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
Flexible Metal Conduit (FMC)vsLiquidtight Flexible Metal Conduit (LFMC)
FMC shall not be used in wet locations or underground, while LFMC is permitted where flexibility or protection from machine oils, liquids, vapors, or solids is required and is permitted for direct burial where listed and marked for the purpose.
NEC 2020 Section 350.10Series circuit total resistancevsParallel circuit total resistance
In a series circuit total resistance is the sum of all resistances, while in a parallel circuit total resistance is always LESS than the resistance of any individual branch.
Ugly's Electrical References, Series CircuitsEscalator and moving walk driving machine motorsvsElevator and dumbwaiter driving machine motors
Duty on escalator and moving walk driving machine motors is rated as continuous (620.61(B)(2)), while elevator and dumbwaiter driving machine motors are rated as intermittent (620.61(B)(1)).
NEC 2020 Section 620.61(B)(2)Straight pull box sizing (conductors 4 AWG or larger)vsAngle or U pull box sizing (conductors 4 AWG or larger)
Straight pulls require box length not less than 8 times the trade size of the largest raceway, while angle/U pulls require not less than 6 times the trade size of the largest raceway in a row plus the sum of the diameters of all other raceway entries on the same wall.
NEC 2020 Section 314.28(A)(1)Nontime-delay fuse for AC polyphase motorvsDual element (time-delay) fuse for AC polyphase motor
Table 430.52 permits nontime-delay fuses at a maximum of 300% of motor full-load current, while dual element (time-delay) fuses are limited to 175% of full-load current.
NEC 2020 Table 430.52Wye-start, delta-run motor conductors (controller to motor)vsPart-winding connected motor conductors (controller to motor)
Wye-start, delta-run conductors must be not less than 72% of motor full-load current (58% × 1.25), while part-winding connected motor conductors must be not less than 62.5% (50% × 1.25).
NEC 2020 Section 430.22(C)Cord sets/receptacles fixed in place and not exposed to damagevsAll other cord sets and receptacles
Under the assured equipment grounding conductor program, fixed cord sets and receptacles not exposed to damage are tested at intervals not exceeding 6 months, while other cord sets and receptacles must be tested at intervals not exceeding 3 months.
29 CFR 1926, Subpart K, §1926.404(b)(1)(iii)(E)(4)Plug fuses rated 15 amperes and lowervsPlug fuses of higher ampere rating
Plug fuses of 15-ampere and lower rating must be identified by a hexagonal configuration of the window, cap, or other prominent part to distinguish them from higher-rated fuses.
NEC 2020 Section 240.50(C)RMC support distance from terminationsvsFMC support distance from terminations
RMC shall be securely fastened within 900 mm (3 ft) of each box/termination (1.5 m/5 ft permitted only where structural members do not readily permit fastening within 3 ft), while FMC shall be fastened within 300 mm (12 in.) of each box, cabinet, conduit body, or other termination.
NEC 2020 Section 344.30(A)(1)Motor branch-circuit conductor ampacityvsMotor feeder conductor ampacity
Branch-circuit conductors for a single continuous-duty motor must be at least 125% of that motor's full-load current, while feeder conductors must be at least 125% of the highest-rated motor plus the sum of the full-load currents of the other motors.
NEC 2020 Section 430.22Grounded (neutral) conductor at a separate building/structurevsEquipment grounding conductor at a separate building/structure
Per 250.32(B)(1), the equipment grounding conductor is run with the supply conductors and connected to the building disconnecting means and grounding electrode(s), while any installed grounded conductor shall NOT be connected to the equipment grounding conductor or to the grounding electrode(s) at that structure.
NEC 2020 Section 250.32(B)(1)Externally OperablevsDead Front / Enclosed / Guarded
Externally operable means capable of being operated without exposing the operator to contact with live parts; dead front means without live parts exposed on the operating side, enclosed means surrounded by a case or housing to prevent accidental contact, and guarded means covered, shielded, or protected to remove the likelihood of approach to a point of danger.
NEC 2020 Article 100 (Definitions, Part I — Externally Operable)Key Terms
Continuous Load NEC 2020 Article 100
A load where the maximum current is expected to continue for 3 hours or more.
Externally Operable NEC 2020 Article 100 (Definitions, Part I — Externally Operable)
Capable of being operated without exposing the operator to contact with live parts.
Competent Person (OSHA) OSHA 1926 CFR 29, Page 31
One who is capable of identifying existing and predictable hazards in the surroundings or working conditions that are unsanitary, hazardous, or dangerous to employees, and who has authorization to take prompt corrective measures to eliminate them (no specific degree, years of experience, or certificate required).
Interrupting Rating NEC 2020 Section 110.9
Equipment intended to interrupt current at fault levels must have an interrupting rating at nominal circuit voltage at least equal to the current available at the line terminals of the equipment.
High-Impedance Grounded Neutral System NEC 2020 Section 250.36
A system in which a grounding impedance limits ground-fault current to a low value; permitted for 3-phase AC systems of 480 volts to 1000 volts when all specified conditions are met.
Supply-Side Bonding Jumper NEC 2020 Section 250.30(A)(2)
The jumper installed with the circuit conductors from a separately derived system's source enclosure to the first disconnecting means enclosure when they are in separate enclosures.
Main Bonding Jumper (screw type) NEC 2020 Section 250.28(B)
Where a main or system bonding jumper is a screw only, the screw must be identified with a green finish that is visible with the screw installed.
Effective Ground-Fault Current Path NEC 2020 Section 250.4(A)(5)
The intentionally constructed low-impedance path for fault current; the earth shall not be considered an effective ground-fault current path.
Objectionable Current NEC 2020 Section 250.6(B)
Current resulting from multiple grounding connections; where the requirements of 250.4(A)(5) or (B)(4) are still met, one permitted remedy is to discontinue one or more but not all of such grounding connections (never all of them).
Type S Flexible Cord NEC 2020 Table 400.4
A 600V hard service cord with thermoset insulation and thermoset outer covering, suitable for pendant or portable use in damp locations with an extra-hard-usage rating.
Pull Point NEC 2020 Section 358.26
A point such as a conduit body or box that terminates a run for bend-counting purposes; bends are limited to 360° between pull points, so each section between pull points may have up to 360° of bends.
Abandoned Class 2, Class 3, and PLTC Cable NEC 2020 Section 725.25
Cable whose accessible portion must be removed; cables identified for future use must carry a tag durable enough for the environment involved.
Supplemental Grounding Electrode NEC 2020 Section 250.53(A)(2)
An additional electrode of a type in 250.52(A)(2) through (A)(8) required to supplement a single rod, pipe, or plate electrode, unless that single electrode has a resistance to earth of 25 ohms or less.
Transformer Vault NEC 2020 Section 450.48
An enclosure for transformers in which materials shall not be stored — a blanket prohibition with no exception for noncombustible materials.
Emergency Action Plan (OSHA construction) OSHA 1926 CFR 29, §1926.35(e)(3), Page 33
A required plan that, for employers with 10 or fewer employees, may be communicated orally to employees with no written plan required.
Arc-Flash Label for Service Equipment Rated 1200 A or More (other than dwellings) NEC 2020 Section 110.16(B)
A permanent label that must state nominal system voltage, available fault current at the service overcurrent devices, the clearing time of those devices based on available fault current, and the date the label was applied — conductor sizes are not required.
Formulas to Know
Current from power and voltage (Ohm's Law / power formula)
I = P / E (e.g., 1800 W / 120 V = 15 A; 1200 W / 120 V = 10 A)Three-phase kilowatt load
KW = (E × I × PF × 1.73) / 1000 (e.g., (460 × 52 × 0.80 × 1.73)/1000 ≈ 33 KW)Total resistance in series and parallel circuits
Series: RT = R1 + R2 + R3 (20 + 25 + 15 = 60 ohms). Parallel: RT is always less than the smallest branch resistance.Service-entrance conductor minimum ampacity with continuous loads
Ampacity ≥ noncontinuous load + (1.25 × continuous load) (150 A + 1.25 × 80 A = 250 A)Motor conductor ampacity (branch circuit, feeder, and special connections)
Single continuous-duty motor branch circuit: 1.25 × FLC (1.25 × 65 A = 81.25 A). Feeder: (1.25 × largest motor FLC) + sum of other motor FLCs (1.25 × 65 + 40 = 121.25 A). Wye-start/delta-run controller-to-motor: ≥72% of FLC. Part-winding: ≥62.5% of FLC.Motor running overload device maximum trip setting
Service factor 1.15 or greater: ≤125% of nameplate FLC (28 A × 1.25 = 35 A; 14 A × 1.25 = 17.5 A); increases up to 140% may be permitted under 430.32(C) if 125% is insufficient.Motor branch-circuit short-circuit and ground-fault protection (fuse sizing)
Nontime-delay fuse: 300% × FLC (65 A × 3.00 = 195 A; 52 A × 3.00 = 156 A). Dual element/time-delay fuse: 175% × FLC (65 A × 1.75 = 113.75 A). If the result is not a standard size, the next higher standard size is permitted per 430.52(C)(1) Exc. 1 (195 A → 200 A).Pull/junction box minimum dimensions (conductors 4 AWG or larger)
Straight pull: length ≥ 8 × trade size of largest raceway. Angle/U pull: distance from raceway entry to opposite wall ≥ (6 × trade size of largest raceway in that row) + sum of diameters of all other raceway entries on the same wall ((6×2)+1 = 13 in.; (6×3)+2 = 20 in.; 6×3 = 18 in. with no other entries).Bending layout rules (EMT hand bending and MC cable radius)
90° stub-up: mark = stub height − take-up (12 in. − 6 in. take-up for ¾ in. EMT = 6 in.). Offset: distance between marks = multiplier × offset depth (1.4 × 5 in. = 7 in. for 45°). 3-point saddle: side marks = 2.5 × obstruction height each side of center (2.5 × 3 = 7½ in.), center bent 45° and sides 22½°, shrink = 3/16 × height. Type MC with interlocked armor or corrugated sheath: minimum bend radius = 7 × external diameter (7 × 1 in. = 7 in.).Percentage-of-rating limits (dwelling feeder, cord-and-plug equipment, room air conditioner)
Dwelling service/feeder 83% rule: 0.83 × 200 A = 166 A; with a 0.91 temperature correction factor the required table ampacity = 166 / 0.91 ≈ 182 A. Cord-and-plug utilization equipment not fastened in place on a circuit with other outlets: ≤80% of branch-circuit rating (0.80 × 20 A = 16 A). Cord-and-plug room air conditioner sharing a circuit with lighting/other outlets: total marked rating ≤50% of branch-circuit rating (0.50 × 20 A = 10 A).