Your FREE Journeyman Electrician Flashcards 2026 – 200+ Cards

E = I × R. Voltage (volts) equals current (amperes) times resistance (ohms). Rearranged: I = E ÷ R and R = E ÷ I.

P = E × I (watts). Also P = I² × R and P = E² ÷ R using Ohm's law.

P = E × I × PF, where PF is the power factor.

P = 1.732 × E × I × PF (the 1.732 is √3). Memorize 1.732.

Electrical pressure (potential difference), measured in volts (E or V) — what pushes current through a circuit.

The flow of electric charge, measured in amperes (I or A). Same everywhere in a series circuit.

Opposition to current flow, measured in ohms (Ω). Adds in series; combines reciprocally in parallel.

Current is the same through every component (one path).

Resistances add: R = R₁ + R₂ + R₃.

Voltage divides across the resistors (the drops add up to the source).

Voltage is the same across every branch.

1/R = 1/R₁ + 1/R₂ + 1/R₃. Total is less than the smallest branch.

Half the value of one (e.g., two 20 Ω in parallel = 10 Ω).

So each load gets full voltage and one failure doesn't kill the rest.

Series: everything stops. Parallel: only that one branch stops.

Ratio of real power (watts) to apparent power (volt-amperes). 1.0 (unity) = all power does useful work.

Watts = real power (actual work). VA = apparent power. Power factor is the ratio between them.

Single-phase: one alternating voltage (120/240 V dwellings). Three-phase: three voltages 120° apart, for larger loads.

120 V (lighting/receptacles) and 240 V (large appliances), from a 120/240 V single-phase service.

Voltage lost along a conductor due to its resistance. Grows with longer runs, smaller wire, and more current.

≤3% on a branch circuit or feeder, ≤5% total. These are Informational Notes (recommendations), not enforceable rules.

VD = (2 × K × I × L) ÷ CM. K ≈ 12.9 (copper), 21.2 (aluminum); L = one-way length (ft); CM = circular mils.

VD = (1.732 × K × I × L) ÷ CM. Replace the 2 in the single-phase formula with 1.732.

Upsize the conductor (more circular mils = lower resistance = less drop).

Dims lights, slows and overheats motors, and wastes energy as heat in the conductor.

About 12.9 ohm-cmil/ft for copper (21.2 for aluminum).

The National Electrical Code (NFPA 70) — the model safety code, updated every 3 years, that journeyman exams are based on.

The 2023 NEC (NFPA 70-2023). States adopt on a lag — many are still on the 2020 or 2017 edition.

A three-way switch — used in pairs to control one load from two locations.

A four-way switch — used between two three-way switches to control a load from three or more locations.

A unit of energy: 1,000 watts used for one hour. It's what the utility meter measures and bills.

AC (alternating current) reverses direction periodically (utility power, 60 Hz in the U.S.). DC (direct current) flows one way (batteries, electronics).

60 hertz (Hz) — the AC voltage completes 60 cycles per second.

Total opposition to AC current (resistance + reactance), measured in ohms. The AC counterpart of resistance.

Larger conductor (lower AWG number, more circular mils) = lower resistance = less voltage drop and heating.

Current into a junction equals current out of it — the basis for analyzing parallel branches.

Longer run = more resistance = more voltage drop (drop is proportional to length).

Apparent (VA) is the total; real (W) does useful work; reactive (VAR) is stored/returned by inductors and capacitors.

1 horsepower ≈ 746 watts. Motor nameplate HP × 746 ÷ (efficiency × PF) estimates input watts.

Calculations and code lookup. The exam is largely code-based and (in most states) open-book — speed at finding articles/tables matters.

I = P ÷ E = 1,200 ÷ 120 = 10 amperes.

R = E ÷ I = 240 ÷ 12 = 20 ohms.

I = P ÷ (1.732 × E) = 50,000 ÷ (1.732 × 480) ≈ 60 amperes.

By Ohm's law I = E ÷ R, current is directly proportional to voltage when resistance is constant.

The conductors and equipment that deliver electricity from the utility to a building's wiring (Article 230).

100 amperes, three-wire.

At least equal to the calculated load they supply.

120/240 V single-phase dwelling services and main feeders may be sized at 83% of the rating (dwelling services/feeders table, 310.12).

The conductors from the service point/meter to the service disconnecting means.

Connecting the electrical system to the earth through a grounding electrode conductor and electrode (Article 250).

Joining metal parts together so they're at the same potential — creates the low-impedance fault path that trips the breaker.

Bonding does (the EGC carries fault current back to the source). The earth does NOT clear faults.

The conductor connecting the grounded system/equipment to the grounding electrode. Sized by Table 250.66.

6 AWG copper — never required to be larger, regardless of service size (made-electrode resistance limits the current).

4 AWG copper — never required to be larger, regardless of service size.

The conducting object making earth contact: ground rod, metal water pipe, concrete-encased (Ufer), or plate.

A concrete-encased electrode — rebar or wire encased in the building's concrete footing/foundation.

Bonds non-current-carrying metal back to the source, providing a low-impedance fault path so the breaker opens.

Table 250.122, by the rating of the overcurrent device protecting the circuit.

14 AWG copper.

12 AWG copper.

10 AWG copper.

8 AWG copper.

6 AWG copper.

250.118 — a copper conductor (insulated or bare), rigid/intermediate metal conduit, EMT, the metal of a listed cable, etc.

The connection at the service that bonds the grounded (neutral) conductor to the equipment ground and enclosure.

The equivalent of the main bonding jumper for a separately derived system (e.g., a transformer secondary).

The grounding-electrode-conductor table (Table 250.102 / 250.66), based on the supply conductors.

A system whose power comes from a source (transformer, generator) with no direct electrical connection to the supply conductors.

Grounded conductor = the neutral (intentionally tied to ground, carries current). Grounding conductor (EGC) = the fault path, carries no current normally.

At the service, via the main bonding jumper — neutral and equipment ground are bonded there (and only there).

Yes, if it's free from physical damage and securely fastened to the surface (6 AWG copper or larger).

To avoid parallel neutral paths on the equipment ground downstream; subpanels keep neutral and ground separate.

Stabilizes voltage to ground and dissipates lightning/surge energy. It does not clear faults.

At least the value from the GEC table for the service conductors, since it also serves as the effective ground-fault return path.

A metal underground water pipe in contact with earth 10+ ft must be used as an electrode and supplemented by an additional electrode.

At least 8 ft long, driven so its full length is in contact with the soil (top flush or below grade).

A single rod with 25 ohms or more resistance to earth must be supplemented by a second electrode (commonly two rods are just installed).

Must be readily accessible, marked, and able to disconnect all ungrounded service conductors (grouped, limited number).

A solid conductor (bar) in a panel that distributes power to the breakers; the neutral and ground each have their own bus.

No — at a subpanel the neutral (grounded) bus is isolated from the ground (bonding) bus; they bond ONLY at the service.

A reliable conductor ensuring electrical continuity between metal parts that must be bonded (e.g., around a concentric knockout).

All present electrodes (water pipe, rods, Ufer, etc.) must be bonded together to form one grounding electrode system (250.50).

An intentionally constructed, low-impedance path that carries fault current back to the source so the OCPD operates (250.4).

Conductors between the service equipment and the final branch-circuit overcurrent device (Article 215).

The conductors between the final overcurrent device and the outlets it serves (Article 210).

At least the noncontinuous load + 125% of the continuous load (before adjustment factors).

A load expected to operate for 3 hours or more. Sized at 125% for conductors and overcurrent devices.

It's the inverse of 80% — it keeps a breaker from running continuously at its full rating, which would overheat it.

Yes — treated as a continuous load, so it gets the 125% factor.

3 volt-amperes per square foot of habitable floor area (Article 220).

Add two small-appliance circuits and one laundry circuit at 1,500 VA each before applying demand factors.

First 3,000 VA at 100%, 3,001–120,000 VA at 35%, remainder at 25% (Table 220.45 in 2023 NEC; 220.42 in 2017/2020).

Loads rarely all run at full load at once; demand factors keep the service from being oversized.

Table 220.54 lets a feeder serving four or more dryers be reduced, because they don't all run at full load together.

Table 220.55 provides demand loads for household cooking equipment over 1¾ kW (e.g., one 12 kW range = 8 kW demand).

Must be at least the total calculated load of everything downstream.

Yes (Table 220.42/220.45) — e.g., warehouses get a lighting demand factor that offices don't, by expected diversity of use.

1,500 × 3 VA = 4,500 VA.

Standard method (220 Part III) sums loads with demand factors; the optional method (220.82) uses a simpler 100%/40% formula.

Service = utility to the building (Article 230). Feeder = service equipment to a downstream panel/overcurrent device (Article 215).

Store/office lighting on for the business day, electric heat — anything running 3+ hours.

Sized for the maximum unbalanced load (220.61) — the most line-to-neutral load on any one ungrounded conductor.

Ampacity for the combined calculated load of both subpanels (after their own demand factors), not just their breaker sizes.

A single continuous-duty motor's branch-circuit conductors are sized at 125% of the motor full-load current (430.22).

The NEC motor tables (e.g., Table 430.248/430.250), NOT the nameplate, for branch-circuit and feeder sizing.

Overloads (heaters/relays) protect the motor from running overcurrent; the branch-circuit breaker/fuse protects against short circuits and ground faults.

Sized at 125% of the largest motor's FLC plus the sum of the other motors' FLCs (430.24).

Connected load = everything added up; demand load = connected load after applying NEC demand factors for realistic simultaneous use.

The maximum current a conductor can carry continuously without exceeding its temperature rating (Table 310.16).

25 A — but the small-conductor rule caps its breaker at 20 A.

35 A — but the small-conductor rule caps its breaker at 30 A.

50 A.

65 A.

85 A.

100 A.

150 A.

175 A.

230 A.

Bundling more than three current-carrying conductors in a raceway derates the ampacity (310.15).

Apply the temperature correction factors of Table 310.15(B)(1) — hotter ambient lowers usable ampacity.

American Wire Gauge — the conductor sizing system. A SMALLER number means a LARGER conductor.

Thousands of circular mils — the size unit for conductors larger than 4/0 AWG (e.g., 250 kcmil).

Article 358 (electrical metallic tubing).

Secured within 3 ft of each box/termination, then supported at least every 10 ft.

No more than 360° total (four quarter-bends) between pull points.

To keep conductor pulling tension low so insulation isn't damaged during the pull.

Must be reamed to remove burrs and rough edges that could damage conductor insulation (358.28).

No — EMT is not permitted where subject to severe physical damage (358.12). Use rigid metal conduit.

Article 334 (nonmetallic-sheathed cable, 'Romex').

Dry locations and dwellings/normally dry structures. Not in wet locations or where exposed to damage.

Secured within 12 in of every box and at least every 4.5 ft along the run.

Cables smaller than two 6 AWG or three 8 AWG run through bored holes in joists or on a running board (334.15(C)).

Article 344. Heavy-wall, threaded steel; permitted in nearly all locations, including severe physical damage.

General requirements for all wiring methods — protecting from physical damage, securing/supporting conductors, raceway rules.

53% maximum (Chapter 9, Table 1).

31% maximum — the most restrictive, because a tight pair can jam during the pull.

40% maximum (Chapter 9, Table 1).

A snug pair tends to jam against the raceway wall during a pull, so the limit is lower (31% vs 40%).

2.00 cubic inches (Table 314.16(B)).

2.25 cubic inches.

2.50 cubic inches.

3.00 cubic inches.

5.00 cubic inches.

All equipment grounding conductors together count as ONE, based on the largest one present.

All internal cable clamps together count as ONE, based on the largest conductor in the box.

Each yoke/strap counts as TWO, based on the largest conductor connected to that device.

Each fixture stud or hickey counts as ONE, based on the largest conductor in the box.

5 (conductors) + 2 (yoke) + 1 (grounds) = 8 units × 2.25 in³ = 18.0 in³ minimum.

24 inches for direct-buried cables/conductors rated 0–600 V in the general location.

6 inches minimum for RMC/IMC.

18 inches for direct-buried UF cable/conductors.

12 inches (the reduced-cover column of Table 300.5).

Table 300.5 generally requires a warning ribbon placed in the trench above buried conductors at the listed depth.

Insulated/bare copper, RMC, IMC, EMT, the metal sheath of certain cables, and listed flexible conduits under conditions.

Must be increased proportionally (250.122(B)) so the fault path keeps pace.

Must be in the SAME raceway/cable to avoid inductive heating (the magnetic fields must cancel).

Thermoplastic, High heat-resistant, Nylon-coated — a common 90°C dry-location building wire.

Burrs left on the inside of a cut raceway can slice conductor insulation when wires are pulled.

Rigid metal conduit (RMC) — not EMT.

Conductor cross-sectional area — the area of a circle 1 mil (0.001 in) in diameter; more circular mils = larger wire.

No — it carries current only during a ground fault. The neutral (grounded conductor) carries normal current.

An enclosed channel (conduit, tubing, wireway) designed expressly to hold conductors.

MC (Article 330) has a metal interlocking armor and is allowed in more locations; NM (Article 334) has a nonmetallic sheath, mainly for dry dwellings.

A fitting that provides access for pulling/splicing conductors at a bend or junction in a raceway run.

Article 348 — for connections to equipment subject to movement/vibration (e.g., motors); length and EGC limits apply.

Article 350 (LFMC) — flexible connections in wet/damp/oily locations, such as outdoor motor connections.

Use raceways/cables/conductors listed for wet locations (e.g., RMC, PVC, THWN conductors); NM cable is not allowed in wet locations.

Rigid nonmetallic conduit (Article 352) — corrosion-resistant; common for underground and wet locations; needs expansion fittings for movement.

White or gray. The EGC is green, green/yellow, or bare. Ungrounded (hot) conductors are any other color.

Heat from each conductor can't dissipate as easily when crowded, so the allowable ampacity is reduced (310.15).

An enclosure where conductors are spliced or pulled; must remain accessible and meet box-fill and pull-box sizing rules.

Length at least 8 times the largest raceway's trade size (314.28).

Distance from the raceway entry to the opposite wall at least 6 times the largest raceway's trade size (314.28).

A fuse or circuit breaker that opens the circuit when current would overheat the conductor (Article 240).

The CONDUCTOR (and equipment) from excessive current/heat — not the load.

Handle no more than 6 ft 7 in above the floor or platform (240.24); not over steps, in bathrooms, or in clothes closets.

Maximum 15 A overcurrent device, regardless of the higher ampacity-table value.

Maximum 20 A overcurrent device.

Maximum 30 A overcurrent device.

Yes. 240.4(D) caps 12 AWG copper at 20 A even if the 90°C ampacity is higher.

A conductor with overcurrent protection ahead of it larger than its ampacity normally allows; permitted under the tap rules.

Tap ≤10 ft must have ampacity ≥ the computed load and ≥ the rating of the device it supplies.

Tap ≤25 ft must have ampacity ≥ one-third the rating of the overcurrent device protecting the feeder.

PEOPLE — it protects against electric shock by sensing current leaking to ground.

A small ground-fault current imbalance of about 4–6 milliamperes (mA).

It compares current out (hot) to current back (neutral); any imbalance means leakage to ground, so it trips in milliseconds.

210.8 (dwelling-unit and other GFCI requirements).

Kitchens (countertops), bathrooms, garages, unfinished basements, outdoors, laundry areas, and near sinks.

PROPERTY — it protects against fire by detecting dangerous arcing faults.

210.12 (arc-fault circuit-interrupter protection).

Most 120 V, 15- and 20-A branch circuits in dwelling living areas — bedrooms, living rooms, dens, hallways, etc.

GFCI guards against the shock to a person near Ground/water; AFCI guards against the Arc that starts a fire.

Yes — extending/modifying a branch circuit in an AFCI-required dwelling area generally requires AFCI protection (210.12).

The replacement must be provided with GFCI protection (210.8 applies to replacements in those locations).

No point along a wall line is more than 6 ft from a receptacle, so receptacles are ≤12 ft apart.

Any wall space 2 ft or wider (measured along the floor line, around corners, not crossing doorways).

No point along the counter wall line is more than 24 in from a receptacle (210.52(C)).

Any counter 12 in or wider.

3 feet (36 in) of clear depth in front of the equipment (110.26).

30 inches, or the width of the equipment, whichever is greater.

At least 6½ feet (78 in) of clear headroom.

Doors/hinged panels must open at least 90 degrees.

No — it must be kept clear at all times.

Increases to 3½ ft (Condition 2) and 4 ft (Condition 3) when grounded or live parts face the working space (≤150 V).

Treat every conductor and part as energized until it is tested and proven de-energized.

OSHA 1910.147 procedure: de-energize, lock the disconnect off, tag it, and verify dead with a meter before servicing.

OSHA (e.g., 1910 General Industry, 1926 Construction); the NEC governs the installation itself.

To protect against shock, arc flash, and burns — insulated gloves/tools, arc-rated clothing, eye and face protection.

An explosive release of energy from an electrical fault arc, producing intense heat, light, and pressure — a major hazard.

A breaker/conductor serving a continuous load must be sized at 125% of that load (210.20, 215.3).

The branch breaker must protect the smallest conductor; the feeder OCPD protects the feeder, coordinated so faults clear at the right level.

The branch-circuit breaker. The breaker protects the wire from overload; the GFCI protects people from shock — different jobs.

No — it senses leakage to ground regardless, so it can protect even on a circuit without an EGC.

A 20 A circuit dedicated to bathroom receptacles (210.11), and those receptacles must be GFCI-protected.

At least two 20 A small-appliance branch circuits for countertop receptacles (210.11/210.52(B)).

A branch circuit that supplies only one piece of utilization equipment (e.g., a dishwasher or a fixed motor).

Panels/overcurrent devices can't be in bathrooms or over steps; readiness, dryness, and access are the concerns (240.24).

Enough to serve the computed general lighting load (3 VA/ft²) at the circuit rating (210.11(A)).

Designing overcurrent protection so only the device nearest a fault opens, leaving the rest of the system energized.

AFCI (arc-fault) — bedrooms are dwelling living areas. GFCI (ground-fault) goes in wet/grounded areas.

A device that provides BOTH GFCI and AFCI protection in one — useful where both are required (e.g., a kitchen).

Required in dwelling units for 125 V, 15- and 20-A receptacles (406.12) to prevent children inserting objects.

A point on the wiring system where current is taken to supply utilization equipment — not just a receptacle.

The breaker's job is to open before the conductor overheats; a breaker too large for the wire defeats that protection.