Mixed Deck — All Journeyman Electrician’s Exam Topics Flashcards
100 cards from real Journeyman Electrician’s Exam practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 20 Mixed Deck — All Journeyman Electrician’s Exam Topics flashcards as text
Per NEC 408.36(D), a back-fed circuit breaker used as the supply overcurrent protective device for a panelboard must be:
Answer: Secured in place by an additional fastener that requires other than a pull to release
NEC 408.36(D) requires back-fed devices to be secured with an additional fastener that requires more than a simple pull to release, preventing accidental removal under load.
A feeder supplies a continuous load of 80A. What is the minimum conductor ampacity required before applying breaker sizing?
Answer: 100A
Conductors for continuous loads must be sized at 125% of the load (80A × 1.25 = 100A) per NEC 215.2.
Which motor protection scheme uses a set of normally-closed auxiliary contacts from one contactor wired in series with the coil of the other contactor to prevent both from energizing simultaneously?
Answer: Electrical interlocking
Electrical interlocking uses NC auxiliary contacts from each contactor in the opposing contactor's coil circuit to prevent simultaneous energization (common in reversing starters).
If the computation for branch-circuits yields a value of 3.1, how many branch-circuits should be installed?
Answer: 4
When calculating the number of branch circuits required, any fractional result must always be rounded up to the next whole number. This ensures that there is sufficient capacity to safely handle the calculated load, preventing overloading and ensuring compliance with electrical codes. Therefore, 3.1 branch circuits would necessitate installing 4 circuits.
When emergency system wiring must occupy the same enclosure as normal wiring at a transfer switch, this is permitted because:
Answer: NEC 700.10(B)(5) specifically exempts transfer equipment from the independence requirement
NEC 700.10(B)(5) provides a specific exception to the wiring independence rule at transfer equipment, since this is the inherent connection point between the two sources.
Rigid PVC Conduit (Schedule 40 and Schedule 80) is governed by which NEC article?
Answer: Article 352
NEC Article 352 covers Rigid PVC Conduit, including both Schedule 40 and Schedule 80, and specifies where each schedule is permitted.
A commercial building has 50 kVA of fluorescent lighting. Using standard demand factors, what minimum amperage feeder is required on a 208Y/120V, 3-phase system?
Answer: 139 A
50,000 VA ÷ (208V × 1.732) = 138.8 A, so a 139 A minimum feeder is required.
In a 3-phase, 4-wire wye system where the line-to-line voltage is 208V, what is the line-to-neutral (phase) voltage?
Answer: 120 volts
Phase voltage = line voltage ÷ √3 = 208 ÷ 1.732 ≈ 120V, the standard single-phase voltage in a 208Y/120V system.
For load calculation purposes, each 2-foot (600 mm) section of lighting track shall be considered a load of:
Answer: 150 volt-amperes
NEC 410.151(B) specifies that each 2-foot section of lighting track or fraction thereof shall be considered a load of 150 volt-amperes when calculating circuit load.
What is the inductive reactance (XL) of a 0.2 Henry inductor at 60 Hz?
Answer: 75.4 ohms
XL = 2πfL = 2 × 3.14159 × 60 × 0.2 = 75.4 ohms.
When installing multiple circuits in the same raceway, what determines the minimum size of a single equipment grounding conductor (EGC) for all circuits?
Answer: The ampere rating of the largest overcurrent device in the raceway.
According to NEC 250.122(C), when a single equipment grounding conductor is installed for multiple circuits in the same raceway, its size must be based on the rating of the largest overcurrent protective device protecting any of the circuits in that raceway.
Which of the following is the correct formula to calculate the resistance of a conductor?
Answer: R = V / I
Ohm's Law states that resistance equals voltage divided by current (R = V/I), the fundamental relationship in electrical circuits.
What is the minimum size copper equipment grounding conductor (EGC) required for a circuit protected by a 60-amp overcurrent device?
Answer: 10 AWG
NEC Table 250.122 requires a minimum 10 AWG copper EGC for circuits protected by overcurrent devices rated up to 60 amps.
According to NEC 210.52(E), what receptacle outlet placement is required for hallways in dwelling units that are 10 feet or more in length?
Answer: At least one receptacle outlet
NEC 210.52(H) requires at least one receptacle outlet in hallways of dwelling units that are 10 feet or more in length.
What is the primary purpose of a buck-boost transformer?
Answer: Make small line voltage corrections of approximately 5–20%
Buck-boost transformers are used to raise (boost) or lower (buck) line voltage by small amounts—typically 5–20%—to correct for voltage drop or overvoltage.
A 10 HP, 230V, single-phase motor has a full-load current of 50A per NEC Table 430.248. What minimum ampacity must the branch-circuit conductors have?
Answer: 62.5A
Branch-circuit conductors must be sized at 125% of FLC: 50A × 1.25 = 62.5A minimum ampacity per NEC 430.22.
Per NEC 250.122, if a 200-ampere circuit breaker protects a feeder, what is the minimum size equipment grounding conductor required for copper conductors?
Answer: #4 AWG copper
Per NEC Table 250.122, a 200-ampere overcurrent device requires a minimum #4 AWG copper equipment grounding conductor.
What is a transformer's maximum short-circuit fault current when the secondary nameplate rating is 75 kva, 120/240 volts, single-phase, and 2.5% Z?
Answer: 312.5 (transformer full-load amperes) x 40 (multiplier) = 12,500 short-circuit fault current
The full-load secondary current is 75,000 ÷ 240 = 312.5 amperes, and the multiplier is 100 ÷ 2.5% = 40, so 312.5 × 40 = 12,500 amperes of short-circuit fault current. The other options each show only one intermediate step, while the correct answer combines them into the final result.
A commercial space has 50 duplex receptacle outlets. Per NEC 220.14(I), what is the total calculated receptacle load?
Answer: 9,000 VA
Per NEC 220.14(I), each duplex receptacle counts as one outlet at 180 VA, so 50 × 180 VA = 9,000 VA.
In a Class III hazardous location, what is the primary hazard?
Answer: Easily ignitable fibers or flyings
Class III locations are those that are hazardous due to the presence of easily ignitable fibers or flyings, such as cotton, rayon, or hemp.