CSLB General Building (B) Trade Practice Test
Frequently asked questions
How many Master Electrician (NEC) practice questions are here?+
A full bank of original Master Electrician (NEC) practice questions across the official content areas, weighted like the real exam, with explanations. Free, no signup.
What is the Master Electrician (NEC) exam like?+
About 100 questions, 300 minutes, and you need 75% to pass. Practice by topic here, then take the full timed mock exam to gauge readiness.
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PrepPass practice is in English, 中文 and Español. The official exam is in English — switch the question language to English any time to rehearse the exact terminology you'll see on test day.
Sample practice questions
A few real questions from this free bank, with full explanations. Use the practice tool above for the whole set.
- 1. Calculations
A single-family dwelling has 2,000 sq ft of habitable floor area. Using the standard calculation method at 3 VA per sq ft, what is the general lighting and general-use receptacle load before any demand factors?
- a.6,000 VA
- b.4,000 VA
- c.8,000 VA
- d.3,000 VA
Answer: a
Explanation: General lighting is figured at 3 VA per sq ft: 2,000 sq ft x 3 VA = 6,000 VA. This value is calculated before applying the general-lighting demand factors.
- 2. Calculations
An electric range has a Column C demand of 8,000 VA. Using the 70% neutral demand for ranges, what is the range contribution to the feeder neutral load?
- a.8,000 VA
- b.4,000 VA
- c.7,000 VA
- d.5,600 VA
Answer: d
Explanation: The feeder neutral for a household range may be figured at 70% of the range demand: 8,000 x 0.70 = 5,600 VA.
- 3. Calculations
A 208-V three-phase feeder carries 40 A over 150 ft using #6 Cu (CM = 26,240, K = 12.9). What is the approximate voltage drop?
- a.3.0 V
- b.7.2 V
- c.5.1 V
- d.9.0 V
Answer: c
Explanation: Three-phase VD = (1.732 x K x I x L) / CM = (1.732 x 12.9 x 40 x 150) / 26,240 = 134,050 / 26,240 = 5.11 V.
- 4. Services & Distribution
A branch circuit is protected by a 100-A overcurrent device. What is the minimum copper equipment grounding conductor?
- a.#10 AWG
- b.#8 AWG
- c.#6 AWG
- d.#4 AWG
Answer: b
Explanation: The equipment grounding conductor table requires #8 Cu for an overcurrent device rating up to 100 A.
Source: 2023 NEC Table 250.122
- 5. Services & Distribution
What is the minimum service disconnecting-means rating for a one-family dwelling?
- a.100 A
- b.60 A
- c.125 A
- d.200 A
Answer: a
Explanation: The service disconnecting means for a one-family dwelling must be rated at least 100 A, 3-wire.
Source: 2023 NEC 230.79
- 6. Advanced Wiring
A location where ignitable concentrations of flammable gases or vapors exist under normal operating conditions is classified as:
- a.Class II, Division 1
- b.Class III
- c.Class I, Division 2
- d.Class I, Division 1
Answer: d
Explanation: Class I covers flammable gases/vapors; Division 1 means ignitable concentrations can exist under normal operation, so it is Class I, Division 1.
Source: 2023 NEC 500.5(B)(1)
- 7. Advanced Wiring
Which nameplate value on an air-conditioning unit is used to size the branch-circuit conductors?
- a.Maximum overcurrent protection
- b.Nameplate horsepower
- c.Minimum circuit ampacity
- d.Rated-load amps only
Answer: c
Explanation: Conductors are sized to the marked minimum circuit ampacity (MCA); the maximum overcurrent protective device (MOCP) sizes the breaker or fuse.
Source: 2023 NEC 440.4
- 8. Theory & Design
A load draws 80 kW of real power and 100 kVA of apparent power. What is the power factor?
- a.1.0
- b.0.8
- c.0.6
- d.0.9
Answer: b
Explanation: Power factor = real power / apparent power = 80 kW / 100 kVA = 0.8.
- 9. Theory & Design
A single-line (one-line) diagram represents an electrical system by:
- a.One line for each circuit or set of conductors
- b.Each individual conductor drawn separately
- c.The physical layout of raceways
- d.Only the branch-circuit wiring
Answer: a
Explanation: A one-line diagram uses a single line and standard symbols to represent circuits and equipment, simplifying analysis of the power system.
- 10. Code Admin & Safety
Equipment rated at what current or more requires two entrances to and egress from the working space when the space is large or contains overcurrent devices?
- a.800 A
- b.600 A
- c.1000 A
- d.1200 A
Answer: d
Explanation: For equipment rated 1,200 A or more and over 6 ft wide, two entrances/egress paths to the working space are required.
Source: 2023 NEC 110.26(C)(2)