Exam Cheat Sheet · Quick Reference

Oklahoma Limited Electrical Contractor

Oklahoma  ·  PSI Services Contractor

Verified, not estimated. Every figure below is drawn from the official exam structure we maintain — question counts, passing standard and topic weighting. Practice questions are grounded in the source law with statute citations. We omit any figure we can't verify rather than guess at it.
Total questions
100
Passing score
70%
Exam time
240 min
Administered by
PSI Services Contractor
Format
Reference materials allowed

Oklahoma State Portion 100 questions

General Knowledge 4 Q · 4%
a. Permits and Inspectionsb. Preservation of Structural Integrityc. Needs Analysis and Estimate
General Electrical Knowledge 10 Q · 10%
a. Voltage, Current, and Resistance in Series, Parallel, and Combination Circuitsb. Power Used in a Circuitc. Power Lost (called Heat Lost) in Any Circuitd. Fundamental AC Theorye. Fundamental Three-phase AC Theoryf. Cost of Power Used in a Circuitg. Troubleshooting and Test Systemsh. National Electrical Codebooki. Definitions Used by the NECj. Temporary Wiringk. Cranes and Hoistsl. Elevators and Escalators
Electrical Installation Requirements 10 Q · 10%
a. Approved Methods of Installation of Electrical Equipmentb. Approved Methods of Installation of Electrical Equipment in Excess of 600 volts
Services, Feeders, and Branch Circuits 10 Q · 10%
a. Servicesb. Voltage Drop for Branch Circuits or Feedersc. Services in Excess of 600 voltsd. Feederse. Outside Branch Circuits and Feedersf. Branch Circuitsg. Space-heating, Snow-melting, and Pipeheating Circuitsh. Air-conditioning and Refrigeration EquipmentSpace-heating, Snow-melting, and Pipe-heating Circuits
Overcurrent Protection 9 Q · 9%
a. NEC Overcurrent Protection RequirementNEC Overcurrent Protection Requirements
Grounding and Bonding 10 Q · 10%
a. General Requirementsb. Required Sizes of Grounding Electrode Conductorsc. Required Sizes of Equipment Grounding Conductors
Conductors and Cables 8 Q · 8%
a. Underground Conductors and Cablesb. Vertical Installationsc. Selecting Conductorsd. Armored Cable, Type ACe. Metal-clad Cable, Type MCf. Nonmetallic-sheathed Cable, Types NM, NMC, NMSg. Service Entrance Cables, Types SE and USEh. Underground Feeder and Branch Circuit Cable, Type UFi. Mineral Insulated, Type MIj. Flat Cable Assemblies, Type FC, and Flat Conductor Cable, Type FCCk. Medium Voltage Cable, Type MV
Raceways and Boxes 7 Q · 7%
a. General Raceway Requirementsb. General Box Requirementsc. Pull Boxesd. Conduit Fittingse. Type RMC (Rigid Metal Conduit)f. Type EMT (Electric Metallic Conduit)g. Type IMC (Intermediate Metal Conduit)h. Type RNC (Rigid Nonmetallic Conduit)i. Type FMC (Flexible Metal Conduit)j. Type LFMC (Liquid-tight Flexible Metal Conduit)k. Type FMT (Flexible Metallic Tubing)l. Type HDPE (High-density Polyethylene Conduit) +11 more
Special Occupancies and Equipment (Including Swimming Pools) 10 Q · 10%
a. Wiring in Class I, II, and III Hazardous Locationsb. Wiring in Commercial Garages and Fuel Dispensing Facilitiesc. Wiring in Bulk Storage Plants, Paint, and Spray Areasd. Special Occupanciese. Wiring in Health Facilities and Places of Assemblyf. Wiring of Mobile Home, Mobile Home Parks, RVs, and RV Parksg. Wiring of Floating Buildingsh. Wiring to Swimming Pools, Fountains, and Hot Tubs
Low Voltage, Alarms, Signaling Systems, and Communications 2 Q · 2%
a. Remote Control or Signaling Circuitsb. Communication Circuitsc. Equipment Operating at 50 volts or Lessd. Fiber Opticse. Photovoltaicsf. Remote Controlsg. Fire Alarmsh. Circuit Wiring for an Emergency Systemi. Communications Systems Wiring
Lighting and Signs 10 Q · 10%
a. Fixture Installationb. Fixture Groundingc. Fixture Wiringd. Fluorescent Fixturese. Fixture Construction Requirementsf. Recessed Fixturesg. Lighting Systems that Operate at Less Than 30 voltsh. Neon Lighting and Electric Signs
Safety 4 Q · 4%
a. Job Site Sanitationb. Responsibility for Providing Personal Protective Equipmentc. Excavation Safetyd. Emergency Action Planse. Safety Training Requirementsf. Ventilationg. First Aid Kit Requirementsh. Use of Personal Protective Equipmenti. Signs, Signals, and Barricadesj. Tools and Equipmentk. Laddersl. Workplace Illumination +6 more
Motors and Transformers 6 Q · 6%
a. Motors Used in Dwellingsb. Motor Branch Circuits in Industrial and Commercial Locationsc. Feeder Transformersd. Use of Transformers

Key Distinctions

Series circuitvsParallel circuit

In a series circuit total resistance is the sum of the individual resistances and total current equals the current in any other part of the circuit (IT = I1 = I2 = I3), while in a parallel circuit the voltage is the same across each branch, total current is the sum of the branch currents, and total resistance is always less than the resistance of any branch.

Ugly's Electrical References 2020, Series Circuits, Book Page 3
Branch-circuit OCPD sizing (210.20(A))vsFeeder conductor ampacity (215.2(A)(1))

Both use the noncontinuous load plus 125 percent of the continuous load, but 210.20(A) sets the minimum rating of the branch-circuit overcurrent device (with no noncontinuous load, 16 A × 1.25 = 20 A), while 215.2(A)(1) sets the minimum feeder conductor ampacity (80 A noncontinuous + 60 A × 1.25 = 155 A).

NEC 2023 Section 210.20(A)
Motor branch-circuit conductors (430.22)vsMotor feeder conductors (430.24)

Branch-circuit conductors to a single motor are sized at 125 percent of that motor's full-load current, while feeder conductors are sized at 125 percent of the largest motor's FLC plus the sum of the FLCs of the other motors.

NEC 2023 Section 430.22, Table 430.248
Dwelling unit minimum unit load (220.41)vsRetail occupancy general lighting unit load (Table 220.42(A))

Dwelling units use a minimum unit load of 3 volt-amperes per square foot, while retail occupancies use 1.9 volt-amperes per square foot (offices 1.3, automotive/dormitory/library 1.5, manufacturing/religious 2.2).

NEC 2023 Section 220.41
225.39(C) one-family dwelling unit supplyvs225.39(D) all other installations

A disconnect serving as a one-family dwelling unit's supply must be rated at least 100 amperes, but a feeder disconnect at a separate structure such as a detached garage (more than two circuits) requires a rating of not less than 60 amperes (one-circuit = 15 A minimum, two-circuit = 30 A minimum).

NEC 2023 Section 225.39(D)
Shielded or lead-covered conductors over 1000 VvsNonshielded conductors over 1000 V

Per NEC 305.5, shielded or lead-covered conductors shall not be bent to a radius less than 12 times the overall diameter, while nonshielded conductors have a minimum of 8 times the overall diameter.

NEC 2023 Section 305.5
Direct-buried cable over 1000 V AC through 22 kV (general conditions)vsOver 22 kV through 40 kV in rigid metal or intermediate metal conduit

Direct burial under general conditions requires 750 mm (30 in.) of cover, while circuits over 22 kV through 40 kV installed in RMC/IMC (Column 3) require only 150 mm (6 in.).

NEC 2023 Table 305.15(A)
MV cable support within 1.5 m (5 ft) of terminationsvsMV cable maximum 1.8 m (6 ft) between supports

Per NEC 315.40, Type MV cable terminated in equipment, pull boxes, or vaults must be secured within 1.5 m (5 ft) of terminations, and supports elsewhere may not exceed 1.8 m (6 ft) apart.

NEC 2023 Section 315.40
Green finish on a bonding jumper screwvsRed finish

Per NEC 250.28(B), when a main or system bonding jumper is a screw only, the screw shall be identified with a green finish (not red) visible with the screw installed.

NEC 2023 Section 250.28(B)
One continuous run between BOX A and BOX BvsRun with a conduit body added mid-run

NEC 358.26 (renumbered 358.24(B) in NEC 2023 and 2026) limits EMT to 360 degrees of bends between pull points; because a conduit body is a pull point, adding one lets each section on either side have up to 360 degrees of bends.

NEC 2023 Section 358.24(B)
Crane/hoist multi-motor supply conductors (610.14(E)(2))vsGeneral motor feeder sizing (430.24)

Crane conductors use the nameplate FLA of the largest motor (or group for a single crane motion) plus 50 percent of the next largest, while general motor feeders use 125 percent of the largest motor FLC plus 100 percent of the others.

NEC 2023 Section 610.14(E)(2)
Standard voltage designation 480Y/277vs'277/480'

NEC 220.5(A) lists 120, 120/240, 208Y/120, 240, 347, 480Y/277, 480, 600Y/347, and 600 volts as nominal voltages for load calculations; '277/480' is not a listed designation.

NEC 2023 Section 220.5(A)

Key Terms

Nominal system voltages for calculations (220.5(A)) NEC 2023 Section 220.5(A)
The voltages used for computing branch-circuit and feeder loads: 120, 120/240, 208Y/120, 240, 347, 480Y/277, 480, 600Y/347, and 600 volts.
Calculated floor area (220.5(C)) NEC 2023 Section 220.5(C)
For dwelling units, the floor area used in load calculations, which shall not include open porches or unfinished areas not adaptable for future use as a habitable room or occupiable space.
Minimum unit load, dwellings (220.41) NEC 2023 Section 220.41
In one-family, two-family, and multifamily dwellings, the load shall be not less than 3 volt-amperes per square foot (33 VA/m²).
General lighting unit load (Table 220.42(A)) NEC 2023 Table 220.42(A)
Volt-amperes per square foot assigned by occupancy for the minimum lighting load, including retail (which covers barber shops, beauty parlors, and stores) at 1.9 VA/sq ft, with the 125 percent continuous-load multiplier of 210.20(A) already included so no additional multiplier is required.
Receptacle outlet load (220.14(I)) NEC 2023 Section 220.14(I)
Receptacle outlets are calculated at not less than 180 volt-amperes for each single or each multiple receptacle on one yoke, so a duplex receptacle counts as 180 VA.
Structural addition load (220.16(A)) NEC 2023 Section 220.16(A)
Loads for structural additions to an existing dwelling unit, or for a previously unwired portion of an existing dwelling unit, are calculated in accordance with 220.14.
Small-appliance branch-circuit load (220.52(A)) NEC 2023 Section 220.52(A)
In each dwelling unit, 1500 volt-amperes is calculated for each 2-wire small-appliance branch circuit required by 210.11(C)(1).
Actual maximum demand method (220.87) NEC 2023 Section 220.87
A method of determining an existing load where maximum demand data for a 1-year period is available: the maximum demand at 125 percent plus the new load must not exceed the feeder ampacity or service rating, with feeder overcurrent protection per 240.4 and service overload protection per 230.90.
Kitchen equipment demand factor (Table 220.56) NEC 2023 Table 220.56
A permitted reduction for commercial kitchen equipment—65 percent for 6 or more units—provided the feeder or service calculated load is never less than the sum of the two largest kitchen equipment loads.
Non-dwelling receptacle demand factors (Table 220.47) NEC 2023 Table 220.47
Receptacle load computed under 220.14(I) is taken at 100 percent for the first 10 kVA and 50 percent for the remainder over 10 kVA.
Rounding of calculations (220.5(B)) NEC 2023 Section 220.5(B)
Calculations are permitted to be rounded to the nearest whole ampere, with decimal fractions smaller than 0.5 dropped (23.4 A may be used as 23 A).
Optional dwelling-unit calculation (220.82(A)) NEC 2023 Section 220.82(A)
Permitted for a dwelling unit whose total connected load is served by a single 120/240-volt or 208Y/120-volt set of 3-wire service or feeder conductors with an ampacity of 100 or greater.
Feeder tap not over 10 ft (240.21(B)(1)) NEC 2023 Section 240.21(B)(1)
A tap whose conductors, if they leave the enclosure or vault where the tap is made, must have an ampacity not less than one-tenth of the rating of the feeder overcurrent device, and not less than the combined calculated loads.
Elevator feeder demand factors (Table 620.14) NEC 2023 Table 620.14
Factors based on a 50 percent duty cycle applied to feeders serving multiple elevators: 1 = 1.00, 2 = 0.95, 3 = 0.90, 4 = 0.85, 5 = 0.82, 6 = 0.79, 7 = 0.77, 8 = 0.75, 9 = 0.73, 10 or more = 0.72.
Elevator supply voltage limit (620.3) NEC 2023 Section 620.3
Supply voltage for elevators, dumbwaiters, escalators, and moving walks shall not exceed 300 volts between conductors unless otherwise permitted by 620.3(A) through (C) for certain power, lighting, and heating/air-conditioning circuits.
Contact conductors (610.21(H)) NEC 2023 Section 610.21(H)
Crane/hoist contact conductors that shall not be used as feeders for any equipment other than the crane(s) or hoist(s) they are primarily designed to serve.
Crane working space (610.57) NEC 2023 Section 610.57
The working space in the direction of access to live parts likely to require examination, adjustment, servicing, or maintenance while energized shall be a minimum of 750 mm (2½ ft).
Temporary wiring for holiday decorative lighting (590.3(B)) NEC 2023 Section 590.3(B)
Temporary electric power and lighting installations permitted for a period not to exceed 90 days for holiday decorative lighting and similar purposes.
Assured equipment grounding conductor program (590.6(B)(2)) NEC 2023 Section 590.6(B)(2)
A temporary-wiring program under which all required tests on cord sets and receptacles are performed at intervals not exceeding 3 months.
Minimum MV conductor size (Table 315.12(A)) NEC 2023 Table 315.12(A)
Minimum conductor size by voltage rating for copper, aluminum, or copper-clad aluminum: 2001–5000 V = 8 AWG, 5001–8000 V = 6 AWG, 8001–15,000 V = 2 AWG, 15,001–28,000 V = 1 AWG, 28,001–35,000 V = 1/0 AWG.
Bored holes in wood members (300.4(A)(1)) NEC 2023 Section 300.4(A)(1)
Cable- or raceway-type wiring installed through bored holes in joists, rafters, or wood members must have the hole edge not less than 32 mm (1¼ in.) from the edges of the wood member.
Vegetation as support (230.10 and 225.26) NEC 2023 Section 230.10
Trees and other vegetation shall not be used to support overhead service conductors, service equipment, or overhead conductor spans for outside branch circuits and feeders—an absolute prohibition.
Dust-entrance prevention alternative (502.15) NEC 2023 Section 502.15
In Class II, Division 1 locations, where a raceway connects a dust-ignitionproof enclosure to one that is not, permitted alternatives to a permanent effective seal include a horizontal raceway not less than 3.05 m (10 ft) long, a vertical raceway not less than 1.5 m (5 ft) extending downward, or electrical sealing putty.
Transformer vault storage (450.48) NEC 2023 Section 450.48
Materials shall not be stored in transformer vaults, regardless of whether they are combustible or noncombustible.

Formulas to Know

Total resistance in a series circuitRT = R1 + R2 + R3 (e.g., 20 + 25 + 15 = 60 ohms)
Parallel circuit branch currents and total currentET = E1 = E2 = E3; each branch I = ET ÷ R; IT = I1 + I2 + I3 (120/60 + 120/80 + 120/120 = 2 + 1.5 + 1 = 4.5 A); total resistance is always less than any branch
Ohm's law power and resistanceP = E × I (120 V × 10 A = 1200 W); I = P ÷ E; R = E ÷ I, or R = E² ÷ P (14,400 ÷ 1200 = 12 ohms)
Three-phase kilowattsKW = (E × I × PF × 1.73) ÷ 1000 (460 × 52 × 0.80 × 1.73 ÷ 1000 ≈ 33 kW); 1.73 ≈ √3
Three-phase amperes when kW or HP is knownI = (KW × 1000) ÷ (E × PF × 1.73); I = (HP × 746) ÷ (E × %EFF × PF × 1.73)
Cost of operating an applianceCost = Watts × Hours Used × Rate per kWh ÷ 1000 (5000 W × 360 h × $0.15 ÷ 1000 = $270 per month)
Continuous-load sizing for branch circuits and feedersBranch OCPD rating ≥ noncontinuous load + 125% × continuous load (continuous only: 16 × 1.25 = 20 A); feeder ampacity ≥ noncontinuous + 125% × continuous (80 + 60 × 1.25 = 155 A; 30 + 100 × 1.25 = 155 A)
Motor conductor sizing (branch circuit and feeder)Branch-circuit conductors = 125% × motor FLC from the FLC tables (28 A × 1.25 = 35 A); feeder = (125% × largest motor FLC) + sum of other motor FLCs (65 × 1.25 + 40 = 121.25 A; 15.2 × 1.25 + 15.2 + 15.2 = 49.4 A)
Crane/hoist power supply conductor ampacityLargest motor (or group for a single crane motion) nameplate FLA + 50% of next largest (40 + 0.5 × 30 = 55 A; 40 + 0.5 × 20 = 50 A)
Non-dwelling receptacle demand load and lighting load by areaReceptacle demand = first 10 kVA at 100% + remainder at 50% (10,000 + 8,000 × 0.5 = 14,000 VA); lighting = area × unit load (5,000 sq ft × 1.9 VA = 9,500 VA)
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