Exam Cheat Sheet · Quick Reference
Mississippi Master 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
80
Passing score
70%
Exam time
180 min
Administered by
PSI Services Contractor
Format
Reference materials allowed
Mississippi State Portion 80 questions
General Electrical Knowledge
6 Q · 8%
NEC Article 100 definitions and terminologyEquipment examination, approval, and listing requirements (NEC 110.3)Electrical connections, conductor materials, and temperature limitations (NEC 110.14)OSHA 29 CFR 1926 Subpart V qualified employee training requirementsMinimum approach distances for energized lines and equipmentPersonal protective equipment for electrical work including arc-flash protectionGrounding and bonding definitions and conceptsCircuit types, overcurrent protection, and interrupting ratings (NEC 110.9-110.10)
Service, Feeders, and Branch Circuits
10 Q · 12%
Branch circuit ratings, conductor ampacity, and minimum wire size requirementsGFCI protection requirements by location for dwelling and non-dwelling occupanciesAFCI protection requirements for dwelling units and specific occupanciesService entrance conductor sizing, ampacity, and wiring methodsService disconnecting means requirements, ratings, and locationFeeder conductor sizing, overcurrent protection, and common neutral rulesBranch-circuit, feeder, and service load calculations including demand factorsMultiwire branch circuit requirements and conductor identification
Grounding and Bonding
7 Q · 9%
Grounding electrode system types and installation requirementsEquipment grounding conductor types, sizing, and identificationBonding requirements for services, piping systems, and structural metalMain bonding jumper and system bonding jumper sizing and installationGrounding electrode conductor sizing and installationAC system grounding requirements by voltage levelSeparately derived system grounding and bondingEffective ground-fault current path requirements
Conductors and Cables
10 Q · 12%
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 insulation types, designations, and application provisions (THHN, THWN, RHW, XHHW, etc.)Minimum conductor sizes and conductor material requirements (copper, aluminum, copper-clad aluminum)Conductors in parallel — requirements and restrictionsConductor identification — grounded, equipment grounding, and ungrounded conductorsConductor and cable marking requirementsUses permitted by location — dry, damp, wet, direct burial, sunlight exposure, corrosive conditions
Raceways and Boxes
7 Q · 9%
Box fill calculations and conductor volume allowances (Article 314.16)Pull and junction box minimum sizing for straight pulls and angle/U pulls (Article 314.28)Support and securing methods for boxes and conduit bodies (Article 314.23)Conduit types, uses permitted and not permitted (RMC, IMC, EMT, FMC, LFMC, PVC, ENT)Securing and supporting intervals for conduit raceway systemsConductor entry requirements and protection from abrasion at boxes and conduit bodies (Article 314.17)Box installation requirements: damp/wet locations, depth, flush mounting, and covers (Articles 314.15, 314.20, 314.24, 314.25)Cabinet and cutout box spacing, wiring gutters, and wire-bending space requirements (Articles 312.6, 312.11)
Special Occupancies and Equipment
7 Q · 9%
Hazardous location classification systems (Class/Division vs. Zone methodology) for commercial garages, spray application, and health care facilitiesWiring methods and equipment requirements for Zone 20, 21, and 22 locations with combustible dusts or ignitible fibers/flyingsHealth care facility essential electrical systems (Type 1 and Type 2 EES — life safety, critical, and equipment branches)Patient care space wiring, grounding, and receptacle requirements (Categories 1–4)Spray application, dipping, coating, and printing process area classification and electrical equipment requirementsCommercial garage (Article 511) area classification, wiring above and below Class I locations, and special equipmentAnesthetizing location classification and isolated power system requirementsMotion picture projection room wiring, conductor sizing, and equipment requirements (Article 540)
Electrical Power
6 Q · 8%
Minimum approach distances for energized lines and equipment (AC and DC systems)Deenergizing lines and equipment for employee protection (lockout/tagout procedures)Protective grounding requirements and equipotential zonesPersonal protective equipment for electrical work (arc flash, flame-resistant clothing, fall protection)Training requirements for qualified employees working on or near energized partsWorking on or near exposed energized parts (live-line work practices)Enclosed spaces and underground electrical installations entry proceduresJob briefing requirements and information transfer between host and contract employers
Motors
6 Q · 8%
Branch-circuit conductor ampacity requirements (125% rule for single motors)Motor branch-circuit short-circuit and ground-fault protective device ratings (Table 430.52)Motor overload protection requirements and trip current percentages (430.32)Disconnecting means type, location, and ampere rating requirementsFull-load current values from NEC Tables 430.247–430.250Multiple motor feeder conductor sizing and overcurrent protection (430.24, 430.62)Motor controller ratings and requirements (horsepower rating, design requirements)Special motor wiring configurations (multispeed, wye-start/delta-run, part-winding, adjustable-speed drives)
Low Voltage
2 Q · 2%
Article 720 conductor and equipment requirements for circuits under 50 voltsArticle 411 low-voltage lighting system components and listing requirementsArticle 411 secondary circuit isolation, grounding, and bare conductor installationClass 2 and Class 3 power source requirements and circuit classificationsClass 2 and Class 3 cable types, substitution hierarchy, and installation locationsSeparation of Class 2 and Class 3 circuits from power and Class 1 conductorsArticle 393 low-voltage suspended ceiling power distribution system installation and listingArticle 727 Type ITC instrumentation tray cable uses, ampacity, and overcurrent protection
Lighting
3 Q · 4%
Luminaire installation requirements by location (wet, damp, corrosive, bathtub/shower areas)Luminaires in clothes closets — permitted types and minimum clearancesSupport and mounting of luminaires (outlet boxes, suspended ceilings, poles, trees)Grounding of luminaires and lighting equipmentRecessed luminaire requirements — thermal protection, clearances, and insulation contact (Type IC vs. non-Type IC)Lighting track installation, connected load limits, and prohibited locationsElectric-discharge lighting systems — thermal protection, disconnecting means, and open-circuit voltage requirementsLow-voltage lighting systems (Article 411) — listing, secondary circuit requirements, and branch circuit ratings
Illuminated Signs
2 Q · 2%
Neon secondary-circuit wiring methods and installation requirements over 1000 voltsTransformer and electronic power supply ratings and secondary-circuit current limitsClass 2 power source listing, grounding, and secondary wiring requirementsElectrode connections, enclosures, and support requirements for neon tubingNeon tubing design, support, spacing, and physical damage protectionPhotovoltaic-powered sign wiring, equipment listing, and disconnecting meansRetrofit kit listing, installation, and marking requirementsSecondary conductor length limits, splicing, and insulation requirements for neon circuits
Fire Detection and Alarm Systems
3 Q · 4%
Fire alarm system requirements on construction sites (OSHA 29 CFR 1926.150)Alarm code posting and emergency notification proceduresClass 1 non-power-limited fire alarm circuit wiring methods and installationSeparation of fire alarm circuit conductors from power and Class 2/3 circuitsFire alarm cable types and listing requirements for different building locations (plenum, riser, general-purpose)Circuit integrity (CI) cables and fire-resistive cable systems for critical alarm circuitsUnderground and overhead fire alarm circuit conductor separation requirements
Safety Information
5 Q · 6%
Employer and contractor safety responsibilities under OSHA 29 CFR 1926Prime contractor and subcontractor joint safety responsibilityAccident prevention programs and competent person requirementsPersonal protective equipment (PPE) requirements and compliance dutiesSafety training and employee hazard recognition requirementsEmergency action plans and means of egressFirst aid procedures and medical services on the jobsiteElectrical safety definitions, lockout/tagout, and shock protection boundaries
Overcurrent Protection
6 Q · 8%
Plug fuses, fuseholders, and adapters (ratings, markings, and configurations)Type S fuses and Edison-base fuse requirements and interchangeabilityCartridge fuses classifications, markings, and fuseholder requirementsCircuit breaker markings, ratings, and operating requirementsArc energy reduction requirements for fuses and circuit breakers rated 1200A or higherOvercurrent device enclosures, mounting positions, and environmental requirementsDisconnecting means for fuses and guarding of arcing partsSeries ratings and reconditioned equipment restrictions
Key Distinctions
Continuous loadvsNoncontinuous load
A continuous load is one where the maximum current is expected to continue for 3 hours or more and must be taken at 125 percent when sizing service-entrance/feeder conductors, while noncontinuous load is counted at 100 percent.
NEC 2020 Article 100NEC Chapter 8 (Communications Systems)vsNEC Chapters 1 through 7
Chapter 8 is NOT subject to the requirements of Chapters 1 through 7 except where those requirements are specifically referenced in Chapter 8.
NEC 2020 Section 90.3Informational notes / explanatory materialvsCode requirements
Informational notes are included for informational purposes only and are not enforceable as requirements, unlike the mandatory Code text.
NEC 2020 Section 90.5(C)Series 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 single branch.
Ugly's Electrical References, Series CircuitsOptional dwelling calculation, 220.82(B)vsExisting dwelling additional-load calculation, 220.83(A)
220.82(B) takes 100 percent of the first 10 kVA plus 40 percent of the remainder, while 220.83(A) (no additional A/C or electric space heating being added) takes 100 percent of the first 8 kVA plus 40 percent of the remainder.
NEC 2020 Section 220.82(B)225.39(B) two-circuit feeder disconnect (30 A minimum)vs225.39(C) one-family dwelling feeder disconnect (100 A, 3-wire minimum)
Installations of not more than two 2-wire branch circuits need a disconnect rated at least 30 amperes, whereas a one-family dwelling supplied by a feeder needs at least 100 amperes, 3-wire.
NEC 2020 Section 225.39(B)225.39(C) one-family dwelling disconnect (100 A)vs225.39(D) all other installations (60 A)
The 100-ampere minimum applies specifically to the one-family dwelling's feeder disconnect; a separate structure such as a detached garage supplied by a feeder falls under the 'all others' category at not less than 60 amperes.
NEC 2020 Section 225.39(C)Nontime-delay fuse for motor branch-circuit protectionvsDual-element (time-delay) fuse
Per Table 430.52 for AC polyphase motors other than wound-rotor, nontime-delay fuses are limited to 300 percent of full-load current while dual-element time-delay fuses are limited to 175 percent.
NEC 2020 Table 430.52, NEC 430.52(C)(1), NEC 240.6(A)Wye-start, delta-run motor conductors (72%)vsPart-winding connected motor conductors (62.5%)
Conductors between controller and motor must be at least 72 percent of motor FLC for wye-start/delta-run (58% × 1.25) and at least 62.5 percent for part-winding connection (50% × 1.25).
NEC 2020 Section 430.22(C)Motor branch-circuit conductor ampacityvsMotor feeder conductor ampacity
A single continuous-duty motor branch circuit requires 125 percent of that motor's FLC, while a feeder requires 125 percent of the highest-rated motor plus the sum of the full-load currents of the other motors.
NEC 2020 Section 430.22GFCI protection in a dwelling kitchenvsAFCI protection in a dwelling kitchen
GFCI is required for receptacles serving countertop surfaces (210.8(A)(6)), while AFCI is required for all 120-volt, single-phase, 15- and 20-ampere branch circuits supplying outlets in dwelling unit kitchens (210.12(A)); countertop receptacles need both.
NEC 2020 Section 210.8(A)(6)Commercial kitchen equipment demand factor for 4 units (80%)vsDemand factor for 6 or more units (65%)
Table 220.56 (thermostatically controlled or intermittent-use kitchen equipment, other than dwelling units) allows 80 percent for 4 units and 65 percent for 6 or more units.
NEC 2020 Table 220.56Angle pull box sizing with other raceways on the same wallvsAngle pull box sizing with no other raceways on that wall
The minimum distance to the opposite wall is six times the trade size of the largest raceway plus the sum of the diameters of all other raceway entries on the same wall; with no other entries it is simply six times the largest trade size.
NEC 2020 Section 314.28(A)(2)Equipment terminations not listed/marked for higher temperaturevsEquipment listed and identified for higher-rated conductors
For circuits rated over 100 amperes (or marked for conductors larger than 1 AWG), terminations may be used only with conductors rated 75°C (167°F) unless the equipment is listed and identified for use with higher-rated conductors.
NEC 2020 Section 110.14(C)(1)(b)Key Terms
Continuous load NEC 2020 Article 100
A load where the maximum current is expected to continue for 3 hours or more; critical for sizing conductors and overcurrent devices.
Externally operable NEC 2020 Article 100 (Definitions, Part I — Externally Operable)
Capable of being operated without exposing the operator to contact with live parts (contrast: 'dead front' = no live parts exposed on the operating side; 'enclosed' = surrounded by a case or housing to prevent accidental contact; 'guarded' = covered, shielded or otherwise protected to remove the likelihood of approach to a point of danger).
Interrupting rating (110.9) 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-leg marking (110.15) NEC 2020 Section 110.15
On a 4-wire delta-connected system with the midpoint of one phase winding grounded, the conductor or busbar with the higher phase voltage to ground must be durably and permanently marked orange or by other effective means.
Arc-flash label for service equipment (110.16(B)) NEC 2020 Section 110.16(B)
For service equipment rated 1200 amps or more in other than dwelling units, a permanent label must show nominal system voltage, available fault current at the service overcurrent devices, clearing time of those devices based on available fault current, and the date the label was applied — conductor sizes are not required.
Small-appliance branch circuits (210.11(C)(1)) NEC 2020 Section 210.11(C)(1)
Two or more 20-ampere branch circuits that must be provided for all receptacle outlets specified in 210.52(B), including dwelling kitchen countertop receptacles, which may not be served by 15-ampere general-purpose circuits.
Multiwire branch circuit disconnect (210.4(B)) NEC 2020 Section 210.4(B)
Each multiwire branch circuit must be provided with a means that simultaneously disconnects all ungrounded conductors at the point where the branch circuit originates.
Plug fuse identification (240.50(C)) NEC 2020 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.
High-impedance grounded neutral system (250.36) 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 (250.30(A)(2)) NEC 2020 Section 250.30(A)(2)
For a grounded separately derived system whose source and first disconnecting means are in separate enclosures, a supply-side bonding jumper must be installed with the circuit conductors from the source enclosure to the first disconnecting means enclosure.
Main bonding jumper screw identification (250.28(B)) 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 visible with the screw installed.
Objectionable current (250.6(B)) NEC 2020 Section 250.6(B)
Current resulting from multiple grounding connections; where 250.4(A)(5) or (B)(4) is still satisfied, one permitted remedy is to discontinue one or more but not all of the grounding connections (never all of them).
Effective ground-fault current path (250.4(A)(5)) NEC 2020 Section 250.4(A)(5)
The intentional path for fault current; the Code states the earth shall not be considered an effective ground-fault current path.
Grounding at a separate structure (250.32(A)) NEC 2020 Section 250.32(A)
A building or structure supplied by a feeder or branch circuit must have a grounding electrode system and grounding electrode conductor per Part III of Article 250; where no electrode exists, the electrode(s) required by 250.50 must be installed.
Zone 20 location (506.5(B)(1)) NEC 2020 Section 506.5(B)(1)
A location in which ignitible concentrations of combustible dust or ignitible fibers/flyings are present continuously or for long periods of time.
Abandoned Class 2, Class 3, and PLTC cable (725.25) NEC 2020 Section 725.25
The accessible portion of abandoned Class 2, Class 3, and PLTC cables must be removed; cables identified for future use must be tagged with a tag durable enough for the environment.
Pull point (358.26) NEC 2020 Section 358.26
A point such as a conduit body or box that limits bends; EMT is limited to 360 degrees of bends between pull points, so each section between pull points may have up to 360 degrees.
Competent person (OSHA 29 CFR 1926.32(f)) OSHA 1926 CFR 29, Page 31
One 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 degree, years of experience, or certificate 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)Service-entrance / feeder conductor minimum ampacity with continuous loads
Minimum ampacity = noncontinuous load + (125% × continuous load) (e.g., 150 + (80 × 1.25) = 250 A; (100 × 1.25) + 30 = 155 A)Motor branch-circuit conductor ampacity (single continuous-duty motor)
Minimum ampacity = 125% × motor FLC from the motor tables (e.g., 125% × 65 A = 81.25 A)Motor feeder conductor ampacity (two or more motors)
Minimum ampacity = (125% × largest motor FLC) + sum of FLCs of the other motors (e.g., (1.25 × 65) + 40 = 121.25 A; (1.25 × 15.2) + 15.2 + 15.2 = 49.4 A)Motor overload device maximum trip (service factor 1.15 or greater)
Max trip = 125% × nameplate FLC (e.g., 28 × 1.25 = 35 A; 14 × 1.25 = 17.5 A); if insufficient, 430.32(C) permits incremental increases up to 140%Motor branch-circuit short-circuit/ground-fault fuse maximum (AC polyphase, other than wound-rotor)
Nontime-delay fuse = 300% × FLC; dual-element time-delay fuse = 175% × FLC; where the value is not a standard size, 430.52(C)(1) Ex. 1 permits the next higher standard size per 240.6(A) (e.g., 65 A × 300% = 195 A → 200 A; 65 A × 175% = 113.75 A; 52 A × 300% = 156 A)Junction/pull box minimum dimension for an angle pull (314.28(A)(2))
Distance from raceway entry to opposite wall = (6 × trade size of largest raceway) + sum of diameters of all other raceway entries on the same wall (e.g., (6×2)+1 = 13 in.; (6×3)+2 = 20 in.; (6×3) alone = 18 in.)One-family dwelling service conductor ampacity allowance (310.12(A))
For a 100–400 A service supplying the entire load of a one-family dwelling on a single-phase 120/240-volt system, conductors are permitted at 83% of the service rating (200 × 0.83 = 166 A)Generator conductor ampacity (445.13)
Conductors from the generator terminals to the first overcurrent device must be at least 115% × generator nameplate current (80 A × 1.15 = 92 A minimum)