EEA Electrician Exam cheat sheet

Ohm's law: E = I × R; power P = E × I = I²R = E²/R. In AC circuits use impedance Z and account for phase angle.

Single-phase power: P = E × I × PF. Balanced three-phase: P = √3 × E_line × I_line × PF; apparent power S in VA, reactive power Q in VAR.

Series circuit: current is common, resistances add (R_T = R1 + R2 + …), voltage divides proportionally. Parallel: voltage common, conductances add (1/R_T = 1/R1 + 1/R2 + …).

Conductor resistance: R = ρL/A with ρ in circular-mil-ohms per foot; R rises with temperature and with length, falls with cross-sectional area.

RMS values: for a sine wave, RMS = peak × 0.707 and average = peak × 0.637; RMS is the heating-equivalent value used for power calculations.

Frequency and reactance: X_L = 2πfL, X_C = 1/(2πfC), Z = √(R² + (X_L − X_C)²); resonance occurs when X_L = X_C.

Power factor = kW/kVA = cos θ; low PF increases current for the same real power, raising conductor and voltage-drop losses.

Transformer turns ratio: E_primary/E_secondary = N_primary/N_secondary; current ratio is inverse, and VA is essentially conserved (minus losses).

Voltage drop (single phase) ≈ 2 × K × I × L / CM, where K ≈ 12.9 for copper and ≈ 21.2 for aluminum; CM is circular mils of the conductor.

Conductor ampacity tables are applied with correction factors for ambient temperature and adjustment factors for more than three current-carrying conductors in a raceway or cable.

NM cable (Romex) is limited to dry locations and generally prohibited in wet locations, in raceways outdoors, in hazardous locations, and where subject to physical damage.

RMC, IMC, and EMT differ in wall thickness and permitted use; EMT is permitted in concrete and direct sunlight with listed fittings but not where severe corrosion or physical damage requires rigid.

Raceway fill: conductors must not exceed the permitted percentage of interior cross-sectional area - one conductor 53%, two 31%, over two 40%.

Box fill is calculated from conductor volume allowances plus clamps, support fittings, devices, and equipment grounding conductors; each conductor size has a table volume.

Cable and raceway support intervals and securing distances are method-specific; ENT, PVC, and EMT each have their own maximum support spacing and securement rules.

Bending radius must not be less than the minimum multiple of the raceway or cable diameter specified for the method; kinks and crushed conduit are violations.

Expansion fittings are required where raceways cross building expansion joints and for long straight PVC runs subject to thermal movement.

Liquidtight flexible metal conduit is permitted in wet locations with listed fittings; LFMC in lengths over 1.8 m (6 ft) requires an equipment grounding conductor.

Standard branch-circuit ratings include 15, 20, 30, 40, and 50 A; the overcurrent device rating generally sets the branch-circuit rating.

Receptacle outlets on 15 A and 20 A branch circuits: general-use receptacles must match the circuit rating; a 20 A circuit may use 15 A or 20 A receptacles but a single receptacle must match.

Small-appliance and laundry branch circuits are 20 A and must not serve other outlets; kitchen countertop receptacles require GFCI protection.

Continuous loads are calculated at 125% for branch-circuit and feeder sizing; the overcurrent device must be at least 125% of continuous load plus 100% of noncontinuous load.

General lighting load is based on volt-amperes per square meter (or per square foot) by occupancy type, then demand factors may be applied for dwellings.

Standard service calculation method: general lighting + small appliance + laundry + other loads, apply demand factors, add largest motor at 125%, then size service conductors and equipment.

Feeder and service conductor sizing uses the larger of the calculated load or the existing load, with ampacity adjusted for ambient temperature and conductor count.

Demand factors reduce calculated load for ranges, dryers, and multiple dwelling units; optional calculation methods may produce a smaller service when conditions are met.

Voltage drop on branch circuits and feeders is a design consideration; recommended total drop is about 3% on a branch circuit and 5% overall.

System grounding connects the grounded circuit conductor to earth at the service; equipment grounding bonds non-current-carrying metal parts to provide a low-impedance fault path.

The service neutral (grounded conductor) is bonded to the enclosure and grounding electrode system at the service disconnect only; downstream panels must have separate neutral and ground bars.

Grounding electrode system items include metal underground water pipe, metal frame of the building, concrete-encased electrode, ground ring, rod/pipe electrodes, and plate electrodes.

The grounding electrode conductor is sized from the largest service conductor using the applicable table; the bonding jumper to a water pipe is sized per the same rules.

Equipment grounding conductor sizing is based on the rating of the overcurrent device protecting the circuit, not on the phase conductor ampacity alone.

Bonding jumpers are required around water meters, at metallic gas piping, and across removable or insulating sections of metallic raceways and fittings.

A grounding electrode conductor to a made electrode (rod, pipe, plate) is not required to be larger than 6 AWG copper; rod electrodes must be driven to at least 2.4 m (8 ft) unless rock is encountered.

GFCI protection and equipment grounding are distinct: GFCI protects people from line-to-ground shock, while the EGC provides the fault-return path for overcurrent clearing.

Bonding of service equipment, metal raceways, and enclosures must ensure electrical continuity; listed bonding fittings and jumpers are used where continuity is not assured.

Standard overcurrent device ratings: 15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90, 100, 110, 125, 150, 175, 200 A and upward.

The next-higher-standard-rating rule permits the next standard device above the calculated load when the load does not exceed 800 A and other conditions are met.

Continuous loads require the overcurrent device to be at least 125% of the continuous load plus 100% of noncontinuous load.

Short-circuit current rating (SCCR) of equipment must equal or exceed the available fault current at the point of installation; series-rated systems use listed combinations.

Fuses and circuit breakers must be selected so their interrupting rating is adequate for the available fault current at their line terminals.

Coordination is achieved by time-current curves: the upstream device should not trip before the downstream device for a fault in the downstream zone.

Overcurrent devices must be readily accessible, not exposed to physical damage, and installed in the orientation specified by the listing (breakers usually not upside down).

Series-rated equipment must be marked with the series combination rating; replacing a breaker with an unlisted type voids the rating.

Ground-fault protection of equipment (GFPE) at service levels (commonly 1000 A and above) limits damage from arcing ground faults; it does not replace GFCI.

Motor branch-circuit conductors are sized at 125% of the motor full-load current from the applicable table; the overload device is sized from the nameplate current.

Short-circuit and ground-fault protection for motors is sized from the FLC table using percentages by motor type and starting method; the next standard size may be used if the calculated size is not standard.

Motor overload protection protects the motor from overheating; it is separate from branch-circuit short-circuit protection and is set per nameplate or table values.

The motor disconnecting means must be in sight from the controller and motor, and within the distances specified; a lockable disconnect may be permitted where not in sight under conditions.

A controller is required for each motor; horsepower-rated switches or manual starters are used where permitted, and the controller must be capable of starting and stopping the motor.

A/C and refrigeration equipment: branch-circuit conductor ampacity is at least 125% of the rated-load current or the nameplate minimum circuit ampacity (MCA).

The nameplate maximum overcurrent protective device (MOP) rating may be used to size the branch-circuit protection for hermetic refrigerant motor-compressors.

Motor circuits require an equipment grounding conductor and bonding of the motor frame; flexible connections to motors must be listed for the purpose.

Motor full-load current tables differ for DC motors, single-phase, and polyphase; use the table matching the motor type rather than the nameplate FLA for conductor sizing.

Hazardous (classified) locations are classified by Class (I gases/vapors, II dusts, III fibers), Division or Zone, and Group; equipment must be listed for the specific classification.

Class I Division 1 requires explosionproof or intrinsically safe equipment; Division 2 requires equipment suitable for the location and non-arcing under normal conditions.

Bathrooms, garages, outdoors, crawl spaces, and kitchens have specific GFCI and receptacle requirements; receptacles near sinks and in damp locations need GFCI and appropriate covers.

Swimming pools, spas, and fountains require equipotential bonding of metal parts and specific receptacle distances and GFCI protection.

Health care facilities use redundant grounding and isolated power systems in critical care areas; receptacle types and grounding requirements are more stringent.

Assembly, theatrical, and motion picture locations have specific rules for stage wiring, portable switchboards, and grounding of portable equipment.

Service stations, bulk storage plants, and spray areas have classified-location boundaries; seals and conduit requirements apply at boundaries.

Solar photovoltaic systems require rapid shutdown provisions, listed DC-rated equipment, and labeling; PV conductors are considered energized at all times in sunlight.

Battery storage, electric vehicle supply equipment, and marinas have dedicated article requirements for disconnects, GFCI/GFPE, and bonding.

The NEC is organized into articles and chapters; Chapter 1–4 are general, Chapters 5–7 cover special occupancies, special conditions, and special equipment, and Chapter 9 contains tables and annexes.

Article 90 covers scope and enforcement; Article 100 defines terms such as 'listed', 'labeled', 'approved', and 'identified', which control code interpretation.

Lockout/tagout, PPE, and energized-work permits are covered by workplace safety standards (OSHA 1910 Subpart S) in addition to the NEC.

Arc flash risk assessment determines incident energy and arc flash boundary; PPE categories and approach boundaries are based on the calculated incident energy.

The NEC is not a design manual; it sets minimum requirements, and local amendments and the authority having jurisdiction (AHJ) may impose stricter rules.

Permits and inspections are required before covering work; the AHJ interprets the code and may require listed products and approved installation methods.

Approved equipment must be listed by a recognized testing laboratory; field modifications to listed equipment may void the listing.

Working clearances in front of electrical equipment are based on voltage, condition, and whether the equipment is live; the depth and width of the working space are specified.

Temporary wiring, flexible cords, and extension cords have restrictions on use as permanent wiring and on passing through walls, ceilings, or floors.

Read the drawing set in order: site plan, floor plans, power/lighting plans, panel schedules, single-line diagram, and specifications; cross-check panel schedules against the single-line.

Calculate dwelling general lighting load from floor area × 3 VA per square foot (about 33 VA/m²), then apply demand factors for the dwelling unit.

Small-appliance and laundry circuits: two or more 20 A small-appliance circuits at 1500 VA each plus one laundry circuit at 1500 VA in the standard method.

Range and dryer demand factors apply to household electric ranges and clothes dryers; the nameplate rating and table demand factors determine the load.

The optional dwelling calculation method permits a different load aggregation and may reduce service size; it must be applied consistently and documented.

Panel schedule checks: verify connected load, demand load, spare breaker spaces, bus rating, and that the main breaker equals or exceeds the calculated demand.

Single-line diagram checks: service voltage and phase, service disconnect rating, grounding electrode conductor, and feeder sizes to subpanels.

Plan symbols: duplex receptacle, GFCI receptacle, switch, junction box, panel, and motor connections must be matched to the legend; verify homerun counts and circuit numbers.

Verify available fault current on the utility or transformer data and confirm equipment SCCR and breaker interrupting ratings meet or exceed it.