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MASTER NEC 2023

Master Electrician Practice Test - Advanced Mixed Topics

This is Master Electrician Practice Test 10 — Advanced Mixed Topics, the final test in our master electrician series. It pulls together the cross-article reasoning and applied calculations that appear throughout the master licensing exam. The test has 26 multiple-choice questions on conductor derating (temperature correction and bundling), parallel conductors, overhead service clearances, working space requirements, dedicated electrical space, high-leg delta identification, terminal temperature ratings, continuous loads, temporary wiring, and multi-building service rules. Pass score is 70%. Every question includes a full NEC 2023 explanation that shows the calculation or rule behind the correct answer.

TOPICS COVERED

Conductor Derating Continuous Loads Voltage Drop Parallel Conductors Service Clearances Services

How this test works

Read each question carefully

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

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You have 45 min for 26 questions. Skip tough ones and come back.

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

Frequently Asked Questions

Yes — completely free with no signup required. All answers include detailed explanations.

Requirements vary by state but typically include 4–8 years of documented electrical work experience plus a valid Journeyman license.

Advanced NEC code interpretation, load calculations, service entrance design, motor controls, generator systems, and electrical system design.

The Master exam focuses more on design, calculations, and planning rather than installation details. Load calculation and service sizing questions are weighted heavily.

Before You Start

26 questions — multiple choice
45 minutes to finish (timer starts when you begin)
Pass score is 70% — you need at least 19 correct answers
Full NEC 2023 explanation shown for every question after you submit

Topics in This Test

Neutral conductor as a current-carrying conductor in nonlinear 3-phase circuits (NEC 310.15(E)(1)(b))
Continuous load definition — 3 hours or more (NEC Article 100)
Temperature correction factors for elevated ambient temperature (NEC Table 310.15(B)(1))
Bundling adjustment factors — 70% for 7–9 conductors, 50% for 10+ conductors (NEC Table 310.15(C)(1))
Voltage drop recommendations — 3% branch circuit, 5% combined (NEC 210.19(A)(1) IN)
Parallel conductor minimum size — 1/0 AWG copper minimum per conductor (NEC 310.10(G)(1))
Service drop clearance over a residential driveway — 12 feet minimum (NEC 230.24(B)(1))
Service drop clearance over public streets and truck traffic — 18 feet minimum (NEC 230.24(B)(2))
Maximum number of service disconnects — six disconnects allowed (NEC 230.71(A))
Dedicated electrical space — 6 feet above top of equipment (NEC 110.26(F)(1)(a))
Working clearance for 480V Condition 2 — 3.5 feet minimum (NEC Table 110.26(A)(1))
High-leg delta identification — orange color, B phase position (NEC 230.56)
Terminal temperature rating controls conductor ampacity selection (NEC 110.14(C)(1))
Combined temperature correction and bundling derating — both applied simultaneously
Equipment manufacturer instructions — part of the listing, must be followed (NEC 110.3(B))
Service drop clearance at pedestrian entrance — 10 feet minimum (NEC 230.24(B)(1))
Temporary wiring on construction sites — physical damage protection (NEC 590.4(B))
Equipment in corrosive environments (NEC 110.11)
Overhead service clearance diagram — identifying which point violates the minimum
3-phase voltage drop formula — why the √3 factor is used
Minimum working space headroom — 6.5 feet (NEC 110.26(A)(3))
Single service per building rule and exceptions (NEC 230.2)
Foreign systems in dedicated electrical space — pipes and ducts prohibited (NEC 110.26(F)(1)(b))

Tip: When applying both a temperature correction factor and a bundling adjustment factor, multiply them together — do not add them. Then apply the combined multiplier to the base ampacity from Table 310.16.

Questions

45 min

Time

70%

Pass

Timer starts immediately. Progress is auto-saved.

Master Electrician Practice Test - Advanced Mixed Topics — Question List

Question 1: In a 3-phase, 4-wire wye system where more than 50% of the load is nonlinear (computers, VFDs, LED drivers), how is the neutral treated when counting current-carrying conductors for derating?

The neutral never counts as a current-carrying conductor
The neutral counts as a current-carrying conductor because it carries harmonic current
The neutral counts only if it is larger than the phase conductors
The neutral counts only in single-phase circuits

NEC Reference: NEC 310.15(E)(1)(b)

Question 2: The NEC defines a continuous load as a load that is expected to continue without interruption for at least:

1 hour
2 hours
3 hours
8 hours

NEC Reference: NEC Article 100 (Definitions)

Question 3: A 6 AWG THWN copper conductor (75°C rated, 65A per Table 310.16) is installed in a location where the ambient temperature is 50°C. What is the corrected ampacity?

49A — 65A × 0.75 temperature correction
54A — 65A × 0.82
58A — 65A × 0.88
65A — no correction needed below 60°C

NEC Reference: NEC Table 310.15(B)(1)

Question 4: Eight 10 AWG THWN conductors (35A ampacity each) are all installed in the same conduit, and all eight are current-carrying. What is the adjusted ampacity for each conductor?

24.5A — 35A × 0.70 (7–9 conductor factor)
28A — 35A × 0.80 (4–6 conductor factor)
31.5A — 35A × 0.90
35A — no derating needed for 10 AWG

NEC Reference: NEC Table 310.15(C)(1)

Question 5: The NEC has an informational note that recommends keeping voltage drop at or below what percentage for branch circuits, and what combined percentage for the whole system (feeder + branch)?

2% branch circuit, 3% combined
3% branch circuit, 5% combined
5% branch circuit, 8% combined
5% anywhere in the system

NEC Reference: NEC 210.19(A)(1) IN, 215.2(A)(1) IN

Question 6: When two or more conductors are installed in parallel to form a single large feeder, each individual conductor must be at least what size?

4 AWG copper — any size is fine if the total is adequate
2 AWG copper minimum for parallel conductors
1/0 AWG copper minimum per conductor
4/0 AWG copper — parallel conductors must be very large

NEC Reference: NEC 310.10(H)(1)

Question 7: Service drop conductors passing over a residential driveway must maintain a minimum clearance above the ground of:

10 feet
12 feet
15 feet
18 feet

NEC Reference: NEC 230.24(B)(1)

Question 8: Service drop conductors passing over a public street or road subject to truck traffic must maintain a minimum ground clearance of:

12 feet
15 feet
18 feet
22 feet

NEC Reference: NEC 230.24(B)(2)

Question 9: How many service disconnects are allowed per service, per 230.71?

Two
Four
Six
No limit — as many as needed

NEC Reference: NEC 230.71(A)

Question 10: The dedicated electrical space above a panelboard must extend how far above the top of the equipment?

3 ft above the top of the equipment
6 ft above the top of the equipment (or to structural ceiling)
To the highest point of the room only
No dedicated space is required above the panel

NEC Reference: NEC 110.26(F)(1)(a)

Question 11: A 480V switchboard has exposed live parts on one side of the working space and grounded metal parts on the other (Condition 2). What is the minimum working clearance depth in front of the switchboard?

3 feet
3½ feet
4 feet
6 feet

NEC Reference: NEC Table 110.26(A)(1)

Question 12: In a 120/240V, 4-wire delta service (high-leg delta), one phase has a higher voltage to ground than the other two. This phase must be identified with what color, and which phase position is it in?

Red color, A phase position
Orange color, B phase (middle) position
Yellow color, C phase position
Brown color — no specific phase position required

NEC Reference: NEC 230.56

Question 13: You install 1/0 AWG THHN conductors (90°C insulation, 170A per Table 310.16). The terminations on the panel and equipment are marked "75°C." Which ampacity column from Table 310.16 must you use?

The 90°C column — the wire is rated 90°C so that is the limiting factor
The 75°C column — the terminal rating limits you to 75°C ampacity
The 60°C column — always use the most conservative value
Either column — the higher of the two values governs

NEC Reference: NEC 110.14(C)(1)

Question 14: Five 12 AWG THWN conductors (all current-carrying) are in the same conduit. What bundling adjustment factor applies, and what is the adjusted ampacity of each conductor?

70% factor — 25A × 0.70 = 17.5A
80% factor — 25A × 0.80 = 20A
90% factor — 25A × 0.90 = 22.5A
No derating — five conductors is under the threshold

NEC Reference: NEC Table 310.15(C)(1)

Question 15: An electrician installs a motor according to all NEC rules, but the motor manufacturer instructions say to use a specific wiring method and conductor size that is more restrictive than what the NEC requires. Which takes precedence?

The NEC always overrides manufacturer instructions
The manufacturer installation instructions — they are part of the listing
Whichever is less expensive to install
The local building code, which supersedes both

NEC Reference: NEC 110.3(B)

Question 16: Service drop conductors at the point where they enter a dwelling (over a porch or walkway accessible only to pedestrians) must be at least how many feet above the ground?

8 feet
10 feet
12 feet
15 feet

NEC Reference: NEC 230.24(B)(1)

Question 17: During construction, temporary feeder cables that run on the ground across a work site must be:

Left loose on the ground — construction sites are temporary
Protected from physical damage when subject to physical damage
Buried at least 6 inches deep even for temporary runs
Installed in conduit just like permanent wiring

NEC Reference: NEC 590.4(B)

Question 18: Electrical equipment installed in a chemical storage room where the atmosphere could corrode metal parts must be:

Standard equipment — corrosion is a maintenance issue, not a code issue
Equipment approved or listed for use in the specific corrosive environment
Equipment rated NEMA 1 with a painted finish
No restriction — any equipment in a metal enclosure is acceptable

NEC Reference: NEC 110.11

Question 19: The overhead clearance diagram shows a service drop crossing over different areas. Point A is above a sidewalk at the entrance to a house. Point B is above the driveway at the same house. Point C is above an alley used by delivery trucks. Which clearance is violated?

Overhead service clearance diagram showing three measurement points: A above sidewalk at 11 feet, B above residential driveway at 12 feet, C above commercial alley at 16 feet

Point A at 11 feet is a violation — pedestrian entrance needs 10 feet minimum (compliant, actually)
Point C at 16 feet is a violation — truck traffic alley needs 18 feet minimum
Point B at 12 feet is a violation — residential driveway needs 15 feet minimum
No violations — all three points meet their clearance requirements

NEC Reference: NEC 230.24(B)

Question 20: When calculating voltage drop for a 3-phase circuit, the formula uses a √3 (approximately 1.732) multiplier that is not used in the single-phase formula. Why?

Three-phase circuits are more efficient, so they need a smaller multiplier
The √3 factor accounts for the geometric relationship between line-to-line voltage and phase voltage in a 3-phase system
The multiplier compensates for the three neutral conductors in the circuit
No multiplier is needed — the formula is the same as single-phase

NEC Reference: NEC Chapter 9, Note 2

Question 21: The minimum headroom of the working space in front of a panelboard, switchboard, or motor control center must be at least:

6 feet
6.5 feet (2.0 m)
7 feet
8 feet

NEC Reference: NEC 110.26(A)(3)

Question 22: Ten 10 AWG THWN conductors (all current-carrying) are run in a conduit in a machine room where the ambient temperature is 45°C. Applying both the temperature correction (0.82 for 45°C at 75°C insulation) and the bundling factor (50% for 10 conductors), what is the adjusted ampacity of each conductor?

14A — 35A × 0.82 × 0.50
18A — 35A × 0.50 (bundling only, ignoring temperature)
22A — 35A × 0.82 (temperature only, ignoring bundling)
29A — 35A × 0.82 (no bundling needed for 10 AWG)

NEC Reference: NEC Tables 310.15(B)(1) and 310.15(C)(1)

Question 23: Per 230.2, how many utility services (service drops or service laterals) are normally permitted for a single building or structure?

No limit — the owner decides how many services to install
One service, unless a listed exception applies
Two services — one for normal, one for emergency
Three services — one per phase of the electrical system

NEC Reference: NEC 230.2

Question 24: The electrical room diagram shows a 480V switchboard against a wall. There is 2.5 feet of clear space between the front of the switchboard and a column directly in front of it. The switchboard has exposed live parts on the front only (Condition 1). Is this working clearance adequate?

Electrical room floor plan showing 480V switchboard with 2.5 feet clearance to a structural column directly in front

Yes — 2.5 feet is enough for a 480V switchboard
No — 480V Condition 1 requires at least 3 feet of working clearance
Yes — the 3-foot rule only applies when the switchboard is open
No — 480V equipment always requires at least 4 feet regardless of condition

NEC Reference: NEC Table 110.26(A)(1)

Question 25: Branch circuit conductors feeding equipment with 60°C rated terminations must be sized using which column from Table 310.16, regardless of the conductor insulation temperature rating?

The 90°C column — THHN wire is 90°C rated
The 75°C column — THWN is more commonly used
The 60°C column — the terminal rating limits you to 60°C ampacity
Either the 60°C or 75°C column, whichever gives a smaller wire

NEC Reference: NEC 110.14(C)(1)(a)

Question 26: A mechanical contractor wants to run a water supply pipe through the dedicated electrical space directly above a 200A panelboard. Is this permitted?

Yes — water pipe above the panel is fine as long as it does not drip
No — foreign systems including pipes are not permitted in the dedicated electrical space
Yes — but a drip shield must be installed above the panel
Yes — the pipe is permitted if it runs parallel to the panel, not over it

NEC Reference: NEC 110.26(F)(1)(b)

Key NEC References for This Test

Article	What It Covers
Art. 220	Load Calculations — optional and standard methods for multifamily
Art. 230	Services — service design, sizing, multiple disconnects
Art. 430	Motors — complete branch circuit design (conductor + OCPD + overload + disconnect)
Art. 445	Generators — standby systems, transfer switches
Art. 450	Transformers — sizing, primary/secondary OCPD, installation
Art. 706	Energy Storage Systems — battery/solar storage (major NEC 2026 expansion)

Study Tip: Practice transformer kVA calculations daily. Know the formula: I = kVA × 1000 ÷ (V × 1.732) for three-phase. This comes up on almost every master exam.

Master Electrician Practice Test - Advanced Mixed Topics

How this test works

Frequently Asked Questions

Before You Start

Topics in This Test

Student Reviews

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Key NEC References for This Test

Master Electrician Practice Test - Advanced Mixed Topics

How this test works

Frequently Asked Questions

Is this Master Electrician Practice Test - Advanced Mixed Topics free?

How do I qualify for the Master Electrician exam?

What is covered on the Master Electrician exam?

How is the Master exam different from the Journeyman exam?

Before You Start

Topics in This Test

Student Reviews

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Master Electrician Practice Test - Advanced Mixed Topics — Question List

Question 1: In a 3-phase, 4-wire wye system where more than 50% of the load is nonlinear (computers, VFDs, LED drivers), how is the neutral treated when counting current-carrying conductors for derating?

Question 2: The NEC defines a continuous load as a load that is expected to continue without interruption for at least:

Question 3: A 6 AWG THWN copper conductor (75°C rated, 65A per Table 310.16) is installed in a location where the ambient temperature is 50°C. What is the corrected ampacity?

Question 4: Eight 10 AWG THWN conductors (35A ampacity each) are all installed in the same conduit, and all eight are current-carrying. What is the adjusted ampacity for each conductor?

Question 5: The NEC has an informational note that recommends keeping voltage drop at or below what percentage for branch circuits, and what combined percentage for the whole system (feeder + branch)?

Question 6: When two or more conductors are installed in parallel to form a single large feeder, each individual conductor must be at least what size?

Question 7: Service drop conductors passing over a residential driveway must maintain a minimum clearance above the ground of:

Question 8: Service drop conductors passing over a public street or road subject to truck traffic must maintain a minimum ground clearance of:

Question 9: How many service disconnects are allowed per service, per 230.71?

Question 10: The dedicated electrical space above a panelboard must extend how far above the top of the equipment?

Question 11: A 480V switchboard has exposed live parts on one side of the working space and grounded metal parts on the other (Condition 2). What is the minimum working clearance depth in front of the switchboard?

Question 12: In a 120/240V, 4-wire delta service (high-leg delta), one phase has a higher voltage to ground than the other two. This phase must be identified with what color, and which phase position is it in?

Question 13: You install 1/0 AWG THHN conductors (90°C insulation, 170A per Table 310.16). The terminations on the panel and equipment are marked "75°C." Which ampacity column from Table 310.16 must you use?

Question 14: Five 12 AWG THWN conductors (all current-carrying) are in the same conduit. What bundling adjustment factor applies, and what is the adjusted ampacity of each conductor?

Question 15: An electrician installs a motor according to all NEC rules, but the motor manufacturer instructions say to use a specific wiring method and conductor size that is more restrictive than what the NEC requires. Which takes precedence?

Question 16: Service drop conductors at the point where they enter a dwelling (over a porch or walkway accessible only to pedestrians) must be at least how many feet above the ground?

Question 17: During construction, temporary feeder cables that run on the ground across a work site must be:

Question 18: Electrical equipment installed in a chemical storage room where the atmosphere could corrode metal parts must be:

Question 19: The overhead clearance diagram shows a service drop crossing over different areas. Point A is above a sidewalk at the entrance to a house. Point B is above the driveway at the same house. Point C is above an alley used by delivery trucks. Which clearance is violated?

Question 20: When calculating voltage drop for a 3-phase circuit, the formula uses a √3 (approximately 1.732) multiplier that is not used in the single-phase formula. Why?

Question 21: The minimum headroom of the working space in front of a panelboard, switchboard, or motor control center must be at least:

Question 23: Per 230.2, how many utility services (service drops or service laterals) are normally permitted for a single building or structure?

Question 24: The electrical room diagram shows a 480V switchboard against a wall. There is 2.5 feet of clear space between the front of the switchboard and a column directly in front of it. The switchboard has exposed live parts on the front only (Condition 1). Is this working clearance adequate?

Question 25: Branch circuit conductors feeding equipment with 60°C rated terminations must be sized using which column from Table 310.16, regardless of the conductor insulation temperature rating?

Question 26: A mechanical contractor wants to run a water supply pipe through the dedicated electrical space directly above a 200A panelboard. Is this permitted?

Key NEC References for This Test

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