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NEC 2020 Code Questions Practice Test 20

Free NEC 2020 practice test with 30 questions on appliances, emergency lighting, transformers, and general NEC rules. Plain-English questions with full explanations.

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This NEC 2020 Code Questions Practice Test 20 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: Mixed-format test — questions jump between topics just like the real exam. Don't spend more than 90 seconds on any one question.

Topics covered: All NEC chapters — branch circuits, grounding, conductors, wiring methods, motors, and more.
Passing score: Aim for 80%+ consistently before scheduling your exam.
Questions: 30 multiple-choice, one correct answer each

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45 min

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NEC 2020 Code Questions Practice Test 20 — Question List

Question 1: Which organization publishes the National Electrical Code (NEC)?

NFPA
OSHA
IEEE
A state government

NEC Reference: NEC Article 90

Question 2: The NEC is normally revised and republished every:

1 year
3 years
5 years
10 years

NEC Reference: NEC Article 90

Question 3: The main purpose of the NEC is the practical safeguarding of:

Persons and property
Only equipment cost
Only appearance
Nothing specific

NEC Reference: NEC 90.1(A)

Question 4: A GFCI device protects people mainly against:

Electric shock
Low water pressure
Overheated engines
Loud noise

NEC Reference: NEC Article 100

Question 5: An AFCI device is mainly designed to reduce the risk of:

Electrical fires from arcing
Water damage
Low voltage only
Noise complaints

NEC Reference: NEC Article 100

Question 6: A grounding electrode conductor should be installed in:

One continuous length, if practical
Many small pieces, always
Only twisted wire scraps
It does not matter

NEC Reference: NEC 250.64(A)

Question 7: Equipment that will be used as service equipment must be marked as:

Suitable for use as service equipment
For decoration only
Not for electrical use
No marking is needed

NEC Reference: NEC 230.66

Question 8: A motor has a full-load current of 40 amperes. What is the minimum branch-circuit conductor ampacity?

40 amperes
45 amperes
50 amperes
60 amperes

NEC Reference: NEC 430.22(A)

Question 9: Exposed runs of NM cable must be installed to protect against:

Physical damage
Bright light only
Low humidity
It needs no protection

NEC Reference: NEC 334.15

Question 10: Each commercial building or occupancy accessible to pedestrians must have a sign outlet supplied by a branch circuit rated at least:

15 amperes
20 amperes
30 amperes
50 amperes

NEC Reference: NEC 600.5(A)

Question 11: Emergency illumination for a building's exit path is intended to help occupants:

Exit safely during a power failure
Save on the electric bill
Decorate the building
It has no real purpose

NEC Reference: NEC 700.16

Question 12: The disconnecting means for an elevator must be marked to show:

What equipment it controls
The installer's favorite color
Nothing, marking is optional
The building's square footage

NEC Reference: NEC 620.51(D)

Question 13: A wall-mounted range hood may be cord-and-plug connected if the cord length is within:

6 to 12 inches
18 to 36 inches
48 to 60 inches
Any length

NEC Reference: NEC 422.16(B)(4)

Question 14: A built-in dishwasher may be cord-and-plug connected if the cord length, measured from the front, is:

3 to 4 feet
6 to 8 inches
10 to 15 feet
Any length

NEC Reference: NEC 422.16(B)(1)

Question 15: A water heater draws 20 amperes and is treated as a continuous load. What is the minimum branch-circuit conductor ampacity?

20 amperes
25 amperes
30 amperes
40 amperes

NEC Reference: NEC 422.10(A)

Question 16: When a transformer has overcurrent protection on both the primary and secondary sides, the allowed protection settings are generally:

Higher than primary-only protection allows
Always zero
The same in every case, no difference
Not addressed by the NEC

NEC Reference: NEC Table 450.3(B)

Question 17: Full-load current values for three-phase motors are found in:

NEC Table 430.250
NEC Table 220.12
NEC Table 250.66
No table lists this

NEC Reference: NEC Table 430.250

Question 18: A service mast supporting service-drop conductors must be of adequate strength or supported by:

Braces or guy wires
Nothing extra, ever
A garden trellis
Tape

NEC Reference: NEC 230.28

Question 19: The receptacle spacing rules of NEC 210.52 apply to each dwelling unit in a two-family home:

The same way as a one-family home
Not at all
Only for the first unit
Only in the basement

NEC Reference: NEC 210.52

Question 20: If a building has a ground rod, a water pipe electrode, and a concrete-encased electrode, what must happen to all three?

They must all be bonded together
Only the best one is used
They must stay separate
Two must be removed

NEC Reference: NEC 250.50

Question 21: Lighting and appliance branch-circuit panelboards must be provided with overcurrent protection not greater than the panelboard rating, with an exception for:

Specific listed exceptions
No exceptions exist at all
Every panelboard, with no rule
Only outdoor panels

NEC Reference: NEC 408.54

Question 22: For most general wiring, the smallest copper conductor permitted is:

18 AWG
14 AWG
10 AWG
8 AWG

NEC Reference: NEC 310.4

Question 23: A motor installed in a Class I, Division 1 hazardous location must generally be:

Explosion-proof or identified for the location
A standard open motor with no protection
Not permitted at all, ever
Made of wood

NEC Reference: NEC 501.125

Question 24: Each grounded (neutral) conductor in a panelboard should terminate at:

Its own individual terminal
Any shared terminal, no limit
No terminal, twisted together loosely
It does not matter

NEC Reference: NEC 408.41

Question 25: A dwelling feeder disconnect is rated 100 amperes. Using the 83% rule, what is the minimum feeder conductor ampacity?

70 amperes
83 amperes
90 amperes
100 amperes

NEC Reference: NEC 310.12

Question 26: For circuit sizing, a fixed storage water heater of 120 gallons or less counts as a:

Continuous load
Momentary load
It is exempt from load rules
A non-continuous load, always

NEC Reference: NEC 422.13

Question 27: Generators must be protected against overload by:

Overcurrent devices or inherent design
No protection is ever required
A padlock only
A fire extinguisher only

NEC Reference: NEC 445.12

Question 28: Sufficient working space must be provided and maintained around electrical equipment to permit:

Safe operation and maintenance
Storage of tools only
Nothing, it has no purpose
Extra parking

NEC Reference: NEC 110.26(A)

Question 29: Emergency power sources should be installed to reduce the chance that a single event, such as a fire, will disable both normal and emergency power at the same time. This is a rule about:

Emergency source reliability
Paint color
Nothing important
Sound levels only

NEC Reference: NEC 700.12

Question 30: If storage batteries power an emergency system, they must generally supply the load for at least:

30 minutes
1 1/2 hours
4 hours
24 hours

NEC Reference: NEC 700.12

NEC 2020 Code Questions Practice Test 20

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NEC 2020 Code Questions Practice Test 20

How this test works

How to Use This Practice Test

Student Reviews

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NEC 2020 Code Questions Practice Test 20 — Question List

Question 1: Which organization publishes the National Electrical Code (NEC)?

Question 2: The NEC is normally revised and republished every:

Question 3: The main purpose of the NEC is the practical safeguarding of:

Question 4: A GFCI device protects people mainly against:

Question 5: An AFCI device is mainly designed to reduce the risk of:

Question 6: A grounding electrode conductor should be installed in:

Question 7: Equipment that will be used as service equipment must be marked as:

Question 8: A motor has a full-load current of 40 amperes. What is the minimum branch-circuit conductor ampacity?

Question 9: Exposed runs of NM cable must be installed to protect against:

Question 10: Each commercial building or occupancy accessible to pedestrians must have a sign outlet supplied by a branch circuit rated at least:

Question 11: Emergency illumination for a building's exit path is intended to help occupants:

Question 12: The disconnecting means for an elevator must be marked to show:

Question 13: A wall-mounted range hood may be cord-and-plug connected if the cord length is within:

Question 14: A built-in dishwasher may be cord-and-plug connected if the cord length, measured from the front, is:

Question 15: A water heater draws 20 amperes and is treated as a continuous load. What is the minimum branch-circuit conductor ampacity?

Question 16: When a transformer has overcurrent protection on both the primary and secondary sides, the allowed protection settings are generally:

Question 17: Full-load current values for three-phase motors are found in:

Question 18: A service mast supporting service-drop conductors must be of adequate strength or supported by:

Question 19: The receptacle spacing rules of NEC 210.52 apply to each dwelling unit in a two-family home:

Question 20: If a building has a ground rod, a water pipe electrode, and a concrete-encased electrode, what must happen to all three?

Question 21: Lighting and appliance branch-circuit panelboards must be provided with overcurrent protection not greater than the panelboard rating, with an exception for:

Question 22: For most general wiring, the smallest copper conductor permitted is:

Question 23: A motor installed in a Class I, Division 1 hazardous location must generally be:

Question 24: Each grounded (neutral) conductor in a panelboard should terminate at:

Question 25: A dwelling feeder disconnect is rated 100 amperes. Using the 83% rule, what is the minimum feeder conductor ampacity?

Question 26: For circuit sizing, a fixed storage water heater of 120 gallons or less counts as a:

Question 27: Generators must be protected against overload by:

Question 28: Sufficient working space must be provided and maintained around electrical equipment to permit:

Question 29: Emergency power sources should be installed to reduce the chance that a single event, such as a fire, will disable both normal and emergency power at the same time. This is a rule about:

Question 30: If storage batteries power an emergency system, they must generally supply the load for at least:

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