What score do I need to pass a master electrician exam?

Most jurisdictions set the master cut score between 70% and 75%, the same band as the journeyman exam. This practice test grades against 70%, but check your state or local licensing board for the exact passing score and the NEC edition your exam references.

How is the master electrician exam different from the journeyman exam?

The master exam leans harder on load and design calculations: motor branch-circuit and feeder sizing (Article 430), transformer overcurrent (450.3(B)), service and feeder load calculations (Article 220, including the optional methods), and grounding and bonding conductor sizing. It also tests business and code-administration topics on many state exams. This set focuses on the NEC calculation and rule questions.

Is the master electrician exam open-book?

Most master exams are open-book with the NEC as the permitted reference, and speed of navigation is decisive on the multi-step calculation questions. Practice finding Tables 430.250, 430.52, 450.3(B), 250.66, 250.122, and 220.55 quickly. The calculation questions in this set are built directly on those tables.

Master Electrician Practice Test

Twenty master-level questions on the National Electrical Code (NEC), weighted toward motor and feeder calculations, transformer sizing, and grounding. Graded instantly with the arithmetic worked out and the governing table or article cited on every answer.

Question 1 of 20 · Motor calculations

A 50 hp, 460 V, three-phase squirrel-cage motor is being sized for conductors and overcurrent protection. The full-load current used for those calculations, per NEC 430.6(A)(1), is:

52 A 65 A 77 A 96 A

Question 2 of 20 · Motor calculations

For that same 50 hp, 460 V motor (full-load current 65 A), the maximum inverse-time circuit breaker for branch-circuit short-circuit and ground-fault protection is:

150 A 162.5 A 175 A 200 A

Question 3 of 20 · Motor calculations

A single 30 hp, 460 V, three-phase motor (full-load current 40 A) runs continuously. The minimum branch-circuit conductor ampacity required by NEC 430.22 is:

40 A 46 A 50 A 57.5 A

Question 4 of 20 · Motor calculations

A continuous-duty motor has a nameplate full-load current of 28 A and a marked service factor of 1.15. The maximum separate running-overload device, before any 430.32(C) increase, is:

28 A 32.2 A 35 A 39.2 A

Question 5 of 20 · Motor calculations

A feeder supplies two three-phase, 460 V motors: one 50 hp (full-load current 65 A) and one 30 hp (full-load current 40 A). The minimum feeder conductor ampacity per NEC 430.24 is:

105 A 121.25 A 131.25 A 146.25 A

Question 6 of 20 · Motor calculations

For that same two-motor feeder (50 hp branch device 175 A, 30 hp full-load current 40 A), the maximum feeder short-circuit and ground-fault protective device (inverse-time breaker) per NEC 430.62 is:

175 A 200 A 215 A 225 A

Question 7 of 20 · Transformer sizing

A 45 kVA, three-phase transformer has a 480 V primary and is protected by a primary-only overcurrent device (no individual secondary protection). The maximum primary circuit breaker per NEC Table 450.3(B) is:

60 A 70 A 90 A 110 A

Question 8 of 20 · Service and feeder load

A single 16 kW household electric range is served by an individual branch circuit. Its demand load, using NEC Table 220.55 Column C with Note 1, is:

8 kW 9.6 kW 14 kW 16 kW

Question 9 of 20 · Voltage drop

A 460 V, three-phase feeder carries 150 A over a 200 ft one-way run in 3/0 AWG copper (Chapter 9 Table 9 AC resistance, 0.077 ohm per 1000 ft). The approximate voltage drop is:

2.3 V 4.0 V 4.6 V 6.9 V

Question 10 of 20 · Grounding and bonding

A 400 A overcurrent device protects a feeder. The minimum copper equipment grounding conductor per NEC Table 250.122 is:

4 AWG 3 AWG 2 AWG 1 AWG

Question 11 of 20 · Grounding and bonding

A service is supplied by 350 kcmil copper service-entrance conductors. The minimum copper grounding electrode conductor per NEC Table 250.66 is:

4 AWG 3 AWG 2 AWG 1/0 AWG

Question 12 of 20 · Box fill

A junction box contains six 6 AWG conductors and no devices, clamps, or grounding conductors. The minimum box volume from the conductor fill alone, per NEC Table 314.16(B), is:

13.5 in³ 15 in³ 27 in³ 30 in³

Question 13 of 20 · Service and feeder load

Under the optional calculation for a dwelling (NEC 220.82), after summing the general loads, the demand applied is 100% of the first 10 kVA and ______ of the remainder.

25% 35% 40% 50%

Question 14 of 20 · Service and feeder load

Using the standard calculation, the general lighting and receptacle load for a dwelling is subject to demand factors: 100% of the first 3000 VA and ______ of the portion from 3001 VA to 120,000 VA.

25% 35% 40% 50%

Question 15 of 20 · Transformer sizing

Conductors supplied by a transformer secondary, with no overcurrent device at the secondary terminals, are protected under the tap rules of NEC 240.21(C), which include the ______ tap allowances.

10 ft and 25 ft 6 ft and 10 ft 25 ft and 100 ft 3 ft and 10 ft

Question 16 of 20 · Motor calculations

The disconnecting means for a single motor rated more than 2 hp must have an ampere rating of at least ______ of the motor full-load current.

100% 115% 125% 150%

Question 17 of 20 · Grounding and bonding

For service raceways, the supply-side bonding jumper (line side of the service) is sized from the same table used to size the:

Equipment grounding conductor (Table 250.122) Grounding electrode conductor (Table 250.66) Branch-circuit conductor (Table 310.16) Feeder tap conductor (240.21)

Question 18 of 20 · Motor calculations

Per NEC Table 430.52, the maximum rating of an inverse-time circuit breaker for a squirrel-cage motor (other than Design B energy-efficient), as a percent of full-load current, is:

150% 175% 250% 300%

Question 19 of 20 · Service and feeder load

When sizing a feeder or service neutral, NEC 220.61 permits a demand factor of ______ on that portion of the unbalanced (neutral) load that exceeds 200 A.

50% 70% 80% 100%

Question 20 of 20 · Service and feeder load

Before any ampacity adjustment or correction, a feeder supplying continuous and noncontinuous load must have conductors sized for 100% of the noncontinuous load plus ______ of the continuous load.

100% 115% 125% 150%

How to use this practice test

Work through all 20 questions. Treat it as closed-book on the rule questions and open-book on the calculations, the way exam time pressure actually plays out.
Grade the test. Each question reveals the worked answer and its NEC reference.
For any miss, look up the cited table or article and re-derive the answer yourself. On the master exam the multi-step motor and feeder problems reward fast, confident navigation.
Use the site's calculators (linked below) to check your own re-derivations.

NEC reference

Questions reference the NEC 2020 edition. Answers use values that are identical in the 2017, 2020, and 2023 editions unless the explanation says otherwise. Motor full-load currents (Tables 430.248/430.250), the Table 430.52 percentages, Table 450.3(B), Table 250.66, and Table 250.122 are unchanged across those editions. Section numbering follows the 2020/2023 editions; in NEC 2017, Table 310.16 was 310.15(B)(16) and Table 310.15(C)(1) was 310.15(B)(3)(a). The general-lighting demand factors in Table 220.42 were relocated to Table 220.45 in NEC 2023 with the same percentages. Every calculated answer in this set is verified against the same National Electrical Code table data that powers this site's calculators. Tables 430.248, 430.250, 430.52, 450.3(B), 220.55, 310.16, 314.16(B), 250.66, 250.122, and Chapter 9 Tables 8 and 9.

Results are for reference only. Verify against the applicable adopted edition of the NEC and consult a licensed electrician for code compliance.

Continuing education and exam prep

Many licensing jurisdictions require continuing education hours each renewal cycle. Mike Holt's continuing education courses are organized by state, and his exam preparation programs cover journeyman and master license exams. Confirm any course is approved for your license and jurisdiction before enrolling.

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Check your work with the calculators

Newer to the exam? The journeyman practice test covers the same tables at a lighter weight. Working in a specific state? Confirm which NEC edition your state enforces. Your exam references the adopted edition.

Below the cut score on this set

How to use this practice test

NEC reference

Continuing education and exam prep

Check your work with the calculators