Journeyman/Master Electrician License Exam Low-Voltage, Communications, and Code Application Flashcards

24 sample cards from the Low-Voltage, Communications, and Code Application deck

Sampled from the end of the deck, so these are different cards from the ones shown on the syllabus page.

1. What is the conductor voltage-drop formula commonly used on the exam (single-phase)?

   $V_{D} = \frac{2 \times K \times I \times L}{CM}$, where $K$ is the conductor constant (about 12.9 for copper, 21.2 for aluminum), $I$ is current, $L$ is one-way length in feet, and $CM$ is the conductor area in circular mils.

2. What constant $K$ values are used for copper and aluminum in voltage-drop calculations?

   $K \approx 12.9$ ohm-circular-mils per foot for copper and $K \approx 21.2$ for aluminum (at typical operating temperatures).

3. What is the formula for the three-phase voltage drop on a feeder?

   $V_{D} = \frac{\sqrt{3} \times K \times I \times L}{CM}$, where $L$ is the one-way length; note the multiplier is $\sqrt{3}$ for three-phase versus $2$ for single-phase.

4. What is the maximum recommended voltage drop per the NEC for branch circuits and for the combined feeder plus branch circuit?

   The NEC recommends (informational, not mandatory) a maximum of 3% voltage drop on a branch circuit or feeder, and not more than 5% total for the combined feeder and branch circuit.

5. How do you convert between horsepower and watts for motor calculations?

   $1 \text{ hp} = 746 \text{ W}$. So output power in watts $= hp \times 746$ (divide by efficiency to get input watts).

6. How do you convert kilowatts to BTU per hour, a common HVAC/load conversion?

   $1 \text{ kW} = 3412 \text{ BTU/hr}$ (approximately). Multiply kW by 3412 to obtain BTU/hr.

7. What is the general area derating relationship between AWG sizes (the rule of thumb for circular mils)?

   For every decrease of 3 AWG sizes the circular-mil area roughly doubles, and for every decrease of 10 AWG sizes the area increases about tenfold. Smaller AWG number = larger conductor.

8. How do you convert circular mils to square inches, and what is a circular mil?

   A circular mil is the area of a circle 1 mil (0.001 in) in diameter: $A_{CM} = d_{mils}^{2}$ where $d$ is in mils. To convert, $1 \text{ in}^{2} \approx 1{,}273{,}240$ circular mils.

9. What is OSHA, and what is its relationship to electrical safety on the job?

   OSHA (Occupational Safety and Health Administration) is the federal agency that sets and enforces workplace safety regulations (29 CFR 1910 for general industry, 1926 for construction). It adopts consensus standards like NFPA 70E for electrical safe work practices.

10. What is NFPA 70E and how does it differ from the NEC (NFPA 70)?

    NFPA 70E is the Standard for Electrical Safety in the Workplace, covering safe work practices, arc-flash hazards, PPE, and the energized-work permit. The NEC (NFPA 70) covers safe installation of wiring and equipment. 70E protects workers; the NEC governs installations.

11. Under NFPA 70E, what is the 'electrically safe work condition' and the basic process to establish it (lockout/tagout)?

    It is the state where equipment is de-energized and verified safe. The steps: identify all sources, interrupt the load and open disconnects, visually verify isolation, apply lockout/tagout, test for absence of voltage with a tester (and verify the tester before and after), and ground if needed.

12. In NFPA 70E, what is an arc-flash boundary?

    The arc-flash boundary is the distance from a potential arc source at which the incident energy equals $1.2 \text{ cal/cm}^{2}$ (the onset of a second-degree burn on bare skin). Inside this boundary, arc-rated PPE is required.

13. What does NFPA 70E require before performing energized work that cannot be avoided?

    An energized electrical work permit, justification that de-energizing is infeasible or creates greater hazard, a job safety/risk assessment, appropriate arc-rated PPE per the incident-energy analysis or PPE category tables, and qualified-person status.

14. What is an AHJ in the context of electrical permits and inspections?

    The Authority Having Jurisdiction: the office, individual, or body (often the local electrical inspector or building department) responsible for approving equipment, materials, installations, and procedures and for enforcing the adopted code. The AHJ has final interpretation authority locally.

15. Why is an electrical permit typically required before starting work, and who usually pulls it?

    A permit ensures the work is reviewed and inspected for code compliance and safety. The licensed electrical contractor (or, in some jurisdictions, the homeowner for their own residence) pulls the permit before work begins; doing work without a required permit can void approvals and incur penalties.

16. What is the typical sequence of electrical inspections on a new construction project?

    Generally: (1) underground/trench inspection before backfill, (2) rough-in inspection after wiring is run but before walls are closed, and (3) final inspection after devices, fixtures, and the service are complete and energized-ready. Each must pass before proceeding.

17. What does it mean when the NEC says equipment must be 'listed' or 'labeled,' and who relates this to the AHJ?

    'Listed' means a qualified testing lab (NRTL such as UL) has evaluated the product and it appears on a published list; 'labeled' means it bears that lab's mark. The AHJ relies on listing/labeling as evidence of suitability and may require it for approval.

18. What is the difference between a journeyman and a master electrician license?

    A journeyman is licensed to perform electrical installation work, typically under the responsibility of a master, after completing an apprenticeship and required hours. A master electrician has additional experience and exam requirements, can pull permits, supervise journeymen/apprentices, and often own/operate a contracting business.

19. Who establishes electrician licensing requirements in the United States, and why do they vary?

    Licensing is governed at the state and often local (city/county) level, not federally, so requirements (experience hours, exam content, reciprocity, continuing education) vary by jurisdiction. Always verify with the specific state licensing board.

20. What is reciprocity in electrical licensing?

    Reciprocity is an agreement between states (or jurisdictions) to recognize each other's electrician licenses, allowing a licensed electrician to obtain a license in another participating state without retaking all exams, provided requirements are comparable.

21. What are typical experience-hour requirements before sitting for a journeyman vs. master electrician exam?

    A journeyman typically requires about 8,000 hours (roughly 4 years) of supervised on-the-job experience plus schooling; a master typically requires an additional ~2,000+ hours (often 2 years as a licensed journeyman) before qualifying for the master exam. Exact hours vary by state.

22. On the licensing exam, how is the adopted NEC edition determined for a given jurisdiction?

    Each state or local AHJ adopts a specific edition/cycle of the NEC (which updates every 3 years), sometimes with amendments. The exam is based on the edition currently adopted by that jurisdiction, so candidates must study the correct adopted edition.

23. What is the bonding conductor minimum size for grounding a communications or coax primary protector, and why does size matter?

    Not smaller than 14 AWG copper. The bonding/grounding conductor must safely carry surge and fault currents to the grounding electrode; an adequately sized, short conductor keeps impedance low so dangerous voltages are quickly diverted to ground.

24. What is the key separation rule for Class 2/Class 3 (Article 725) and communications (Article 800) cables relative to electric light and power conductors?

    Power-limited and communications conductors must be separated from electric light, power, Class 1, and NPLFA conductors by at least 2 inches unless the power conductors are in a raceway or metal-sheathed/UF cable, or a permanent barrier separates them. This prevents energy from the higher-power circuit reaching the low-voltage wiring.

What this deck covers

Low-Voltage, Communications, and Code Application flashcards FAQ