Previous NEC 2020 Code Questions Practice Test 14 Next NEC 2020 Code Questions Practice Test 16

NEC_PRACTICE NEC 2020

NEC 2020 Code Questions Practice Test 15

Free NEC 2020 practice test with 30 questions on grounding electrodes, bonding jumpers, panelboards, and box fill. Plain-English questions with full explanations.

TOPICS COVERED

NEC Practice Tests

How this test works

Read each question carefully

Look for absolute words like always / never — they often distinguish the right answer.

Manage your time

You have 45 min for 30 questions. Skip tough ones and come back.

Progress is auto-saved

Your answers are saved locally — a page refresh won't lose your work.

Review your answers

After submitting you'll see every explanation and your NEC references.

How to Use This Practice Test

This NEC 2020 Code Questions Practice Test 15 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

Questions

45 min

Time

70%

Pass

Timer starts immediately. Progress is auto-saved.

NEC 2020 Code Questions Practice Test 15 — Question List

Question 1: A concrete-encased electrode (Ufer ground) needs at least 20 feet of steel rebar or bare copper wire, covered by at least how much concrete?

2 inches
1/4 inch
12 inches
No cover is stated

NEC Reference: NEC 250.52(A)(3)

Question 2: A metal underground water pipe can be used as a grounding electrode if it is in contact with the earth for at least:

2 feet
10 feet
50 feet
Any length

NEC Reference: NEC 250.52(A)(1)

Question 3: When a second (supplemental) ground rod is installed, it must be spaced from the first rod by at least:

2 feet
6 feet
10 feet
20 feet

NEC Reference: NEC 250.53(A)(3)

Question 4: A single ground rod tests at 30 ohms resistance to earth. What must be done?

Add a supplemental electrode
Nothing further is needed
Remove the rod completely
Shut off the whole service

NEC Reference: NEC 250.53(A)(2)

Question 5: Where the grounding electrode conductor connects only to a ground rod, it need not be larger than:

6 AWG copper
2/0 AWG copper
14 AWG copper
There is no limit

NEC Reference: NEC 250.66(A)

Question 6: A metal raceway that holds a grounding electrode conductor must be:

Bonded at both ends
Left ungrounded
Insulated from the conductor
Not permitted at all

NEC Reference: NEC 250.86

Question 7: Metal ductwork that could become energized must be bonded to:

The service equipment or grounding system
It is never bonded
A tree root
The phone company

NEC Reference: NEC 250.104(C)

Question 8: Metal gas piping that could become energized must be bonded to:

The service equipment or grounding system
Nothing, gas pipe is never bonded
Only the gas meter
The telephone line

NEC Reference: NEC 250.104(B)

Question 9: The grounded (neutral) conductor must be run to each service disconnect and:

Bonded to the disconnect
Left disconnected
Cut short
Removed entirely

NEC Reference: NEC 250.24(C)

Question 10: Where several service disconnects share one set of service conductors, the grounded conductor must connect to the grounding electrode system at:

Only one point
Every disconnect separately
It does not matter
No connection is made

NEC Reference: NEC 250.24(A)(4)

Question 11: Past the service disconnect, the neutral conductor is generally not permitted to be used to:

Ground equipment
Carry any current
Connect to the panel
It has no such rule

NEC Reference: NEC 250.142(B)

Question 12: For a transformer that creates a separately derived system, the system bonding jumper goes at the source or at:

The first disconnect, but not both places
Every downstream panel
It is never required
The far end of the circuit only

NEC Reference: NEC 250.30(A)

Question 13: Which of the following is an approved way to make a grounding connection?

Exothermic welding
Solder alone
Tape alone
No method is approved

NEC Reference: NEC 250.8

Question 14: Every panelboard must be marked by the maker with the voltage, current rating, and:

Number of phases
The buyer's address
No marking is required
The store name

NEC Reference: NEC 408.30

Question 15: Panelboard circuits must be arranged so they do not overload the:

Supply conductors or bus
Building foundation
Owner's budget
Nothing, arrangement does not matter

NEC Reference: NEC 408.3(A)

Question 16: For box fill, a switch or receptacle on one strap counts as how many conductors?

Zero
One
Two
Four

NEC Reference: NEC 314.16(B)(4)

Question 17: When a box has one or more internal cable clamps, the fill calculation must add:

One conductor allowance
One allowance per clamp
Zero, clamps are not counted
Four conductor allowances

NEC Reference: NEC 314.16(B)(3)

Question 18: When several equipment grounding conductors enter a box, they are counted in the fill calculation as:

One conductor total
Each one counted separately
Never counted
Two conductors, always

NEC Reference: NEC 314.16(B)(2)

Question 19: In a wall made of wood, an outlet box must be flush or set back from the surface by no more than:

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

NEC Reference: NEC 314.20

Question 20: For a straight pull, a pull box must be at least how many times the trade size of the largest raceway?

4 times
6 times
8 times
10 times

NEC Reference: NEC 314.28(A)(1)

Question 21: For an angle pull, the pull box distance must be at least how many times the trade size of the largest raceway?

4 times
6 times
8 times
10 times

NEC Reference: NEC 314.28(A)(2)

Question 22: Conductors entering a box must be protected from:

Abrasion
Nothing, no rule applies
Voltage drop
Sunlight

NEC Reference: NEC 314.17

Question 23: A raceway is generally not permitted to be used to support:

Other raceways or cables
Itself
Nothing, this is always allowed
Light fixtures only

NEC Reference: NEC 300.11(B)

Question 24: All conductors of the same circuit must generally be run:

Together in the same raceway or cable
In separate raceways
It does not matter
6 inches apart, always

NEC Reference: NEC 300.3(B)

Question 25: Where wiring passes through a fire-rated wall, the opening must be sealed to:

Keep the fire rating intact
Improve air flow
Save money on materials
It has no purpose

NEC Reference: NEC 300.21

Question 26: A raceway buried underground is treated as a wet location inside. The conductors used inside must be:

Listed for wet locations
Any dry-location conductor
It does not matter
Bare, with no insulation

NEC Reference: NEC 300.9

Question 27: An underground raceway entering a building must be sealed to keep out:

Moisture and gas
Sunlight only
Nothing, sealing is optional
Noise

NEC Reference: NEC 300.5(G)

Question 28: A raceway runs from a warm indoor space to the cold outdoors. It must be sealed to prevent:

Warm air moving to the cold end
Electricity from flowing
Sound
Nothing, it has no purpose

NEC Reference: NEC 300.7(A)

Question 29: A direct-buried cable can be spliced underground without a splice box, if the splice method is:

Listed for direct burial
Wrapped in tape only
Never allowed underground
Soldered only

NEC Reference: NEC 300.5(E)

Question 30: What section of the NEC covers rules for direct-buried cable, including depth and protection?

NEC 300.5
NEC 90.1
NEC 110.3
No section covers this

NEC Reference: NEC 300.5

NEC 2020 Code Questions Practice Test 15

How this test works

How to Use This Practice Test

Student Reviews

Leave a Review

NEC 2020 Code Questions Practice Test 15

How this test works

How to Use This Practice Test

Student Reviews

Leave a Review

NEC 2020 Code Questions Practice Test 15 — Question List

Question 1: A concrete-encased electrode (Ufer ground) needs at least 20 feet of steel rebar or bare copper wire, covered by at least how much concrete?

Question 2: A metal underground water pipe can be used as a grounding electrode if it is in contact with the earth for at least:

Question 3: When a second (supplemental) ground rod is installed, it must be spaced from the first rod by at least:

Question 4: A single ground rod tests at 30 ohms resistance to earth. What must be done?

Question 5: Where the grounding electrode conductor connects only to a ground rod, it need not be larger than:

Question 6: A metal raceway that holds a grounding electrode conductor must be:

Question 7: Metal ductwork that could become energized must be bonded to:

Question 8: Metal gas piping that could become energized must be bonded to:

Question 9: The grounded (neutral) conductor must be run to each service disconnect and:

Question 10: Where several service disconnects share one set of service conductors, the grounded conductor must connect to the grounding electrode system at:

Question 11: Past the service disconnect, the neutral conductor is generally not permitted to be used to:

Question 12: For a transformer that creates a separately derived system, the system bonding jumper goes at the source or at:

Question 13: Which of the following is an approved way to make a grounding connection?

Question 14: Every panelboard must be marked by the maker with the voltage, current rating, and:

Question 15: Panelboard circuits must be arranged so they do not overload the:

Question 16: For box fill, a switch or receptacle on one strap counts as how many conductors?

Question 17: When a box has one or more internal cable clamps, the fill calculation must add:

Question 18: When several equipment grounding conductors enter a box, they are counted in the fill calculation as:

Question 19: In a wall made of wood, an outlet box must be flush or set back from the surface by no more than:

Question 20: For a straight pull, a pull box must be at least how many times the trade size of the largest raceway?

Question 21: For an angle pull, the pull box distance must be at least how many times the trade size of the largest raceway?

Question 22: Conductors entering a box must be protected from:

Question 23: A raceway is generally not permitted to be used to support:

Question 24: All conductors of the same circuit must generally be run:

Question 25: Where wiring passes through a fire-rated wall, the opening must be sealed to:

Question 26: A raceway buried underground is treated as a wet location inside. The conductors used inside must be:

Question 27: An underground raceway entering a building must be sealed to keep out:

Question 28: A raceway runs from a warm indoor space to the cold outdoors. It must be sealed to prevent:

Question 29: A direct-buried cable can be spliced underground without a splice box, if the splice method is:

Question 30: What section of the NEC covers rules for direct-buried cable, including depth and protection?

Related Practice Tests