment — new NEC 2026

Study Tip: Learn the NEC index — use keywords, not article numbers. Practice finding 5 different topics in under 2 minutes each.

Flexible Cords and Fixture Wires (NEC 400/402) — NEC 2023 Edition

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Flexible Cords and Fixture Wires (NEC 400/402) — NEC 2023 Edition

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Flexible Cords and Fixture Wires (NEC 400/402) — NEC 2023 Edition — Question List

Question 1: Flexible cord may NOT be used as a substitute for what?

Question 2: Eight 16-ampere current-carrying conductors are grouped together in a flexible cord. What is the allowable ampacity of each conductor after adjustment?

Question 3: In which of the following situations is a flexible cord generally NOT permitted to be used?

Question 4: Flexible cord is protected against overcurrent in accordance with its ampacity from which table?

Question 5: What is the minimum size fixture wire generally permitted for wiring control circuits?

Question 6: What is the allowable ampacity of a 10 AWG fixture wire?

Question 7: Unless specifically permitted, fixture wires cannot generally be used for which type of wiring?

Question 8: When 5 current-carrying conductors are grouped together in a flexible cord, what percent of the rated ampacity is allowed for each conductor?

Question 9: Which of the following IS a permitted use of flexible cord, per NEC 400.10?

Question 10: What information must be marked on flexible cords (by tag, or on the surface of types such as S, SO and ST)?

Question 11: Flexible cord installed in an application permitted by 400.10(A) must generally be installed how?

Question 12: Where flexible cord passes through a hole in an outlet box cover or similar enclosure, how must it be protected?

Question 13: A flexible cord has three current-carrying conductors. What ampacity adjustment factor from Table 400.5(A)(3) applies?

Question 14: Besides the insulation type, what key characteristic does Table 402.3 list for each fixture wire type?

Question 15: In a flexible cord, the grounded (neutral) conductor is generally identified by what color or marking?

Question 16: Extension cords used on a construction site are generally covered under which special NEC article, in addition to Article 400?

Question 17: Fixture wires generally range in size from 18 AWG up to what maximum size, per NEC Article 402?

Question 18: What do service classifications such as "hard usage" and "extra-hard usage" in Table 400.4 tell you about a flexible cord?

Question 19: The ampacity of a flexible cord in Table 400.5(A)(1) depends on its conductor size and what else?

Question 20: How must a fixture wire used as a grounded conductor be identified?

Question 21: Where flexible cord is used to connect portable equipment or to allow removal for maintenance, what must the cord be equipped with?

Question 22: Flexible cords must be connected so that tension is not transmitted to joints or terminal screws. Which method is recognized?

Question 23: What is the allowable ampacity of a 12 AWG fixture wire according to Table 402.5?

Question 24: Which of these flexible cord installations is prohibited by 400.12?

Question 25: Extension cords on a construction site are plugged into 125-volt, single-phase, 15-, 20- and 30-ampere receptacle outlets. What protection must those outlets have?

Question 26: A cord-and-plug-connected appliance requires grounding. What must its flexible cord include?

Question 27: On a polarized attachment plug, the identified (grounded) conductor of the cord must connect to which terminal?

Question 28: May flexible cord be installed above a suspended (dropped) ceiling to reach a luminaire?

Question 29: Why must the fixture wire type selected from Table 402.3 suit the luminaire?

Question 30: Which flexible cord type is classified for extra-hard usage in Table 400.4?

Key NEC References for This Test

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