Exam Cheat Sheet · Quick Reference

Oklahoma Unlimited 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%
Purpose and scope of the NEC (practical safeguarding of persons and property)Installations covered and not covered by the NECNEC code arrangement and chapter organizationMandatory vs. permissive vs. explanatory rules (shall/shall not vs. shall be permitted)Authority having jurisdiction (AHJ) enforcement powers and special permissionExamination and listing of equipment for safetyWiring planning for future expansion and limiting circuits in enclosuresUnits of measurement (SI and inch-pound dual system, hard vs. soft conversion)
General Electrical Knowledge 10 Q · 10%
Ohm's Law formulas and calculations (voltage, current, resistance, power)Series, parallel, and combination circuit analysisAC electrical formulas for single-phase and three-phase systems (kW, kVA, HP, amperes)Voltage drop calculations for single-phase and three-phase circuitsGrounded conductor identification and use (NEC Article 200)NEC Article 300 general wiring methods and materials requirementsPower factor, impedance, reactance, and capacitance in AC circuitsCommon electrical distribution systems and conductor color coding
Electrical Installation Requirements 10 Q · 10%
Branch-circuit ratings, conductor sizing, and overcurrent protection requirementsGFCI and AFCI protection requirements by location and occupancy typeDwelling unit and non-dwelling receptacle and lighting outlet placement requirementsBranch-circuit and feeder load calculations including demand factorsVoltage drop calculations for single-phase and three-phase circuitsAmpacity correction and adjustment factors for ambient temperature and conductor fillUnderground installation minimum cover requirements and wiring method selectionGeneral wiring methods: physical protection, conductor support, raceway installation, and working space clearances
Services, Feeders, and Branch Circuits 10 Q · 10%
Branch-circuit ratings, conductor sizing, and overcurrent protection (Articles 210, 215, 230)Load calculations for branch circuits, feeders, and services using demand factors (Article 220)GFCI and AFCI protection requirements by location and occupancy typeService entrance requirements: number of services, disconnecting means, and overcurrent protectionConductor ampacity correction and adjustment factors for temperature and conduit fillVoltage drop calculations for single-phase and three-phase circuitsOverhead and underground service conductor clearances, wiring methods, and installation requirementsMotor branch circuit and feeder conductor sizing and overcurrent protection
Overcurrent Protection 9 Q · 9%
Standard ampere ratings for fuses and inverse time circuit breakers (Table 240.6(A))Conductor overcurrent protection requirements by wire size and material (240.4(D))Feeder tap rules and maximum tap conductor lengths (240.21(B))Motor branch-circuit overcurrent device maximum ratings by motor type (NEC Table 430.52)Motor overload protection placement and running overload unit requirementsArc energy reduction requirements for high-ampere overcurrent devices (240.67, 240.87)Short-circuit current calculation procedure including transformer let-through currentOvercurrent protection for systems over 1000 volts — circuit breaker and power fuse requirements (Article 245)
Grounding and Bonding 10 Q · 10%
Grounding electrode system types and installation requirements (NEC 250.52–250.54)Grounding electrode conductor sizing and installation (NEC Table 250.66)Equipment grounding conductor types, sizing, and identification (NEC 250.118–250.122)Main bonding jumper and system bonding jumper requirements and sizing (NEC Table 250.102(C)(1))Bonding of services, piping systems, and structural metal (NEC 250.92–250.104)Grounding of separately derived systems and generators (NEC 250.30, 250.34, 250.35)Permitted connection methods for grounding and bonding conductors (NEC 250.8, 250.70)Surge-protective device (SPD) and surge arrester grounding connection requirements (NEC Article 242)
Conductors and Cables 8 Q · 8%
Conductor insulation types, temperature ratings, and application provisions (NEC Article 310 Table 310.4)Ampacity tables for conductors in raceways, cables, and free air (Tables 310.16–310.21)Ampacity correction factors for ambient temperature and adjustment factors for more than three current-carrying conductorsConductor sizing, material, and stranding requirements (minimum sizes, copper vs. aluminum, AA-8000 series)Cable type uses permitted and uses not permitted (NM, NMC, MC, AC, SE, USE, UF, MI, TC, ITC, MV, and specialty types)Securing, supporting, and bending radius requirements for specific cable typesConduit fill calculations and maximum number of conductors in various raceway typesMedium voltage (Type MV) cable construction, shielding, insulation levels, and ampacity
Raceways and Boxes 7 Q · 7%
Conduit and tubing types: permitted uses, restrictions, and installation requirements (RMC, IMC, EMT, FMC, LFMC, FMT, PVC, RTRC, HDPE, LFNC, ENT, NUCC)Box fill calculations: conductor, clamp, device, fitting, and equipment grounding conductor volume allowancesPull and junction box sizing: straight pull and angle/U-pull minimum dimension requirementsSecuring and supporting requirements for raceways, conduit, and tubing (support intervals and fastening distances)Box and enclosure selection and installation: types, damp/wet location requirements, flush mounting, and accessibilityCable tray systems: types, permitted wiring methods, fill calculations, ampacity, grounding, and bondingWireways, auxiliary gutters, busways, and specialty raceway systems: uses permitted, conductor fill limits, and support requirementsGrounding and bonding of metallic raceways, boxes, and enclosures
Special Occupancies and Equipment (Including Swimming Pools) 10 Q · 10%
Hazardous location classification — Class I, II, and III, Divisions 1 and 2Zone classification system — Zone 0, 1, 2, 20, 21, and 22 locationsWiring methods and sealing requirements in hazardous locationsHealth care facility essential electrical systems and patient care space wiringMotor fuel dispensing, commercial garages, aircraft hangars, and bulk storage plant electrical requirementsElevators, cranes, hoists, and electric vehicle power transfer systemsMobile homes, recreational vehicles, marinas, and temporary installationsTheaters, assembly occupancies, and entertainment venue wiring requirements
Low Voltage, Alarms, Signaling Systems, and Communications 2 Q · 2%
Fire alarm circuit types: NPLFA vs. PLFA power sources, branch circuit requirements, and overcurrent protectionFire alarm cable types, ratings, and application requirements (FPLP, FPLR, FPL, NPLFP, NPLFR, NPLF) including plenum, riser, and general-purpose installationsCircuit integrity (CI) cables and fire-resistive cable systems for survivability of critical circuitsClass 2 and Class 3 power-limited circuit wiring methods, power source requirements, and separation from other circuitsClass 1 power-limited remote-control and signaling circuit requirements, overcurrent protection, and conductor sizingCommunications system grounding, bonding, and primary protector requirements (Articles 800, 805, 820, 830)Cable types and installation methods for communications, CATV coaxial, optical fiber, and broadband systems including plenum/riser/general-purpose ratings and substitution hierarchiesClass 4 fault-managed power systems: transmitter/receiver requirements, fault management, separation rules, and cable types
Lighting and Signs 10 Q · 10%
Luminaire location requirements (wet, damp, corrosive, bathtub/shower zones, clothes closets)Recessed luminaire installation (Type IC vs. non-IC, thermal protection, clearances from insulation and combustible material)Lighting track installation requirements, permitted/prohibited locations, and construction standardsLuminaire support methods and grounding requirementsDisconnecting means for fluorescent and LED luminaires with double-ended lampsElectric sign and outline lighting branch circuit requirements, ratings, and disconnecting meansGrounding, bonding, and enclosure requirements for electric signs and outline lighting systemsNeon secondary-circuit wiring methods (1000 volts or less and over 1000 volts)
Safety 4 Q · 4%
Electrical hazard recognition and shock protection boundaries (limited and restricted approach)Lockout/tagout procedures and establishing an electrically safe work conditionArc-flash hazard analysis, equipment labeling, and PPE categoriesPersonal protective equipment selection, use, and employer payment requirementsGround-fault circuit interrupter (GFCI) and assured equipment grounding conductor programFire protection and prevention on construction sites (extinguisher ratings, flammable liquid storage, fire prevention plans)Confined space entry procedures, atmospheric testing, and permit requirementsOccupational health controls (noise exposure limits, airborne contaminant PELs, ventilation, asbestos handling)
Motors and Transformers 6 Q · 6%
Motor branch-circuit conductor sizing (125% rule, NEC Article 430 Part II)Motor branch-circuit short-circuit and ground-fault protection ratings and settings (Table 430.52)Motor overload protection requirements and trip current percentages (NEC 430.32)Motor disconnecting means types, ratings, and location requirements (NEC 430.109–430.112)Motor controller ratings, marking, and application requirements (NEC 430.83)Transformer overcurrent protection sizing for primary and secondary (NEC 450.3, Tables 450.3(A) and 450.3(B))Transformer sizing calculations and full-load current determination (single-phase and three-phase)Locked-rotor code letters and locked-rotor current calculations (Table 430.7(B), Tables 430.251(A) and 430.251(B))Delta and wye transformer connections (line vs phase voltage and current, neutral current, balancing)

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 part of the circuit (IT = I1 = I2 = I3), while in a parallel circuit the voltage is the same across all branches, total current is the sum of the branch currents, and total resistance is always less than the resistance of any single branch.

Ugly's Electrical References 2020, Series Circuits, Book Page 3
Single-phase motor on a 2-wire ungrounded supply circuitvsThree-phase motor

Per Table 430.37 a single-phase AC or DC motor on a 2-wire ungrounded circuit needs only one running overload unit, placed in either conductor, whereas a 3-phase motor requires three overload units, one in each phase.

NEC 2023 Table 430.37
3 percent voltage drop (branch circuit or feeder alone)vs5 percent total voltage drop (feeders plus branch circuits)

The informational notes recommend sizing a branch circuit (210.19) or a feeder (215.2(A)(2)) so the drop at the farthest outlet does not exceed 3 percent, while the combined drop on feeders plus branch circuits to the farthest outlet should not exceed 5 percent; both are recommendations, not requirements.

NEC 2023 Section 210.19, Informational Note
Copper overhead service conductorsvsAluminum/copper-clad aluminum overhead service conductors

Per 230.23(B) overhead service conductors shall not be smaller than 8 AWG copper, but aluminum or copper-clad aluminum may not be smaller than 6 AWG.

NEC 2023 Section 230.23(B)
Outside branch-circuit/feeder open conductor spans up to 15 m (50 ft)vsSpans longer than 15 m (50 ft)

Per 225.6(A) spans up to 50 ft require a minimum 10 AWG copper (8 AWG aluminum), while longer spans require 8 AWG copper (6 AWG aluminum) unless supported by a messenger wire.

NEC 2023 Section 225.6(A)
Standard ampere ratings for fuses onlyvsStandard ampere ratings for both fuses and inverse time circuit breakers

Per 240.6(A), 1, 3, 6, and 601 amperes are additional standard ratings for fuses only, while ratings such as 15, 20, …, 110, 125, …, 6000 amperes in Table 240.6(A) apply to both fuses and inverse time circuit breakers.

NEC 2023 Section 240.6(A) and Table 240.6(A)
Shielded or lead-covered conductors over 1000 voltsvsNonshielded conductors over 1000 volts

Per 305.5 the minimum bending radius during or after installation is 12 times the overall diameter for shielded or lead-covered conductors, but only 8 times the overall diameter for nonshielded conductors.

NEC 2023 Section 305.5
Type MV-90 cablevsType MV-105 cable

Per Table 315.10(A), MV-90 has a maximum operating temperature of 90°C (suitable for dry or wet locations) while MV-105 is rated 105°C.

NEC 2023 Table 315.10(A)
Feeder disconnect for a one-family dwelling unit supply — 225.39(C)vsFeeder/branch-circuit disconnect at other structures — 225.39(D)

225.39(C) requires a minimum 100-ampere, 3-wire rating where the supply is to a one-family dwelling unit, while 225.39(D) requires at least 60 amperes for all other installations (with 15 A minimum for one-circuit and 30 A minimum for two-circuit installations), so a detached garage fed from the dwelling falls under the 60-ampere minimum.

NEC 2023 Section 225.39(C)
3-wire feeders sharing a common neutralvs4-wire or 5-wire feeders sharing a common neutral

Per 215.4(A), up to three sets of 3-wire feeders are permitted on a common neutral, but only two sets of 4-wire or 5-wire feeders.

NEC 2023 Section 215.4(A)
Direct-buried residential 120-volt GFCI-protected branch circuit (max 20 A OCPD)vsDirect-buried cable over 1000 V AC through 22 kV

Table 300.5(A) Column 4 permits only 12 inches of cover for a 120-volt-or-less residential branch circuit with GFCI protection and maximum 20-ampere overcurrent protection (versus the standard 24-inch depth), while Table 305.15(A) requires 750 mm (30 in.) of cover for direct-buried cable over 1000 V AC through 22 kV under general conditions.

NEC 2023 Table 300.5(A), Column 4
Motor overload maximum, motors without those markings: 115 percent of FLCvsMotor overload maximum, service factor ≥ 1.15 or temperature rise ≤ 40°C: 125 percent of FLC

Per 430.32(A)(1) a separate overload device is rated or set to trip at no more than 115 percent of nameplate full-load current for motors without those markings, and no more than 125 percent for motors with a marked service factor of 1.15 or greater or a marked temperature rise of 40°C or less. Both are maximums, not a range (30 A nameplate: 34.5 A or 37.5 A maximum).

NEC 2023 Section 430.32(A)(1), 430.32(C)

Key Terms

Assured equipment grounding conductor program (temporary wiring) NEC 2023 Section 590.6(B)(2)
A program under 590.6(B)(2) in which all required tests on cord sets and receptacles must be performed at intervals not exceeding 3 months.
Temporary wiring for holiday decorative lighting NEC 2023 Section 590.3(B)
Per 590.3(B), temporary electric power and lighting installations are permitted for a period not to exceed 90 days for holiday decorative lighting and similar purposes.
Grounding-type receptacle (temporary installations) NEC 2023 Section 590.4(D)(1)
Per 590.4(D)(1), all receptacles used in temporary installations must be of the grounding type, and all branch circuits must include a separate equipment grounding conductor unless installed in a continuous metal raceway or cable qualifying as an equipment grounding conductor.
Main bonding jumper / system bonding jumper that is a screw only NEC 2023 Section 250.28(B)
Per 250.28(B), when the bonding jumper is a screw only, the screw must be identified with a green finish (not red) that is visible with the screw installed.
Contact conductors (cranes and hoists) NEC 2023 Section 610.21(H)
Per 610.21(H), crane contact conductors 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 in direction of access to live parts NEC 2023 Section 610.57
Per 610.57, the working space in the direction of access to live parts likely to require examination, adjustment, servicing, or maintenance while energized must be a minimum of 750 mm (2½ ft).
Feeder demand factors for elevators (Table 620.14) NEC 2023 Table 620.14
Demand factors based on a 50 percent duty cycle applied to elevators on a single feeder: 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, and 10 or more = 0.72.
Elevator supply voltage limit NEC 2023 Section 620.3
Per 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.
Type MV cable support requirements NEC 2023 Section 315.40
Per 315.40, Type MV cable terminated in equipment or installed in pull boxes or vaults must be secured and supported within 1.5 m (5 ft) of terminations and at a maximum of 1.8 m (6 ft) between supports.
Minimum conductor size for Type MV cable (Table 315.12(A)) NEC 2023 Table 315.12(A)
Minimum copper, aluminum, or copper-clad aluminum sizes by voltage: 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.
Point of attachment (overhead service conductors) NEC 2023 Section 230.26
Per 230.26, the point where overhead service conductors attach to a building or structure must provide the clearances of 230.9 and 230.24 and in no case be less than 3.0 m (10 ft) above finished grade.
Optional calculation for a dwelling unit NEC 2023 Section 220.82(A)
Per 220.82(A), the optional method applies only where the 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 amperes or greater.
Fixed electric space-heating load NEC 2023 Section 220.51
Per 220.51, fixed electric space-heating loads are calculated at 100 percent of the total connected load, and in no case may the feeder or service load rating be less than the rating of the largest branch circuit supplied.
Pull point (EMT bend limit) NEC 2023 Section 358.24(B)
Bends are limited to 360 degrees between pull points; a conduit body is a pull point, so each section between pull points may have up to 360 degrees of bends. Section number: 358.24(B) in NEC 2023 and 2026; 358.26 in NEC 2020 and 2017.
Feeder tap not over 10 ft (240.21(B)(1)) NEC 2023 Section 240.21(B)(1)
Tap conductors that 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, in addition to meeting the other 240.21(B)(1) requirements such as not being less than the combined calculated loads.
Angle pull (junction box sizing, 314.28(A)(2)) NEC 2023 Section 314.28(A)(2)
For angle pulls, the distance from a raceway entry to the opposite wall must be at least six times the trade size of the largest raceway, increased by the sum of the diameters of all other raceway entries in the same row on the same wall.

Formulas to Know

Total resistance — series circuit and equal resistors in parallelSeries: RT = R1 + R2 + R3 (e.g., 20 + 25 + 15 = 60 Ω). Equal resistors in parallel: RT = R ÷ n (e.g., 18 Ω ÷ 3 = 6 Ω, then add series resistance: 2 + 6 = 8 Ω; I = 24 V ÷ 8 Ω = 3 A).
Parallel circuit voltage and currentET = E1 = E2 = E3; each branch I = E ÷ R; IT = I1 + I2 + I3 (e.g., 120/60 + 120/80 + 120/120 = 2 + 1.5 + 1 = 4.5 A); RT is always less than any branch resistance.
Ohm's law — power, current, resistanceP = E × I (120 V × 10 A = 1200 W); I = P ÷ E (1200 ÷ 120 = 10 A); R = E ÷ I (120 ÷ 10 = 12 Ω) or R = E² ÷ P (14,400 ÷ 1200 = 12 Ω).
Three-phase kilowattsKW = (E × I × PF × 1.73) ÷ 1000 (e.g., 460 × 52 × 0.80 × 1.73 ÷ 1000 ≈ 33 kW); 1.73 is √3, accounting for the 120-degree phase relationship.
Three-phase amperes from kW or horsepowerI = (KW × 1000) ÷ (E × PF × 1.73); I = (HP × 746) ÷ (E × %EFF × PF × 1.73).
Cost of operating an electrical applianceCost = (Watts × Hours Used × Rate per kWh) ÷ 1000 (e.g., 5000 W × (12 hr × 30 days) × $0.15 ÷ 1000 = $270 per month).
Crane/hoist power supply conductor minimum ampacity (610.14(E)(2))Minimum ampacity = nameplate FLA of the largest motor (or group of motors for any single crane motion) + 50% of the nameplate FLA of the next largest motor (e.g., 40 + 0.5 × 30 = 55 A; 40 + 0.5 × 20 = 50 A).
Continuous load sizing — feeder/branch conductors and overcurrent deviceConductor ampacity ≥ noncontinuous load + 125% of continuous load (215.2(A)(1): 80 + 60 × 1.25 = 155 A; 30 + 100 × 1.25 = 155 A). Branch-circuit OCPD rating ≥ 125% of continuous load (210.20(A): 16 × 1.25 = 20 A).
Motor conductor, feeder, overload and breaker sizingBranch-circuit conductors = 125% of motor FLC (430.22(A): 65 A × 1.25 = 81.25 A). Feeder (430.24) = 125% of largest motor FLC + FLC of all others (15.2 × 1.25 + 15.2 + 15.2 = 49.4 A). Overload = 115% of FLC (up to 125% for SF ≥ 1.15 or rise ≤ 40°C). Inverse time breaker = 250% of FLC for a single-phase motor, next standard size up if the motor won't start (50 A × 2.5 = 125 A → 150 A), but never over 400% of FLC for currents of 100 A or less (60 A × 4 = 240 A max).
Apparent power from kW and power factor; parallel-set ampacity; conduit fill checkkVA = kW ÷ PF (200 kW ÷ 0.8 = 250 kVA). Parallel conductors: total ampacity = single-conductor ampacity × number of sets (350 kcmil Cu at 90°C = 350 A; 2 sets = 700 A). Conduit fill for 3 or more conductors = 40% maximum; area = πr², so 3 × π(0.125)² ≈ 0.0368 in² in a 1-in. ID conduit (0.7854 in²) ≈ 4.7% fill.
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