Exam Cheat Sheet · Quick Reference
Mississippi Residential Electrician
Mississippi · 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
60
Passing score
70%
Exam time
180 min
Administered by
PSI Services Contractor
Format
Reference materials allowed
Mississippi State Portion 60 questions
General Electrical Knowledge
13 Q · 22%
GFCI protection requirements by location for dwelling and non-dwelling unitsAFCI protection requirements for dwelling unit branch circuitsBranch circuit conductor sizing and ampacity requirementsOvercurrent protection devices: fuses, circuit breakers, and standard ampere ratingsGrounding and bonding system requirements and electrode typesBranch circuit voltage limitations and ratingsMultiwire branch circuit requirements and disconnecting meansFeeder conductor sizing and overcurrent protection
Services, Feeders, and Branch Circuits
15 Q · 25%
Service conductor clearances and installation requirements (overhead and underground)Service disconnecting means location, rating, and maximum number of disconnectsService entrance conductor sizing, ampacity, and wiring methodsBranch circuit ratings, conductor sizing, and permissible loadsFeeder conductor sizing, overcurrent protection, and load calculationsBranch-circuit, feeder, and service load calculations including demand factorsGround-fault and arc-fault circuit interrupter protection requirementsService overcurrent protection and ground-fault protection of equipment
Overcurrent Protection
5 Q · 8%
Standard ampere ratings for fuses and inverse time circuit breakersProtection of conductors based on ampacity and wire sizeLocation requirements for overcurrent devices in dwellings and premisesFeeder and branch circuit tap conductor rules and length limitationsGround-fault protection of equipment requirementsCircuit breaker requirements, markings, and arc energy reductionSupplementary overcurrent protection and grounded conductor restrictionsOvercurrent protection for panelboards and service equipment
Grounding and Bonding
6 Q · 10%
Grounding electrode system types and installation requirementsGrounding electrode conductor sizing and installationEquipment grounding conductor types, sizing, and identificationMain bonding jumper and system bonding jumper requirementsBonding of piping systems, structural metal, and service equipmentEffective ground-fault current path requirementsGrounding of service-supplied and separately derived AC systemsMethods of connecting grounding and bonding conductors to electrodes
Conductors and Cables
5 Q · 8%
Conductor ampacity tables and temperature ratings (Table 310.16, 310.17, 310.18, 310.19)Ambient temperature correction factors and adjustment factors for more than three current-carrying conductorsConductor types, insulation designations, and permitted applications by location (dry, damp, wet, direct burial, sunlight exposure)Minimum conductor size, material requirements, and stranding rules (copper, aluminum, copper-clad aluminum)Conductor identification and marking requirements (grounded, ungrounded, equipment grounding conductors)Conductors in parallel requirements (size, length, material, insulation type, termination)Cable types and their permitted/prohibited uses (NM, NMC, MC, AC, MI, UF, USE, SE, TC)Single-phase dwelling service and feeder conductor sizing (Table 310.12)
Raceways and Boxes
4 Q · 7%
Conduit types, definitions, and permitted uses (EMT, IMC, RMC, FMC, LFMC, PVC, HDPE, ENT, LFNC, FMT)Securing and supporting requirements for raceways (fastening intervals and distances from terminations)Number of conductors and conduit fill calculations (Chapter 9 Table 1 percentage fill)Bends in conduit — how made and maximum number per run (four quarter bends limit)Outlet, device, pull, and junction box sizing, fill calculations, and installation requirementsBox and conduit body support methods (surface mounting, structural mounting, raceway-supported enclosures)Grounding requirements for metallic and nonmetallic raceways and boxesCorrosion protection for raceways, boxes, and fittings in wet, damp, and corrosive environments
Lighting
4 Q · 7%
Luminaire installation requirements by location (wet, damp, corrosive, bathtub/shower areas, clothes closets)Recessed luminaire clearance, insulation contact (Type IC vs. non-IC), and thermal protection requirementsLuminaire support methods (outlet boxes, suspended ceilings, poles, trees) and weight limitationsGrounding and bonding of luminaires and exposed conductive partsWiring of luminaires (conductor insulation, polarization, splices, pendant conductors, luminaires as raceways)Lighting track installation, connected load, prohibited locations, and groundingElectric-discharge and fluorescent luminaire special provisions (thermal protection, disconnecting means, ballast requirements)Low-voltage lighting systems (Article 411) and required lighting outlets in dwelling units (NEC 210.70)
Specialty
4 Q · 7%
GFCI protection requirements for pools, spas, hot tubs, and fountainsEquipotential bonding requirements for permanently installed pools and spasUnderwater luminaire installation and wiring (wet-niche, dry-niche, no-niche)Receptacle, lighting, and switching device location clearances from waterWiring methods and equipment grounding for pool motors and corrosive environmentsDisconnecting means and maintenance disconnect requirements for pool and spa equipmentFixed electric space-heating equipment installation, overcurrent protection, and disconnecting meansAir-conditioning and refrigerating equipment branch circuits, disconnecting means, and overcurrent protection
Safety
4 Q · 7%
Ground-fault circuit interrupter (GFCI) requirements and assured equipment grounding conductor programsLockout and tagging of circuits and deenergized equipmentPersonal protective equipment for electrical work (rubber insulating gloves, blankets, sleeves, and head protection)Working clearances and workspace requirements around electrical equipmentGrounding and bonding of electrical systems, equipment, and conductorsGuarding of live parts operating at 50 volts or moreTemporary wiring safety requirements on construction sitesFire protection and flammable liquid storage safety requirements on jobsites
Key Distinctions
Continuous LoadvsNoncontinuous Load
Feeder conductors must be sized at 125% of the continuous load but only 100% of the noncontinuous load, so the two portions are added differently when calculating required ampacity.
NEC, Section 215.2(A)(1)(a)Type 1 SPDvsType 2 SPD
Both Type 1 and Type 2 surge-protective devices satisfy the NEC requirement for dwelling-unit services, but either type must be installed; no other SPD type is listed as acceptable for this application.
NEC, Section 230.67(A) and (C)Overcurrent Device in Bathroom (dwelling)vsService Disconnect in Bathroom (dwelling)
Both are prohibited in bathrooms of dwelling units—overcurrent devices (other than supplementary) under NEC 240.24(E) and service disconnecting means under NEC 230.70(A)(2)—with no exceptions.
NEC, Section 230.70(A)(2)14 AWG Copper Max OCPDvs20-A Branch Circuit Max Single-Equipment Load
14 AWG copper is limited to a maximum 15-A overcurrent device, while a single cord-and-plug-connected appliance on a 20-A circuit is limited to 16 A (80% of 20 A).
NEC 2020, Section 240.4(D)(3)Underground Service-Entrance Conductors (min size)vsPool Equipotential Bonding Conductor (min size)
Underground service-entrance conductors must be at least 8 AWG copper or 6 AWG aluminum, while the solid copper bonding conductor for pool equipotential bonding must be at least 8 AWG solid copper.
NEC, Section 230.31(B)Hermetic Compressor Disconnect Rating (min)vsHermetic Compressor Overcurrent Protection (initial max)
The disconnecting means must be rated at least 115% of the motor-compressor rated-load current, whereas the branch-circuit overcurrent device is initially set at no more than 175% (expandable to 225% if needed for starting).
NEC Handbook, Section 440.12(A)(1)Fixed Electric Space-Heating Branch-Circuit ConductorsvsResistance Heating Element Overcurrent Protection
Branch-circuit conductors for fixed electric space heating must be sized at 125% of the load, while individual resistance heating elements must be protected at no more than 48 A per subdivided load (equipment-level protection limited to 60 A total).
NEC Handbook, Section 424.4(B)Pool Receptacle Minimum Distance (closest permitted)vsPool Receptacle GFCI Requirement Distance
A receptacle may be placed as close as 6 ft from the inside pool wall (minimum), but all 15- and 20-A, 125-V receptacles within 20 ft of the pool wall require GFCI protection.
NEC Handbook, Section 680.22(A)(1)Outdoor Pool Luminaire Height (above water)vsWet-Niche Luminaire Depth (below water)
Outdoor luminaires above or within 5 ft horizontally of a pool must be at least 12 ft above maximum water level, while wet-niche underwater luminaire tops must be at least 18 in. below normal water level.
NEC Handbook, Section 680.22(B)(1)83% Rule (one-family dwelling service conductors)vs125% Rule (feeder/branch-circuit conductors for continuous loads)
Service conductors for a 100–400 A one-family dwelling service may have ampacity as low as 83% of the service rating, whereas feeder and branch-circuit conductors supplying continuous loads must be sized at not less than 125% of the continuous load.
NEC, Section 310.12(A)AC/Refrigeration Equipment Disconnect Location (permitted)vsAC/Refrigeration Equipment Disconnect Location (prohibited)
The disconnect must be within sight from and readily accessible from the equipment, but it is expressly prohibited from being located on panels designed to allow access to the equipment or to obscure the nameplate.
NEC Handbook, Section 440.14Emergency Shutoff for Spa at One-Family DwellingvsEmergency Shutoff for Spa at Other Occupancies
A clearly labeled emergency shutoff switch located at least 5 ft from the spa is required for spas and hot tubs at locations other than one-family dwellings, but this requirement explicitly does not apply to one-family dwellings.
NEC Handbook, Section 680.41Key Terms
Feeder Conductor Ampacity (continuous + noncontinuous loads) NEC, Section 215.2(A)(1)(a)
Per NEC 215.2(A)(1)(a), feeder conductors must have ampacity not less than the noncontinuous load plus 125% of the continuous load.
Small-Appliance Branch Circuits (dwelling kitchen) NEC, Section 210.11(C)(1); IRC Section E3703.2
Per NEC 210.11(C)(1), a minimum of two 20-A branch circuits must be provided for receptacle outlets in the kitchen, dining room, pantry, breakfast area, and similar areas.
General Lighting Unit Load (dwelling) NEC, Section 220.14(J)
Per NEC 220.14(J), the minimum unit load for general lighting and general-use receptacles in dwelling units is 3 VA per square foot.
Service Disconnect—Prohibited Location (bathroom) NEC, Section 230.70(A)(2)
Per NEC 230.70(A)(2), service disconnecting means shall not be installed in bathrooms, with no exceptions.
Underground Service-Entrance Conductor Minimum Size NEC, Section 230.31(B)
Per NEC 230.31(B), underground service conductors shall be no smaller than 8 AWG copper or 6 AWG aluminum or copper-clad aluminum.
Surge-Protective Device (SPD) Requirement for Dwelling Services NEC, Section 230.67(A) and (C)
Per NEC 230.67(A) and (C), all services supplying dwelling units shall be provided with a Type 1 or Type 2 SPD.
83% Rule for One-Family Dwelling Service Conductors NEC, Section 310.12(A)
Per NEC 310.12(A), service conductors rated 100–400 A supplying the entire load of a one-family dwelling are permitted to have an ampacity not less than 83% of the service rating.
Demand Factor—General Lighting Load (dwelling, above 3,000 VA) NEC, Informative Annex D, Example D1(a)
Per NEC Table 220.42 (illustrated in Annex D Example D1(a)), the portion of the combined general lighting and small-appliance load exceeding 3,000 VA is taken at a 35% demand factor.
Adjustment Factor Exemption (short raceway ≤ 24 in.) NEC, Section 310.15(C)(1)(b)
Per NEC 310.15(C)(1)(b), conductor ampacity adjustment factors for more than three current-carrying conductors do not apply when the raceway length does not exceed 24 in. (600 mm).
Overcurrent Device—Prohibited Location in Dwelling Bathroom NEC 2020, Section 240.24(E)
Per NEC 240.24(E), overcurrent devices other than supplementary overcurrent protection shall not be located in bathrooms of dwelling units, dormitory units, or guest rooms.
Pool Equipotential Bonding Perimeter NEC Handbook, Section 680.26(B)(2)
Per NEC 680.26(B)(2), the perimeter surface to be bonded extends 1 m (3 ft) horizontally beyond the inside walls of the pool, including unpaved surfaces and other paving types.
Pool Wiring—Minimum Equipment Grounding Conductor Size NEC Handbook, Section 680.21(A)(1)
Per NEC 680.21(A)(1), wiring methods in corrosive pool environments shall contain an insulated copper equipment grounding conductor sized per Table 250.122 but not smaller than 12 AWG.
Fixed Electric Space-Heating Disconnect (one-family dwelling) NEC Handbook, Section 424.19(C)(3)
Per NEC 424.19(C)(3), in a one-family dwelling the service disconnecting means is permitted to serve as the other disconnecting means for fixed electric space-heating equipment when a unit switch with a marked 'off' position is used.
Corrosion-Resistant Wiring Methods (pool areas) NEC Handbook, Section 680.14
Per NEC 680.14, rigid metal conduit, intermediate metal conduit, rigid PVC conduit, and reinforced thermosetting resin conduit are recognized as resistant to the corrosive environment around pools; aluminum conduit is not permitted.
Household Range Minimum Branch-Circuit Rating NEC, Section 210.19(A)(3)
Per NEC 210.19(A)(3), ranges rated 8¾ kW or more require a minimum branch-circuit rating of 40 amperes.
Formulas to Know
Feeder/Branch-Circuit Conductor Ampacity (continuous loads)
Required ampacity ≥ Noncontinuous load (A) + 1.25 × Continuous load (A)General Lighting Load for Dwelling (VA)
Lighting load (VA) = Floor area (sq ft) × 3 VA/sq ftDemand Factor Application—Dwelling Lighting Load
Total demand = First 3,000 VA × 100% + Remaining VA × 35%83% Rule—One-Family Dwelling Service Conductor Minimum Ampacity
Min conductor ampacity = Service rating (A) × 0.83Temperature Correction—Required Table Ampacity
Required table ampacity = Required ampacity ÷ Correction factorMax Single Cord-and-Plug Load on Branch Circuit (80% rule)
Max equipment ampere rating = Branch-circuit rating (A) × 0.80Fixed Space-Heating Branch-Circuit Conductor Sizing
Min conductor ampacity = Total heating load (A) × 1.25Hermetic Compressor Disconnect Minimum Rating
Min disconnect rating = max(Rated-load current, Branch-circuit selection current) × 1.15Hermetic Compressor Branch-Circuit Overcurrent Protection (initial)
Max OCPD = max(Rated-load current, Branch-circuit selection current) × 1.75Rounding Rule for Load Calculations
Round to nearest whole ampere; drop decimal fractions < 0.5