Domain-by-Domain Content Review: NCCER Levels 1–4 and OSHA 10

Why Domain-by-Domain Review Works

Preparing for multiple credentials at once—NCCER Electrical Levels 1–4, OSHA 10, and the State Journeyman Electrician license—can feel overwhelming. The most reliable strategy is to attack one knowledge domain at a time, confirm your retention with a scored quiz, and fix gaps before moving on. This lesson maps every major domain you will be tested on, explains what to focus on in each, and describes how the quiz-and-remediation cycle keeps you on track.

NCCER Electrical Domain Group 1: DC/AC Theory Fundamentals

Electrical theory is the foundation everything else builds on. For DC circuits, you must be comfortable with Ohm's Law (V = IR), power relationships (P = IE, P = I²R, P = V²/R), and series-parallel circuit behavior. For AC circuits, focus on how voltage and current relate in purely resistive, inductive, and capacitive circuits; how to calculate impedance; and what power factor means in a practical sense. Know the difference between RMS and peak voltage values. NCCER Level 1 and Level 2 both draw heavily on these ideas, and licensing exams often embed theory into calculation scenarios.

NCCER Domain Group 2: Wiring Methods, Raceways, and Conductors

This domain covers the physical installation of electrical systems. You need to know conductor ampacity from NEC Chapter 3 tables, how to apply correction factors for temperature and conduit fill, conduit types (EMT, IMC, rigid metal, PVC, and flexible), and box-fill calculations under NEC Article 314. Wiring methods differ by occupancy and location—outdoor, wet, hazardous, or concealed—so be ready to select the correct method for a given scenario. NCCER Levels 2 and 3 contain the bulk of this material.

NCCER Domain Group 3: NEC Load Calculations and Overcurrent Protection

Load calculations determine the minimum service size, feeder ampacity, and branch-circuit requirements for residential and commercial occupancies. NEC Article 220 is your primary reference. You will calculate general lighting loads using unit load values, add appliance and motor loads, apply demand factors where permitted, and size overcurrent protective devices (OCPDs) accordingly. Know the difference between fuses and circuit breakers, interrupting ratings, and when GFCI or AFCI protection is required by the NEC. This domain appears on both NCCER assessments and most journeyman licensing exams.

NCCER Domain Group 4: Grounding and Bonding

NEC Article 250 governs grounding and bonding. Grounding provides a reference to earth; bonding creates an effective fault-current path to operate the OCPD. Know the difference between the grounding electrode conductor, equipment grounding conductor, and main bonding jumper. Understand why a low-impedance fault path—not earth resistance alone—is what clears a fault safely and quickly. Journeyman exams frequently test Article 250 because errors here cause electrocution and equipment damage.

NCCER Domain Group 5: Motors, Motor Controls, and PLCs

NCCER Level 3 covers motors in depth. For the exam: nameplate data (voltage, full-load amperes, service factor, efficiency class), motor branch-circuit protection sizing per NEC Article 430, starter types (across-the-line, reduced-voltage, variable-frequency drives), and control ladder logic basics. Programmable Logic Controllers (PLCs) appear in Level 4; you should understand input/output modules, basic ladder-logic rungs, and safe energy isolation before working on any controlled system.

NCCER Domain Group 6: Residential and Commercial Service Installation

Level 3 and Level 4 move from individual circuits to complete services. For residential work, know service-entrance conductor sizing, meter base installation, main panel layout, and the rules for separate buildings. For commercial work, understand switchgear, panelboards, feeders, transformer sizing basics, and the difference between single-phase and three-phase distribution. Code-book speed drills in this course simulate the time pressure of the licensing exam; practice turning to the right article and table quickly.

OSHA 10 Required Topic Areas

OSHA 10 is not an electrical exam—it is a safety awareness credential. The required topic areas include:

• Fall protection – guardrail systems, personal fall arrest systems, ladder safety (NEC and OSHA ladder rules overlap; know both).
• Electrical hazards and NFPA 70E awareness – shock, arc-flash, and arc-blast; approach boundaries; the role of an energized electrical work permit.
• Struck-by and caught-in hazards – tool and material handling, overhead work zones, rotating equipment.
• PPE selection – matching the hazard to the correct PPE class; insulated gloves and tools for electrical work; hard hats, safety glasses, and flame-resistant clothing where required.
• Hazard Communication (HazCom) – the GHS-aligned Safety Data Sheet (SDS) format and its sixteen sections; label elements including pictograms and signal words.
• Lockout/Tagout (LOTO) – the single most critical safety procedure for electricians; OSHA 29 CFR 1910.147 covers the general industry standard and 29 CFR 1926.417 covers construction; know the sequence: identify, isolate, lock, try, work, remove in proper order.

Safety reminder: Never assume a circuit is de-energized. Always verify with a properly rated test instrument after applying LOTO, and treat every conductor as live until proven otherwise.

The 75 Percent Threshold and Remediation Cycle

After each domain session you will take a 25-question timed quiz. A score below 75 percent (fewer than 19 correct) means that domain needs more work before you are ready for a licensing exam. You will complete a 30-minute peer-study or instructor-led re-teach, then take an alternate 25-question quiz. Both scores are logged. This process protects you: licensing exams and real job sites do not allow partial credit for dangerous knowledge gaps.