Exam Cheat Sheet · Quick Reference

Idaho - ID JOURNEYMAN ELECTRICIAN EXAM

Idaho  ·  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
75
Exam time
270 min
Administered by
PSI Services Contractor
Format
Reference materials allowed

Idaho State Portion 100 questions

General Electrical Knowledge 13 Q · 13%
Wiring and Protection 25 Q · 25%
Wiring Methods and Materials 19 Q · 19%
Equipment for General Use 19 Q · 19%
Special Occupancies 12 Q · 12%
Special Equipment 6 Q · 6%
Special Conditions 6 Q · 6%

Key Distinctions

Mandatory NEC RulesvsPermissive NEC Rules

Mandatory rules use 'shall' or 'shall not' (required or prohibited actions), while permissive rules use 'shall be permitted' or 'shall not be required'.

Article 90.5(A)
Series Circuit CurrentvsSeries Circuit Resistance

In a series circuit, current is equal in all parts (IT = I1 = I2 = I3), while total resistance is the sum of all individual resistances (RT = R1 + R2 + R3).

Series Circuits
NEC Chapters 1–7vsNEC Chapter 8 (Communications Systems)

Chapters 1–7 apply generally to all covered installations, while Chapter 8 is independent and not subject to Chapters 1–7 except where specifically referenced therein.

NEC 90.3
Direct Burial Cable (underground cover)vsRigid Metal Conduit / IMC (underground cover)

Direct burial cables require a minimum cover of 600 mm (24 in.) in general locations, while rigid metal conduit or IMC requires only 150 mm (6 in.).

NEC Table 300.5(A)
Bored Hole Protection (wood members)vsNotched Wood Member Protection

Bored holes must keep the edge at least 32 mm (1-1/4 in.) from the wood edge or a steel plate is required, while cables in notches must always be covered by a steel plate at least 1.6 mm (1/16 in.) thick.

NEC 300.4(A)(1)
120/240 V Single-Phase Neutral Conductor Colorvs120/240 V Single-Phase Ungrounded Conductor Colors

The grounded neutral conductor is white or gray, while the two ungrounded conductors are black (L1) and red (L2).

Ugly's Electrical References, Common Electrical Distribution Systems
120/208 V Three-Phase Wye (C phase color)vs120/240 V Delta High-Leg (B phase color)

In a 120/208 V three-phase four-wire wye system the C phase is blue, while in a 120/240 V delta high-leg system the B phase (high leg) is orange.

Ugly's Electrical References, Common Electrical Distribution Systems
NEC PurposevsNEC Design Specification

The NEC's purpose is the practical safeguarding of persons and property from electrical hazards; it is explicitly NOT intended as a design specification or instruction manual for untrained persons.

Article 90.2(A)
Vertically Operated Switch Handle – Up PositionvsVertically Operated Switch Handle – Down Position

Per NEC 404.7, the up position of a vertically operated switch handle is the closed (on) position, implying the down position is the open (off) position.

NEC 404.7
Elevator Raceway Fill (Article 620)vsGeneral Wiring Raceway Fill (Chapter 9)

Elevator installations allow a maximum of 50% raceway fill per Article 620.33, which differs from the standard fill percentages in Chapter 9, Table 1 used for general wiring.

Article 620.33
Ohm's Law (I = E ÷ R)vsPower Formula / Watt's Law (I = P ÷ E)

Ohm's Law calculates current from voltage and resistance (I = E ÷ R), while Watt's Law calculates current from power and voltage (I = P ÷ E); both appear on the Ohm's Law wheel but are technically distinct formulas.

Ugly's Electrical References, Ohm's Law
Continuous Load Feeder Sizing (125%)vsAmpacity Adjustment for 7–9 Conductors (70%)

Feeder conductors must be sized at 125% of continuous loads per NEC 215.2(A)(1), while conductors in a raceway containing 7–9 current-carrying conductors must have their ampacity derated to 70% per NEC Table 310.15(C)(1).

NEC 215.2(A)(1)

Key Terms

NEC Purpose (Article 90.1(A)) Article 90.2(A)
Per NEC 90.1(A), the Code exists for the practical safeguarding of persons and property from hazards arising from the use of electricity, and is not a design specification.
Authority Having Jurisdiction (AHJ) – Article 90.4 Article 90.4(B)
Per NEC Article 90.4, the AHJ is responsible for making interpretations of NEC rules, approving equipment and materials, and granting special permissions contemplated by the Code.
Mandatory Rule – Article 90.5(A) Article 90.5(A)
Per NEC 90.5(A), a mandatory rule requires or prohibits a specific action and is identified by the terms 'shall' or 'shall not'.
Permissive Rule – Article 90.5(B) NEC 90.5(A) and 90.5(B)
Per NEC 90.5(B), a permissive rule identifies actions that are allowed but not required, and is identified by the terms 'shall be permitted' or 'shall not be required'.
NEC Chapter 8 Independence – NEC 90.3 NEC 90.3
Per NEC 90.3, Chapter 8 (Communications Systems) is not subject to the requirements of Chapters 1 through 7 except where those requirements are specifically referenced in Chapter 8.
SI vs. Inch-Pound Compliance – Article 90.9(D) Article 90.9(D)
Per Article 90.9(D), compliance with numbers shown in either the SI (metric) system or the inch-pound system constitutes compliance with the NEC.
Vertically Operated Switch Handle – NEC 404.7 NEC 404.7
Per NEC 404.7, where switch or circuit breaker handles are operated vertically, the up position shall be the closed (on) position.
Elevator Raceway Fill – Article 620.33 Article 620.33
Per NEC Article 620.33, the sum of the cross-sectional area of individual conductors in elevator raceways shall not exceed 50% of the interior cross-sectional area of the raceway.
Minimum Cover – Underground Direct Burial (NEC Table 300.5(A)) NEC Table 300.5(A)
Per NEC Table 300.5(A), direct-buried cables in general locations require a minimum cover of 600 mm (24 in.), while rigid metal conduit or IMC requires only 150 mm (6 in.).
Steel Plate Protection – NEC 300.4(A)(2) NEC 300.4(A)(2)
Per NEC 300.4(A)(2), cables or raceways in notches in wood members must be protected by a steel plate at least 1.6 mm (1/16 in.) thick to prevent nail or screw penetration.
Minimum Service Rating – One-Family Dwelling (NEC 230.79(C)) NEC 230.79(C)
Per NEC 230.79(C), the service disconnecting means for a one-family dwelling shall have a rating of not less than 100 amperes, 3-wire.
Overhead Service Clearance over Public Streets – NEC 230.24(B) NEC 230.24(B)
Per NEC 230.24(B), overhead service conductors not exceeding 1000 V nominal must maintain a minimum clearance of 5.5 m (18 ft) over public streets and alleys.
Ampacity Derating – 7–9 Conductors (NEC Table 310.15(C)(1)) NEC Table 310.15(C)(1)
Per NEC Table 310.15(C)(1), when 7–9 current-carrying conductors are installed in a raceway or cable, the ampacity adjustment factor is 70%.
Minimum Copper Conductor Size – NEC 310.3(A) NEC 310.3(A)
Per NEC 310.3(A), the minimum conductor size for general wiring rated up to 2000 volts is 14 AWG copper or 12 AWG aluminum/copper-clad aluminum.
Ferrous Metal Enclosure Grouping – NEC 300.20(A) NEC 300.20(A)
Per NEC 300.20(A), AC conductors in ferrous metal enclosures must have all phase conductors, grounded conductors, and equipment grounding conductors grouped together to prevent inductive heating.
High-Leg (B Phase) Voltage Ugly's Electrical References, Common Electrical Distribution Systems
In a 120/240 V three-phase four-wire delta high-leg system, the B phase (orange conductor) measures 208 volts to the grounded neutral conductor.

Formulas to Know

Ohm's Law – CurrentI = E ÷ R
Ohm's Law – VoltageE = I × R
Ohm's Law – ResistanceR = E ÷ I
Power Formula (Watt's Law) – PowerP = E × I
Power Formula – Current from Watts and VoltsI = P ÷ E
Series Circuit – Total ResistanceRT = R1 + R2 + R3 + ...
Series Circuit – Current EqualityIT = I1 = I2 = I3
Continuous Load Feeder Minimum AmpacityMinimum Ampacity = Noncontinuous Load + (1.25 × Continuous Load)
Ampacity Derating – Multiple Conductors in RacewayDerated Ampacity = Table Ampacity × Adjustment Factor (e.g., 0.70 for 7–9 conductors)
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