Exam Cheat Sheet · Quick Reference
Oklahoma Residential 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
80
Passing score
70%
Exam time
210 min
Administered by
PSI Services Contractor
Format
Reference materials allowed
Oklahoma State Portion 80 questions
General Knowledge
4 Q · 5%
NEC purpose, scope, and installations covered vs. not coveredNEC code arrangement and chapter organizationMandatory, permissive, and explanatory rule languageAuthority having jurisdiction (AHJ) enforcement and special permissionUnits of measurement: SI metric and inch-pound dual system in the NECField trade terms versus official NEC terminologyElectrical symbols used in drawings and diagramsU.S. and metric unit conversions and equivalents
General Electrical Knowledge
12 Q · 15%
Ohm's Law formulas and calculations (voltage, current, resistance, power)Series, parallel, and combination circuit analysisVoltage drop calculations for single-phase and three-phase circuitsElectrical formulas for amperes, kilowatts, kVA, and horsepower (single-phase and three-phase)Grounded conductor identification, use, and terminal marking (NEC Article 200)General wiring methods requirements: conductor installation, protection, and raceway rules (NEC Article 300)Transformer calculations: sizing, primary/secondary amperes, and connectionsSwitches, receptacles, panelboards, and switchboards: ratings, installation, and grounding requirements
Electrical Installation Requirements
10 Q · 12%
Branch-circuit ratings, conductor sizing, and overcurrent protection requirementsGFCI protection requirements by location and occupancy typeAFCI protection requirements for dwelling units and other occupanciesDwelling unit receptacle outlet placement and spacing requirementsRequired lighting outlets and switching in dwelling units and all occupanciesUnderground installation minimum cover requirements by wiring methodConduit and raceway support spacing and physical protection of conductorsBranch-circuit, feeder, and service load calculations including demand factors
Services, Feeders, and Branch Circuits
10 Q · 12%
Service conductor sizing, ampacity, and minimum size requirementsService disconnecting means: location, rating, and number of disconnectsOvercurrent protection for services and feedersBranch-circuit, feeder, and service load calculations using demand factorsVoltage drop calculations for single-phase and three-phase circuitsOverhead service conductor clearances from grade, roofs, and building openingsGrounding electrode conductor and bonding jumper sizing for AC systemsOutside feeder and branch circuit requirements including clearances and disconnecting means
Overcurrent Protection
8 Q · 10%
Conductor overcurrent protection and ampacity requirements (NEC 240.4, small conductor limits by AWG)Standard ampere ratings for fuses and circuit breakers (NEC Table 240.6(A))Location of overcurrent protective devices in circuits, including feeder and transformer secondary tap rulesAccessibility and placement restrictions for overcurrent devices (height, bathrooms, closets, stairways)Fuse types and requirements: plug fuses, Type S, Edison-base, and cartridge fusesCircuit breaker requirements: marking, indicating, nontamperable, series ratings, and arc energy reduction (240.87)Motor branch-circuit overcurrent protection maximum ratings by motor and device type (Table 430.52)Short-circuit current ratings and calculations for panelboards, switchgear, and protective devices
Grounding and Bonding
8 Q · 10%
Grounding electrode types and installation requirements (NEC 250.52, 250.53)Grounding electrode conductor sizing using Table 250.66Equipment grounding conductor types, sizing, and identification (Table 250.122)Main bonding jumper and system bonding jumper requirements and sizing (Table 250.102(C)(1))Service grounding connections and load-side grounding restrictionsBonding of metal water piping, gas piping, and structural metalSeparately derived system grounding and bondingPermitted connection methods for grounding and bonding conductors
Conductors and Cables
4 Q · 5%
Conductor insulation types, temperature ratings, and permitted applications (THHN, THWN, RHW, XHHW, TW, etc.)Ampacity tables for conductors in raceways, cables, and free air (Tables 310.16 and 310.17)Ambient temperature correction factors and adjustment factors for more than three current-carrying conductorsConductor material, minimum size, stranding, and parallel conductor requirementsNonmetallic-sheathed cable (Types NM and NMC): permitted uses, installation, securing, and ampacity limitationsType AC and Type MC cable: permitted uses, installation, securing, bending radius, and fittingsService-entrance cable (Types SE and USE) and underground feeder cable (Type UF): uses permitted, restrictions, and ampacityConductor properties: DC resistance, circular mil area, dimensions of insulated conductors, and conduit fill calculations
Raceways and Boxes
6 Q · 8%
Conduit fill calculations and conductor count limits by raceway type (EMT, RMC, IMC, PVC, FMC, LFMC, LFNC, ENT)Securing and support intervals for each raceway typePermitted and prohibited uses for each raceway type by location and conditionBox fill calculations: conductor, clamp, device, and equipment grounding conductor volume allowancesBox sizing and dimensions for outlet, device, pull, and junction boxesBox support methods and mounting requirementsConduit bending requirements: bend radius and maximum degrees per runCabinets and cutout boxes: wire-bending space, conductor deflection, and spacing requirements
Special Occupancies and Equipment
8 Q · 10%
Swimming pools, spas, and hot tubs: GFCI/SPGFCI protection requirements and equipotential bondingSwimming pools: overhead conductor clearances and underwater luminaire installationMobile and manufactured homes: power supply, disconnecting means, and branch-circuit requirementsRecreational vehicles and RV parks: feeder assemblies, receptacle configurations, and groundingHazardous (classified) locations: Class I, II, and III location classification and protection techniquesHealth care facilities: essential electrical systems, patient care space wiring, and grounding requirementsFire pump power sources, disconnecting means, and wiring requirementsAgricultural buildings: wiring methods, equipotential planes, and GFCI requirements
Low Voltage, Alarms, Signaling Systems, and Communications
4 Q · 5%
Fire alarm circuit types: NPLFA vs. PLFA power sources, branch circuit requirements, and overcurrent protectionFire alarm cable types, listings, and installation applications (FPL, FPLR, FPLP, NPLF, NPLFR, NPLFP)Separation and mixing rules for fire alarm, power, Class 1, and communications conductors in raceways and enclosuresGrounding and bonding of communications system cables, primary protectors, and intersystem bonding terminationCommunications cable types and installation applications by location (CMP, CMR, CMG, CM, CMX) in plenums, risers, and general spacesAntenna system installation: conductor sizing, clearances, supports, discharge units, and groundingCATV and broadband communications system coaxial cable grounding, power limitations, and cable substitutionsLow-voltage lighting system requirements: voltage limitations, isolation, secondary circuit grounding, and branch circuit ratings
Lighting and Signs
2 Q · 2%
Luminaire installation requirements for specific locations (wet, damp, closets, bathtub/shower zones)Recessed luminaire clearances, thermal protection, and Type IC vs. non-IC insulation contact rulesLighting track installation, load ratings, permitted/prohibited locations, and construction requirementsLuminaire support methods, pole-mounted luminaires, and outlet box support requirementsGrounding and bonding of luminaires and lighting equipmentDisconnecting means requirements for fluorescent and LED luminaires with double-ended lampsElectric sign and outline lighting branch circuit requirements, disconnecting means, and grounding/bondingNeon secondary-circuit wiring methods for signs (1000 volts or less vs. over 1000 volts) and transformer/power supply requirements
Safety
4 Q · 5%
Lockout/tagout procedures and establishing an electrically safe work conditionPersonal protective equipment selection and requirements for electrical workArc-flash hazard assessment, boundaries, and equipment labelingShock protection boundaries and minimum approach distancesGround-fault circuit interrupter (GFCI) and assured equipment grounding conductor programEmployer and employee responsibilities for electrical safetyFirst aid availability and medical services requirements for electrical workConfined and enclosed space entry procedures for electrical workers
Key Distinctions
Mandatory NEC Rule ('shall/shall not')vsInformational Note
Mandatory rules using 'shall' or 'shall not' are enforceable, while Informational Notes are explanatory only and are NOT enforceable requirements.
NEC 90.5(A)NEC Chapters 1–4vsNEC Chapters 5–7
Chapters 1–4 apply generally to ALL electrical installations, while Chapters 5–7 apply only to special occupancies, special equipment, or other special conditions and may supplement or modify Chapters 1–4.
Article 90.3NEC Chapter 8 (Communications Systems)vsNEC Chapters 1–7
Chapter 8 covers communications systems and is NOT subject to Chapters 1–7 except where specifically referenced in Chapter 8, making it effectively self-contained.
Article 90.310-ft Feeder Tap Rulevs25-ft Feeder Tap Rule (one-third rule)
For taps not over 10 ft, conductor ampacity must meet combined calculated loads AND the downstream overcurrent device rating; the 25-ft tap uses the one-third rule instead.
NEC Handbook, Section 240.21(B)(1)Continuous Load (125% factor)vsNoncontinuous Load (no uprating)
Branch-circuit conductor ampacity must be at least 125% of the continuous load portion, while the noncontinuous load portion is added at 100% with no multiplier.
NEC 210.19(A)(1)Multioutlet Branch Circuit Ratings (standard list)vsIndividual Branch Circuit Rating
Multioutlet branch circuits are limited to the standard ratings of 10, 15, 20, 30, 40, and 50 amperes, whereas individual branch circuits can be rated based on the actual load served.
NEC 210.18Type SO Flexible CordvsType SJ Flexible Cord
Type SO is rated for extra-hard usage in damp locations at 600 V, while Type SJ (Junior hard service) is rated for hard usage (not extra-hard) in damp locations.
NEC Table 400.4Plug Fuses ≤15 AvsPlug Fuses >15 A
Fuses rated 15 amperes and lower are physically identified by a hexagonal window, cap, or prominent part to distinguish them from higher-rated fuses.
NEC 2023, Section 240.50(C)Equipment Grounding Conductor Color (flexible cord)vsAll Other Conductor Colors
Equipment grounding conductors in flexible cords must be continuously green or green with one or more yellow stripes and cannot be used for any other purpose.
NEC 250.119(D), NEC 400.23Bored Hole Edge Distance (1¼ in.)vsSteel Plate Protection (1/16 in. thick)
Cable/raceway holes must be at least 1¼ in. from the edge of the wood member; when that distance cannot be maintained, a steel plate at least 1/16 in. thick must protect the cable instead.
NEC 300.4(A)(1)Direct-Buried Cable Minimum Cover (24 in.)vsVertical Raceway Conductor Support (100 ft max)
Direct-buried cables in general locations require a minimum cover of 24 in., while conductors in vertical raceways (18 AWG–8 AWG copper) must be supported at intervals not exceeding 100 ft.
Table 300.5(A)AFCI Protection Required LocationsvsAFCI Max Wiring Length to First Outlet (14 AWG)
AFCI protection is required for all 120 V, single-phase, 15- and 20-ampere branch circuits in bedrooms; when using an outlet branch-circuit AFCI with supplemental arc protection, the wiring from the overcurrent device to the first outlet must not exceed 50 ft for 14 AWG.
NEC 210.12(B)Key Terms
Purpose of the NEC (NEC 90.2(A)) NEC 90.2(A)
The NEC exists for the practical safeguarding of persons and property from hazards arising from the use of electricity; it is not a design specification or instruction manual for untrained persons.
NEC Measurement System of Preference (NEC 90.9(A)/(B)) NEC 90.9(A), 90.9(B)
Metric (SI) units are the preferred measurement system; SI units appear first in the Code, with inch-pound units immediately following in parentheses.
Installations NOT Covered by NEC (Article 90.2(D)) Article 90.2(D)
The NEC does not cover installations in ships, aircraft, railway rolling stock, watercraft (other than floating buildings), or automotive vehicles other than mobile homes and recreational vehicles.
Informational Notes — Not Enforceable (NEC 90.5(C)) NEC 90.5(C)
Informational Notes in the NEC are for explanatory or reference purposes only and are not enforceable as Code requirements.
NEC Intended for Mandatory Adoption (NEC 90.4(A)) NEC 90.4(A)
The NEC is intended to be suitable for mandatory application by governmental bodies that exercise legal jurisdiction over electrical installations, including signaling and communications systems, and for use by insurance inspectors.
Branch-Circuit Voltage Limit in Dwelling Units (NEC 210.6(A)) NEC 210.6(A)
In dwelling units, voltage shall not exceed 120 V nominal between conductors supplying cord-and-plug-connected loads of 1440 VA or less.
Minimum Household Range Branch-Circuit Rating (NEC 210.19(C)) NEC 210.19(C)
Branch circuits supplying household ranges rated 8¾ kW or more must have a minimum branch-circuit rating of 40 amperes.
Plug Fuse Identification — Hexagonal (NEC 240.50(C)) NEC 2023, Section 240.50(C)
Plug fuses rated 15 amperes and lower must be identified by a hexagonal configuration of the window, cap, or other prominent part to distinguish them from higher-rated fuses.
Feeder Tap — Not Over 10 ft (NEC 240.21(B)(1)) NEC Handbook, Section 240.21(B)(1)
For feeder taps not exceeding 10 ft enclosed in a raceway, conductor ampacity must be at least the combined calculated loads supplied and not less than the rating of the downstream overcurrent device.
Voltage Drop Recommendation — Branch Circuits (NEC 210.19 Informational Note) NEC 210.19, Informational Note
The NEC recommends that branch-circuit voltage drop not exceed 3% at the farthest outlet to provide reasonable efficiency of operation.
Raceway Sealing for Temperature Differences (NEC 300.7(A)) NEC 300.7(A)
Where portions of a raceway are exposed to different temperatures and condensation is a problem, the raceway must be sealed to prevent circulation of warm air to the colder section.
Steel Plate Minimum Thickness for Cable Protection (NEC 300.4(A)(1)) NEC 300.4(A)(1)
When a cable or raceway cannot be installed with the required 1¼-in. edge distance from a wood member, a steel plate at least 1/16 in. (1.6 mm) thick must protect it from fastener penetration.
Adjustment Factor — More Than 3 Current-Carrying Conductors in Flexible Cord (NEC Table 400.5(A)(3)) NEC Table 400.5(A)(3)
When a flexible cord or cable contains 4–6 current-carrying conductors, an 80% adjustment factor must be applied to the standard ampacity values.
Formulas to Know
Continuous Load Conductor Ampacity
Minimum ampacity = (Noncontinuous load × 1.00) + (Continuous load × 1.25)Branch-Circuit Voltage Drop (3% guideline)
Voltage drop (V) = Circuit voltage × 0.03 → must not exceed 3% at farthest outletRange Neutral Conductor Minimum Ampacity
Neutral ampacity = Branch-circuit rating × 0.70 (min 10 AWG; applies to 3-wire range circuit)Feeder Tap Conductor Ampacity (≤10 ft rule)
Tap conductor ampacity ≥ combined calculated loads supplied AND ≥ rating of downstream overcurrent deviceFlexible Cord Ampacity Adjustment (4–6 current-carrying conductors)
Adjusted ampacity = Table ampacity × 0.80Bored Hole Edge Distance Check
Edge of hole ≥ 1.25 in. (32 mm) from nearest edge of wood member; if not, add ≥1/16 in. steel plate