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NEC CODE NEC 2020

Wiring Methods (NEC 300) — NEC 2020 Edition

Free NEC 2020 practice test on general wiring methods. Covers conductors grouped together, raceway fill rules, direct burial depths, physical protection from nails and screws, and electrical continuity. 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).

How to Use This Practice Test

This Wiring Methods (NEC 300) — NEC 2020 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.
Passing score: Aim for 80%+ on NEC code tests before exam day.
Questions: 30 multiple-choice, one correct answer each

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Wiring Methods (NEC 300) — NEC 2020 Edition — Question List

Question 1: True or false: all conductors of a circuit must generally be installed in the same raceway, cable, cord, or trench.

True
False
Only for 3-phase circuits
Only outdoors

NEC Reference: NEC 300.3(B)

Question 2: Grouping all conductors of a circuit together in the same raceway is intended mainly to do what?

Minimize induction heating
Reduce fault current
Make maintenance easier only
It has no real purpose

NEC Reference: NEC 300.3(B) / 250.4(A)(3)

Question 3: Under what condition can conductors from different circuits share the same raceway?

Insulation rating is not less than the max circuit voltage
Insulation rating is less than the max circuit voltage
The circuits share the exact same voltage
The circuits share the exact same insulation rating

NEC Reference: NEC 300.3(C)(1)

Question 4: What is the minimum cover depth generally required for a direct-buried rigid nonmetallic (PVC) conduit?

18 inch
6 inch
12 inch
24 inch

NEC Reference: NEC Table 300.5

Question 5: Direct-buried cables and conductors emerging from grade must generally be protected up to what height above ground?

NEC Reference: NEC Table 300.5

Question 6: Which type of buried conductors, when 18 inches or more below grade, generally need a warning ribbon placed in the trench above them?

Service conductors
Branch circuit conductors
Feeder circuit conductors
None require a ribbon

NEC Reference: NEC 300.5(D)(3)

Question 7: True or false: raceways can generally be used as a means of support for other raceways, cables, and cords.

True
False
Only in commercial buildings
Only underground

NEC Reference: NEC 300.11

Question 8: True or false: electrical continuity should be maintained between metal raceways, cables, boxes, and fittings so they form a continuous, low-impedance fault-current path.

True
False
Only for PVC raceways
Only for underground raceways

NEC Reference: NEC 250.4(A)(3)

Question 9: A 3-wire, single-phase, 120/240V multiwire circuit supplies a 120-volt, 2,400-watt hair dryer. What is the resistance of the hair dryer?

6 ohms
20 ohms
2 ohms
4 ohms

NEC Reference: General electrical theory (Ohm's Law)

Question 10: Where cables or raceways run parallel to framing members, the nearest outside surface must generally be at least how far from the nearest edge, unless protected by a steel plate?

1 inch
1 1/4 inches
1 1/2 inches
2 inches

NEC Reference: NEC 300.4(D)

Question 11: A cable is run through a bored hole in a wood framing member. Per NEC 300.4(A)(1), the hole must generally be located at least how far from the nearest edge, or protected by a steel plate?

1 1/4 inches
1/2 inch
2 1/2 inches
3 inches

NEC Reference: NEC 300.4(A)(1)

Question 12: Direct-buried service conductors, not encased in concrete and not under a building, generally require what minimum burial depth per NEC Table 300.5, absent any special exceptions?

24 inches
6 inches
12 inches
36 inches

NEC Reference: NEC Table 300.5

Question 13: Where a raceway or cable penetrates a fire-rated wall, floor, or ceiling assembly, what must generally be done at the penetration?

Firestop to maintain the fire rating
Nothing extra is required
Leave a large open gap
Fill with sand only

NEC Reference: NEC 300.21

Question 14: Can a properly installed metal raceway, such as rigid metal conduit, serve as the equipment grounding conductor?

Yes, if properly installed
No, never
Only for underground raceways
Only for PVC raceways

NEC Reference: NEC 250.118

Question 15: Where multiple systems of different voltages are installed in a building, what must be done to help identify the different systems' conductors?

Identify each system distinctly, such as by color
Nothing -- mixing is fine with no marking
Use the same color for everything
Remove all labels

NEC Reference: NEC 210.5(C)

Question 16: Are wiring methods generally permitted to be installed inside ducts used to transport dust, loose stock, or flammable vapors?

No, this is generally prohibited
Yes, always permitted freely
Only for PVC wiring
Only in residential buildings

NEC Reference: NEC 300.22(A)

Question 17: Metal raceways must generally be mechanically continuous between what points?

Cabinets, boxes, fittings, and enclosures
Nothing -- gaps are fine
Only at the service
Only underground

NEC Reference: NEC 300.12

Question 18: Raceways must generally be securely fastened in place, and supported, per what general rule?

Securely fastened and supported
Left loose and unsupported
Supported only once a year
Nothing is required

NEC Reference: NEC 300.11

Question 19: Wiring installed in hoistways and elevator shafts is generally restricted to circuits associated with what?

The elevator equipment itself
Any unrelated building circuit
Nothing is restricted
Only telephone wiring

NEC Reference: NEC 300.21 / 620.21

Question 20: Where a nonmetallic-sheathed cable passes through a factory- or field-punched hole in a metal framing member, what is generally required?

A listed bushing or grommet
Nothing -- the bare metal edge is fine
Duct tape only
A steel plate always, even with a bushing

NEC Reference: NEC 300.4(B)(1)

Question 21: Conductors installed in a vertical raceway must generally be supported at specific intervals to prevent what?

Insulation and termination damage from excess weight/strain
Nothing -- support is not needed vertically
Overheating from sunlight
Rodent damage only

NEC Reference: NEC 300.19

Question 22: Conductor splices and taps must generally be made where?

Within an accessible box or approved enclosure
Buried directly in the wall with no box
Inside a wall cavity with no access
Anywhere, with no restriction

NEC Reference: NEC 300.15

Question 23: Wiring methods installed in wet locations must generally be what?

Suitable for wet locations
Made of any material, no restriction
Always removed before rain
Nothing special is required

NEC Reference: NEC 300.6

Question 24: For 3 or more conductors in a raceway, what is the maximum fill percentage generally permitted, per NEC Chapter 9, Table 1?

NEC Reference: NEC Chapter 9, Table 1

Question 25: A long run of PVC conduit needs an expansion fitting when the expected length change from temperature is more than what?

1/4 inch
2 inches
6 inches
1 foot

NEC Reference: NEC 352.44

Question 26: A cable is run through a notch cut into the edge of a wood framing member. What is generally required to protect it?

A steel plate at least 1/16 inch thick
Nothing is required
Duct tape only
Paint over the notch

NEC Reference: NEC 300.4(A)(2)

Question 27: Exposed cable installed on a surface, where subject to physical damage, must generally be what?

Protected, such as with conduit or guard strips
Left completely exposed with no protection
Painted a bright color only
Nothing is required

NEC Reference: NEC 300.4

Question 28: Raceways entering a building from an underground distribution system must generally be sealed to prevent what?

Moisture or gases entering the building
Nothing -- sealing is unnecessary
Only insects
Only sunlight

NEC Reference: NEC 300.5(G)

Question 29: Conductors installed in any wiring method must generally have an insulation rating suitable for what?

The voltage, temperature, and location
Nothing -- any insulation works anywhere
Only the conductor color
Only the manufacturer's preference

NEC Reference: NEC 310.10(A)

Question 30: A wiring method not specifically covered elsewhere in the NEC may generally be used if what condition is met?

It is approved by the authority having jurisdiction
It is never allowed under any circumstance
It requires no approval at all
It is chosen randomly by the installer

NEC Reference: NEC 300.1 / 90.4

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.

Wiring Methods (NEC 300) — NEC 2020 Edition

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Key NEC References for This Test

Wiring Methods (NEC 300) — NEC 2020 Edition

How this test works

Frequently Asked Questions

Is this Wiring Methods (NEC 300) — NEC 2020 Edition free?

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Which NEC edition should I study?

What articles are covered on electrician licensing exams?

How to Use This Practice Test

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Wiring Methods (NEC 300) — NEC 2020 Edition — Question List

Question 1: True or false: all conductors of a circuit must generally be installed in the same raceway, cable, cord, or trench.

Question 2: Grouping all conductors of a circuit together in the same raceway is intended mainly to do what?

Question 3: Under what condition can conductors from different circuits share the same raceway?

Question 4: What is the minimum cover depth generally required for a direct-buried rigid nonmetallic (PVC) conduit?

Question 5: Direct-buried cables and conductors emerging from grade must generally be protected up to what height above ground?

Question 6: Which type of buried conductors, when 18 inches or more below grade, generally need a warning ribbon placed in the trench above them?

Question 7: True or false: raceways can generally be used as a means of support for other raceways, cables, and cords.

Question 8: True or false: electrical continuity should be maintained between metal raceways, cables, boxes, and fittings so they form a continuous, low-impedance fault-current path.

Question 9: A 3-wire, single-phase, 120/240V multiwire circuit supplies a 120-volt, 2,400-watt hair dryer. What is the resistance of the hair dryer?

Question 10: Where cables or raceways run parallel to framing members, the nearest outside surface must generally be at least how far from the nearest edge, unless protected by a steel plate?

Question 11: A cable is run through a bored hole in a wood framing member. Per NEC 300.4(A)(1), the hole must generally be located at least how far from the nearest edge, or protected by a steel plate?

Question 12: Direct-buried service conductors, not encased in concrete and not under a building, generally require what minimum burial depth per NEC Table 300.5, absent any special exceptions?

Question 13: Where a raceway or cable penetrates a fire-rated wall, floor, or ceiling assembly, what must generally be done at the penetration?

Question 14: Can a properly installed metal raceway, such as rigid metal conduit, serve as the equipment grounding conductor?

Question 15: Where multiple systems of different voltages are installed in a building, what must be done to help identify the different systems' conductors?

Question 16: Are wiring methods generally permitted to be installed inside ducts used to transport dust, loose stock, or flammable vapors?

Question 17: Metal raceways must generally be mechanically continuous between what points?

Question 18: Raceways must generally be securely fastened in place, and supported, per what general rule?

Question 19: Wiring installed in hoistways and elevator shafts is generally restricted to circuits associated with what?

Question 20: Where a nonmetallic-sheathed cable passes through a factory- or field-punched hole in a metal framing member, what is generally required?

Question 21: Conductors installed in a vertical raceway must generally be supported at specific intervals to prevent what?

Question 22: Conductor splices and taps must generally be made where?

Question 23: Wiring methods installed in wet locations must generally be what?

Question 24: For 3 or more conductors in a raceway, what is the maximum fill percentage generally permitted, per NEC Chapter 9, Table 1?

Question 25: A long run of PVC conduit needs an expansion fitting when the expected length change from temperature is more than what?

Question 26: A cable is run through a notch cut into the edge of a wood framing member. What is generally required to protect it?

Question 27: Exposed cable installed on a surface, where subject to physical damage, must generally be what?

Question 28: Raceways entering a building from an underground distribution system must generally be sealed to prevent what?

Question 29: Conductors installed in any wiring method must generally have an insulation rating suitable for what?

Question 30: A wiring method not specifically covered elsewhere in the NEC may generally be used if what condition is met?

Key NEC References for This Test

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