Journeyman Electrician (NEC) — All Questions

On a 208Y/120-volt wye system, what is the relationship between line current and phase current?

• a.Line current equals phase current divided by 1.732
• b.Line current equals 3 times phase current
• c.Line current equals 1.732 times phase current
• d.Line current equals phase current✓

In a wye configuration the line current equals the phase current, while the line voltage is 1.732 times the phase voltage. In a delta configuration those relationships reverse.

A 240-volt single-phase feeder supplies an 8-kilowatt continuous load. What is the minimum standard overcurrent device rating?

• a.45 amperes✓
• b.35 amperes
• c.50 amperes
• d.40 amperes

Load current = 8,000 / 240 = 33.3 A. Because the load is continuous, the device must be at least 33.3 x 1.25 = 41.7 A, so the next standard rating is 45 A. See NEC 210.20(A) and 240.6(A).

A plate electrode must present at least how much surface area to exterior soil?

• a.8 square feet
• b.4 square feet
• c.2 square feet✓
• d.1 square foot

A plate electrode of iron, steel or nonferrous metal must expose at least 2 square feet of surface to the surrounding earth. See NEC 250.52(A)(7).

What is the maximum support spacing for a 2-inch trade size rigid PVC conduit?

• a.6 feet
• b.3 feet
• c.5 feet✓
• d.8 feet

PVC support spacing depends on trade size: 1/2 through 1 inch every 3 feet, and 1 and 1/4 through 2 inch every 5 feet. See NEC 352.30(B).

For that two-motor feeder, if the largest branch-circuit protective device is 90 amperes, what is the maximum feeder overcurrent device rating?

• a.100 amperes
• b.111 amperes
• c.125 amperes
• d.110 amperes✓

The feeder device may not exceed the largest branch device plus the other motors' full-load currents: 90 + 21 = 111 A. Since 111 is not standard and this is a maximum, the next lower standard size of 110 A is used. See NEC 430.62(A).

A single-phase transformer has a 240-volt primary and a 48-volt secondary. If the secondary carries 50 amperes, what is the approximate primary current?

• a.5 amperes
• b.10 amperes✓
• c.50 amperes
• d.250 amperes

Voltage and current transform inversely and the volt-amperes match: 240 x I = 48 x 50, so I = 2,400 / 240 = 10 amperes. Inverting the ratio gives the 250-ampere trap.

Along a dwelling kitchen countertop, no point measured horizontally along the wall line may be more than what distance from a receptacle outlet?

• a.36 inches
• b.24 inches✓
• c.48 inches
• d.12 inches

No point along the kitchen counter wall line may be more than 24 inches from a receptacle, which places outlets no more than 48 inches apart. See NEC 210.52(C)(1).

When ungrounded conductors are increased in size for voltage drop, how must the equipment grounding conductor be adjusted?

• a.Doubled in every case
• b.Increased proportionally to the ungrounded conductors' increase in circular-mil area✓
• c.Sized only from Table 250.122 by the overcurrent device rating
• d.Left unchanged because the overcurrent device did not change

Where ungrounded conductors are upsized, the equipment grounding conductor must be increased proportionally by circular-mil area. See NEC 250.122(B).

A cable is run through a notch cut in the edge of a wood stud. What is required to protect it?

• a.A plastic bushing of any thickness
• b.A steel plate at least 1/8 inch thick
• c.A steel plate at least 1/16 inch thick installed across the notch✓
• d.No protection if the cable is stapled at the notch

Where a cable is laid in a notch, a steel plate, sleeve or clip at least 1/16 inch thick must protect it from screws and nails. See NEC 300.4(A)(2).

An air-conditioning condensing unit is marked minimum circuit ampacity 28.4 amperes. Using 75 degrees C copper, what is the minimum branch-circuit conductor size?

• a.8 AWG copper
• b.14 AWG copper
• c.10 AWG copper✓
• d.12 AWG copper

The minimum circuit ampacity sizes the conductors: 28.4 A calls for 10 AWG copper (35 A at 75 degrees C). See NEC 440.32 and 440.4(B).

What is the secondary full-load current of a 15 kVA single-phase transformer with a 240-volt secondary?

• a.62.5 amperes✓
• b.125 amperes
• c.31 amperes
• d.104 amperes

For a single-phase transformer, I = VA / E = 15,000 / 240 = 62.5 amperes.

A kitchen countertop or work surface must have a receptacle outlet if it is at least what width?

• a.12 inches✓
• b.18 inches
• c.6 inches
• d.24 inches

A countertop or work surface that is 12 inches or wider must be provided with at least one receptacle outlet. See NEC 210.52(C)(1).

A service is supplied by a single set of 350 kcmil copper ungrounded conductors. What is the minimum size copper main bonding jumper?

• a.3 AWG
• b.1/0 AWG
• c.2 AWG✓
• d.4 AWG

The main bonding jumper is sized from Table 250.102(C)(1), and 350 kcmil copper falls in the over 3/0 through 350 kcmil row requiring 2 AWG copper. See NEC 250.28(D)(1).

A pull box is used for a straight pull, and the largest raceway entering it is 4-inch trade size. What is the minimum length of the box in the direction of the pull?

• a.16 inches
• b.24 inches
• c.32 inches✓
• d.48 inches

For straight pulls the box length must be at least eight times the trade size of the largest raceway: 8 x 4 = 32 inches. See NEC 314.28(A)(1).

A hermetic refrigerant motor-compressor has a rated-load current of 22 amperes. What is the maximum branch-circuit short-circuit and ground-fault protective device at the standard 175 percent?

• a.45 amperes
• b.50 amperes
• c.40 amperes✓
• d.35 amperes

Protection is sized at not more than 175 percent of the rated-load current: 22 x 1.75 = 38.5 A, and the next standard size is 40 A. See NEC 440.22(A).

How much energy does a 2,000-watt load consume when operated continuously for 3 hours?

• a.666 watt-hours
• b.2 kilowatt-hours
• c.6 kilowatt-hours✓
• d.0.67 kilowatt-hour

Energy equals power multiplied by time: 2,000 watts x 3 hours = 6,000 watt-hours, or 6 kilowatt-hours.

At least one receptacle outlet must be installed within what distance of the outside edge of each dwelling bathroom basin?

• a.6 feet
• b.3 feet✓
• c.2 feet
• d.1 foot

A receptacle must be located within 3 feet of the outside edge of each basin, on a wall or partition adjacent to the basin or on the basin countertop. See NEC 210.52(D).

A service uses two parallel sets of 600 kcmil copper conductors per phase. Using the 12.5 percent rule, what is the minimum copper main bonding jumper?

• a.2/0 AWG
• b.4/0 AWG
• c.3/0 AWG✓
• d.250 kcmil

Where copper service conductors exceed 1,100 kcmil, the main bonding jumper must be at least 12.5 percent of that area: 2 x 600 = 1,200 kcmil, and 1,200 x 0.125 = 150 kcmil. 2/0 (133.1 kcmil) is too small; 3/0 (167.8 kcmil) qualifies. See NEC 250.28(D)(2).

An angle pull box has a 3-inch raceway and a 2-inch raceway entering the same wall with conductors turning 90 degrees. What is the minimum distance from that wall to the opposite wall?

• a.13 inches
• b.20 inches✓
• c.24 inches
• d.18 inches

For angle pulls the distance is six times the largest raceway plus the sum of the other raceway diameters on the same wall: (6 x 3) + 2 = 20 inches. See NEC 314.28(A)(2).

For that same 22-ampere rated-load compressor supplied alone, what minimum conductor ampacity is required?

• a.30 amperes
• b.22 amperes
• c.38.5 amperes
• d.27.5 amperes✓

Branch-circuit conductors for a single motor-compressor must be at least 125 percent of the rated-load or branch-circuit selection current: 22 x 1.25 = 27.5 A, which calls for 10 AWG copper. See NEC 440.32.

A 30-ohm resistor and a 60-ohm resistor are connected in series across a 90-volt source. What is the voltage drop across the 60-ohm resistor?

• a.60 volts✓
• b.30 volts
• c.90 volts
• d.45 volts

Total resistance is 30 + 60 = 90 ohms, so the current is 90 / 90 = 1 ampere. The drop across the 60-ohm resistor is 1 x 60 = 60 volts, and 30 volts appears across the 30-ohm resistor.

What is the minimum branch-circuit rating required for the dwelling laundry receptacle outlet(s)?

• a.15 amperes
• b.30 amperes
• c.20 amperes✓
• d.25 amperes

At least one 20-ampere branch circuit must supply the laundry receptacle outlet(s), and it may not serve other outlets. See NEC 210.11(C)(2) and 210.52(F).

A reinforcing bar used to form a concrete-encased electrode must be at least what diameter?

• a.1/4 inch
• b.5/8 inch
• c.3/8 inch
• d.1/2 inch✓

A concrete-encased electrode may use at least 20 feet of electrically conductive reinforcing bar not smaller than 1/2 inch in diameter, encased in at least 2 inches of concrete. See NEC 250.52(A)(3).

How must flexible metal conduit (FMC) be secured on a normal run?

• a.Within 12 inches of each box or fitting and at intervals not exceeding 4 and 1/2 feet✓
• b.Within 3 feet of each box and at intervals not exceeding 10 feet
• c.Within 12 inches of each box and at intervals not exceeding 6 feet
• d.Support is never required for FMC

FMC is secured within 12 inches of each box, cabinet or fitting and supported at intervals not exceeding 4 and 1/2 feet, with limited exceptions for flexibility. See NEC 348.30(A).

A recessed luminaire with a completely enclosed light source is installed in a clothes closet. What is the minimum clearance from the nearest point of the defined storage space?

• a.6 inches✓
• b.3 inches
• c.18 inches
• d.12 inches

A recessed luminaire with a completely enclosed light source may be as close as 6 inches to the storage space, while a surface-mounted enclosed luminaire requires 12 inches. See NEC 410.16(C)(2).

A 480-volt panelboard is mounted so there are no live or grounded parts opposite the working space. What is the minimum required depth of working space?

• a.3 feet✓
• b.3 and 1/2 feet
• c.2 and 1/2 feet
• d.4 feet

For 151 to 600 volts to ground, Condition 1 (no live or grounded parts opposite) requires 3 feet of depth. Condition 2 requires 3 and 1/2 feet and Condition 3 requires 4 feet. See NEC 110.26(A)(1).

Using the standard method, what is the general lighting load for a 2,500-square-foot dwelling before demand factors?

• a.5,625 volt-amperes
• b.11,250 volt-amperes
• c.7,500 volt-amperes✓
• d.6,000 volt-amperes

Dwelling general lighting is 3 volt-amperes per square foot: 2,500 x 3 = 7,500 VA. See NEC Table 220.12; verify the VA-per-square-foot value for the NEC edition your jurisdiction has adopted.

Where two rod electrodes are installed to form the grounding electrode system, what is the minimum spacing between them?

• a.6 feet✓
• b.8 feet
• c.3 feet
• d.10 feet

Supplementary rods must be at least 6 feet apart so their earth shells do not overlap. The 8-foot figure is the rod length, not the spacing. See NEC 250.53(A)(3).

What is the minimum burial cover for any wiring method installed directly beneath a public street, road or driveway?

• a.12 inches
• b.6 inches
• c.18 inches
• d.24 inches✓

Under streets, highways, roads, alleys, driveways and parking lots, all listed wiring methods require 24 inches of cover. See NEC Table 300.5(A).

A recessed luminaire not identified for insulation contact must be spaced at least what distance from combustible materials, other than at points of support?

• a.1 inch
• b.1/2 inch✓
• c.3 inches
• d.6 inches

A non-IC recessed luminaire must be at least 1/2 inch from combustible materials, other than at the points of support, and 3 inches from thermal insulation. See NEC 410.116(A)(1).

A 480-volt panelboard has exposed energized parts on both sides of the working space. What is the minimum required depth of working space?

• a.3 feet
• b.5 feet
• c.4 feet✓
• d.3 and 1/2 feet

For 151 to 600 volts to ground, Condition 3, with exposed live parts on both sides of the working space, requires a depth of 4 feet. See NEC 110.26(A)(1).

An apartment has the two required small-appliance branch circuits and no laundry circuit. What load must be included for the small-appliance circuits before demand factors?

• a.3,000 volt-amperes✓
• b.6,000 volt-amperes
• c.4,500 volt-amperes
• d.1,500 volt-amperes

Each small-appliance branch circuit is calculated at 1,500 VA: 2 x 1,500 = 3,000 VA. See NEC 220.52(A).

A single ground rod need not be supplemented by a second electrode if its resistance to earth does not exceed what value?

• a.25 ohms✓
• b.1 ohm
• c.5 ohms
• d.100 ohms

A single rod, pipe or plate electrode must be supplemented unless it is shown to have a resistance to earth of 25 ohms or less. See NEC 250.53(A)(2).

What is the smallest conductor size generally permitted for building branch-circuit wiring?

• a.18 AWG copper
• b.14 AWG copper✓
• c.16 AWG copper
• d.12 AWG copper

For general branch-circuit and building wiring the smallest conductor is 14 AWG copper; 18 and 16 AWG are permitted only for specific limited applications such as fixture wire and some Class 2 circuits. See NEC 310.106(A) and Table 310.16.

A generator nameplate current rating is 150 amperes. What minimum conductor size is required from the generator terminals to the first overcurrent device, using 75 degrees C copper?

• a.3/0 AWG
• b.2/0 AWG✓
• c.1 AWG
• d.1/0 AWG

Conductors from the generator terminals to the first device must be at least 115 percent of the nameplate current: 150 x 1.15 = 172.5 A. In the 75 degrees C column 1/0 (150 A) fails and 2/0 (175 A) qualifies. See NEC 445.13(A).

What is the minimum headroom of the working space about electrical equipment such as panelboards?

• a.6 and 1/2 feet✓
• b.3 feet
• c.7 feet
• d.6 feet

The minimum headroom of working space is 6 and 1/2 feet, or the height of the equipment if taller. See NEC 110.26(A)(3).

Using Column C of the household cooking-appliance demand table, what is the demand load for two 12-kilowatt household ranges on one feeder?

• a.11 kilowatts✓
• b.10 kilowatts
• c.8 kilowatts
• d.16 kilowatts

Column C of Table 220.55 gives 11 kilowatts for two household ranges rated not over 12 kilowatts each. See NEC 220.55.

A concrete-encased electrode using bare copper must be formed with at least 20 feet of what minimum conductor size?

• a.2 AWG
• b.4 AWG✓
• c.8 AWG
• d.6 AWG

A concrete-encased electrode may be at least 20 feet of bare copper not smaller than 4 AWG, or 20 feet of 1/2-inch or larger reinforcing bar, encased near the bottom of a footing. See NEC 250.52(A)(3).

At least one required 125-volt receptacle serving a permanently installed pool must be located within what distance range from the inside pool wall?

• a.Between 10 feet and 25 feet
• b.Between 6 feet and 20 feet✓
• c.Between 5 feet and 15 feet
• d.Between 3 feet and 10 feet

A general-use receptacle must be no closer than 6 feet, and at least one required receptacle must be located between 6 and 20 feet from the inside pool wall. See NEC 680.22(A).

A photovoltaic source circuit uses modules with a rated short-circuit current of 8 amperes. What minimum conductor ampacity is required before any adjustment factors?

• a.15.6 amperes
• b.12.5 amperes✓
• c.8 amperes
• d.10 amperes

The maximum circuit current is 125 percent of the rated short-circuit current: 8 x 1.25 = 10 A, and the conductor is then sized at 125 percent of that value: 10 x 1.25 = 12.5 A. See NEC 690.8(A) and (B).

Working spaces about service equipment, switchboards, panelboards or motor control centers installed indoors must be provided with what?

• a.A dedicated telephone
• b.Illumination✓
• c.A portable fire extinguisher
• d.A rubber grounding mat

Indoor working spaces about service equipment, switchboards, panelboards and motor control centers must have illumination. See NEC 110.26(D).

Using the standard demand table, what is the demand load for a single 16-kilowatt household electric range?

• a.8 kilowatts
• b.16 kilowatts
• c.9.6 kilowatts✓
• d.12 kilowatts

Column C for one range is 8 kilowatts. Note 1 increases that value 5 percent for each kilowatt over 12: 16 kW is 4 over, so 8 x 1.20 = 9.6 kilowatts. See NEC Table 220.55, Note 1.

Where rock bottom is encountered and an 8-foot rod cannot be driven vertically, at what maximum angle from vertical may the rod be driven?

• a.90 degrees
• b.45 degrees✓
• c.60 degrees
• d.30 degrees

If rock bottom prevents vertical driving, a rod electrode may be driven at an angle not exceeding 45 degrees from vertical, or buried in a trench at least 30 inches deep. See NEC 250.53(G).

A location where combustible dust is present in ignitible concentrations is classified as which type?

• a.Class IV
• b.Class II✓
• c.Class I
• d.Class III

Class II locations are those made hazardous by combustible dust. Class I covers flammable gases and vapors and Class III covers ignitible fibers and flyings. See NEC 500.5(C).

A continuous-duty motor with no marked service factor and no marked temperature rise will not start because the overload device selected at the basic percentage keeps tripping. To what maximum percentage of nameplate current may the overload device be increased?

• a.125 percent
• b.150 percent
• c.130 percent✓
• d.140 percent

Motors that do not have a service factor of 1.15 or greater or a marked temperature rise of 40 degrees C or less may be increased only to 130 percent, while better-rated motors may go to 140 percent. See NEC 430.32(C).

Under the Article 100 definitions, what does it mean to connect equipment to the earth?

• a.Grounding✓
• b.Insulating
• c.Bonding
• d.Derating

Grounding is the connection to earth or to a conductive body that extends the earth connection, while bonding is the connection of parts together for electrical continuity. See NEC Article 100.

A dwelling has a single household electric clothes dryer with a nameplate rating of 5.5 kilowatts. What value must be used for the dryer load?

• a.4,000 volt-amperes
• b.5,000 volt-amperes
• c.5,250 volt-amperes
• d.5,500 volt-amperes✓

The dryer load is 5,000 VA or the nameplate rating, whichever is larger: 5,500 exceeds 5,000, so 5,500 VA is used. See NEC 220.54.

A grounding electrode conductor connection to a ground rod buried in the earth must use what kind of fitting?

• a.A connector or clamp listed for direct burial in soil✓
• b.A tape-wrapped mechanical lug
• c.A solder joint
• d.Any indoor split-bolt connector

Connections to electrodes in contact with earth must be made with fittings listed and identified for direct soil or concrete burial as applicable. See NEC 250.70 and 250.68(A).

A 15-ampere, 125-volt receptacle is installed in a damp location such as under a roofed open porch. What cover is required?

• a.A cover that is weatherproof when no attachment plug is inserted✓
• b.A cover that is weatherproof whether or not a plug is inserted
• c.No cover is required in a damp location
• d.A standard indoor wall plate

In damp locations a receptacle needs an enclosure weatherproof when a plug is not inserted; the stricter in-use cover, weatherproof with a plug inserted, is required in wet locations. See NEC 406.9(A).

How many running overload protective devices are required for a single-phase, two-wire alternating-current motor?

• a.One✓
• b.Three
• c.Four
• d.Two

Table 430.37 requires one overload device in one ungrounded conductor for a single-phase, two-wire motor, whereas a three-phase motor requires one in each of the three phases. See NEC Table 430.37.