CSLB Trade — Electrical (C-10) — All Questions

Each multiwire branch circuit must be provided with a means to simultaneously disconnect all what, at the point where the branch circuit originates?

• a.Ungrounded conductors✓
• b.Neutral conductors only
• c.Grounded conductors
• d.Equipment grounding conductors

Section 210.4(B) requires a means to simultaneously disconnect all ungrounded (hot) conductors of a multiwire branch circuit at the point of origin, typically a handle tie or common-trip breaker. This prevents shock when servicing a shared neutral. Grounded, equipment grounding, and neutral-only choices misstate the rule.2023 NEC §210.4(B)

In a dwelling unit, the voltage between conductors supplying lampholders, luminaires, and 15- and 20-ampere receptacles must not exceed what value?

• a.208 V
• b.277 V
• c.240 V
• d.120 V✓

Section 210.6(A) limits circuits supplying lampholders and standard 15- and 20-A receptacles in dwellings to 120 V between conductors. Higher voltages such as 208, 240, and 277 V are permitted only for specific equipment and larger circuits, not general dwelling lighting and receptacle circuits.2023 NEC §210.6(A)

Under the 2023 NEC, how may a receptacle be installed to serve a kitchen countertop or work surface?

• a.Up to 12 inches below the countertop, if the overhang is 6 inches or less
• b.Face-up in the countertop surface, as long as it is within 6 inches of the edge
• c.In the wall cabinet above the counter, within 30 inches of the surface
• d.On or above the countertop, not more than 20 inches above it (face-up only if listed for countertop use)✓

2023 NEC 210.52(C)(3) requires kitchen countertop receptacles to be on or above the counter, not more than 20 in (500 mm) above it; a face-up receptacle in the surface is allowed only if listed for countertop/work-surface use. Below-counter mounting (formerly permitted up to 12 in below) was removed in the 2020 NEC, and there is no allowance for face-up within 6 in of the edge or placement in the upper cabinet.2023 NEC §210.52(C)(3)

A receptacle outlet serving a dwelling countertop must be located not more than what distance above the countertop surface?

• a.20 in✓
• b.18 in
• c.12 in
• d.24 in

Section 210.52(C)(5) requires countertop receptacle outlets to be located not more than 20 in above the countertop. This keeps the receptacle within reach of countertop appliances. 12 and 18 in are stricter than required; 24 in exceeds the code maximum height.2023 NEC §210.52(C)(3)

In a dwelling, at least one wall switch-controlled lighting outlet must be installed in which of the following?

• a.Every habitable room and bathroom✓
• b.Only bedrooms
• c.Only bathrooms
• d.Only the kitchen

Section 210.70(A)(1) requires at least one wall switch-controlled lighting outlet in every habitable room and bathroom of a dwelling. Limiting it to only the kitchen, only bedrooms, or only bathrooms would leave other required rooms without switched lighting.2023 NEC §210.70(A)(1)

For equipment rated 1200 amperes or more and over 6 ft wide containing overcurrent devices, how many entrances of adequate size are required to give access to the working space?

• a.None required
• b.One total
• c.One at each end (two total)✓
• d.Three total

Section 110.26(C)(2) requires one entrance not less than 24 in wide and 6.5 ft high at each end of the working space for equipment rated 1200 A or more and over 6 ft wide, giving two entrances. A single entrance may be allowed only under specific exceptions. Three and 'none' are incorrect.2023 NEC §110.26(C)(2)

The dedicated equipment space above a panelboard indoors extends from the top of the equipment to what height, or to the structural ceiling if lower?

• a.6 ft✓
• b.4 ft
• c.3 ft
• d.10 ft

Section 110.26(E)(1)(a) requires the dedicated space above indoor electrical equipment such as panelboards to extend 6 ft above the equipment or to the structural ceiling, whichever is lower, kept clear of foreign piping and ducts. 3 and 4 ft are too little; 10 ft is more than the code requires.2023 NEC §110.26(E)

At each conductor splice point, outlet, switch point, or junction in a raceway or cable system, what must generally be installed?

• a.A box or conduit body✓
• b.An expansion fitting
• c.A bushing
• d.A grounding clamp

Section 300.15 requires a box or conduit body at each splice, outlet, switch, junction, or pull point in raceway and cable systems, providing access and enclosure for connections. A grounding clamp, expansion fitting, and bushing serve other purposes and do not satisfy this enclosure requirement.2023 NEC §300.15

Raceways, cable assemblies, boxes, and fittings must be securely fastened in place. Support wires that do not provide secure support are permitted only if what condition is met?

• a.They are at least 12 gauge
• b.They are painted
• c.They are copper
• d.An independent means of secure support is provided✓

Section 300.11(A) requires electrical wiring to be securely fastened and prohibits using ceiling-support wires unless an independent means of secure support is provided. The color, metal type, or gauge of a wire does not by itself satisfy the secure-support requirement.2023 NEC §300.11(A)

When counting conductors for box fill in a device box, each 14 AWG current-carrying conductor that originates outside the box and terminates or is spliced within it counts as how many conductors?

• a.One-half
• b.Two
• c.One✓
• d.Zero

Section 314.16(B)(1) counts each conductor that runs through the box or terminates in it as one conductor for box-fill volume. A 14 AWG conductor entering and terminating counts as one at 2.0 cubic inches. Counting it as two, one-half, or zero would misapply the box-fill calculation.2023 NEC §314.16

A 125-volt receptacle located within 6 ft of the outside edge of a bathtub or shower stall in a dwelling requires what protection?

• a.GFCI✓
• b.No protection
• c.AFCI only
• d.Surge only

Section 210.8(A)(9) requires GFCI protection for receptacles located within 6 ft of the outside edge of a bathtub or shower stall because of the wet environment. AFCI alone protects against arcing, not shock; 'no protection' and surge-only do not meet the requirement.2023 NEC §210.8(A)(9)

Under 210.8(F), outdoor outlets for dwellings supplying equipment such as air-conditioning condensers, rated 150 volts or less to ground and 60 amperes or less, generally require what?

• a.Surge protection
• b.GFCI protection✓
• c.No protection
• d.AFCI protection

Section 210.8(F) requires GFCI protection for outdoor outlets that supply dwelling equipment rated 150 V or less to ground and 60 A or less, including many HVAC condenser units. AFCI and surge protection do not address the outdoor shock hazard, and 'no protection' does not meet the rule.2023 NEC §210.8(F)

In an attached dwelling garage with two vehicle bays, at least how many receptacle outlets are required, and in what location?

• a.At least one in each vehicle bay✓
• b.One near the door only
• c.None
• d.One total, any wall

Section 210.52(G)(1) requires at least one receptacle outlet installed in each vehicle bay of a dwelling garage, not more than 5.5 ft above the floor. A two-bay garage therefore needs at least two. 'One total,' 'one near the door,' and 'none' do not satisfy the per-bay requirement.2023 NEC §210.52(G)(1)

A dwelling attached garage requires at least one branch circuit of what rating to supply the required garage receptacle outlets?

• a.120-volt, 20-ampere✓
• b.120-volt, 40-ampere
• c.240-volt, 30-ampere
• d.120-volt, 15-ampere

Section 210.11(C)(4) requires at least one 120-V, 20-A branch circuit to supply the receptacle outlets required in an attached garage, and it generally must not serve outlets outside the garage. A 15-A circuit is too small, and the 30-A and 40-A options are not the specified minimum.2023 NEC §210.11(C)(4)

A 125-volt, 15- or 20-ampere receptacle outlet for servicing must be installed within what distance of heating, air-conditioning, and refrigeration equipment?

• a.25 ft✓
• b.10 ft
• c.15 ft
• d.50 ft

Section 210.63 requires a 125-V, single-phase, 15- or 20-A receptacle within 25 ft of HVAC and refrigeration equipment, and on the same level, for servicing. 15 and 10 ft are stricter than required; 50 ft exceeds the maximum distance the code allows for the service receptacle.2023 NEC §210.63

Bends in electrical metallic tubing (EMT) must be made so that which of the following is true?

• a.The radius is as tight as possible
• b.The tubing is heated first
• c.At least six bends are used
• d.The tubing is not damaged and its internal diameter is not effectively reduced✓

Section 358.24 requires EMT bends to be made so the tubing is not damaged and the internal diameter is not effectively reduced, using at least the radius shown in Chapter 9, Table 2. Kinking or flattening the tubing violates this. Heating EMT, forcing the tightest radius, or a fixed number of bends are not the standard.2023 NEC §358.24

Direct-buried conductors or cables emerging from grade must be protected by enclosures or raceways from the required cover depth up to what height above finished grade?

• a.5 ft
• b.6 ft
• c.8 ft✓
• d.3 ft

Section 300.5(D)(1) requires direct-buried conductors and cables emerging from grade to be protected by enclosures or raceways from the required burial depth to at least 8 ft above finished grade. Lower heights of 3, 5, and 6 ft leave the emerging conductors exposed to physical damage.2023 NEC §300.5(D)(1)

Rigid polyvinyl chloride conduit (PVC) is permitted to be used in which of the following locations?

• a.Only where exposed to sunlight
• b.Only inside metal enclosures
• c.Only in dry indoor locations
• d.Wet locations and direct burial where listed✓

Section 352.10 permits rigid PVC conduit in wet locations, corrosive environments, concealed work, and direct burial where properly listed and assembled. Restricting it to dry indoor use, sunlight-only, or inside metal enclosures misstates its permitted uses. PVC is widely used underground for branch-circuit feeders.2023 NEC §352.10

Electrical metallic tubing (EMT) is generally not permitted to be used in which condition?

• a.Concealed in walls
• b.Exposed on masonry
• c.Where subject to severe physical damage✓
• d.In dry indoor locations

Section 358.12 prohibits EMT where subject to severe physical damage. EMT is permitted concealed in walls, in dry locations, and exposed on masonry when properly supported and protected. Only the severe-physical-damage condition is a listed prohibition among these choices.2023 NEC §358.12

Liquidtight flexible metal conduit (LFMC) is especially suited for which of the following uses?

• a.Connections to equipment where flexibility and protection from liquids are needed✓
• b.As a general lighting raceway in dry ceilings only
• c.Only for direct burial without fittings
• d.Only for service-entrance conductors

Section 350.10 permits LFMC where flexibility or protection from liquids, vapors, or solids is required, such as connections to motors and outdoor equipment. It is not limited to dry ceilings, is not intended specifically for service-entrance conductors, and requires listed fittings rather than bare direct burial.2023 NEC §350.10

Rigid metal conduit (RMC) is permitted to be used under which of the following conditions?

• a.In all atmospheric conditions and occupancies✓
• b.Only in dwellings
• c.Only where concealed
• d.Only in dry locations

Section 344.10 permits RMC in all atmospheric conditions and occupancies, with appropriate corrosion protection where needed. It is one of the most robust raceways. Limiting it to dry, concealed, or dwelling-only uses understates the broad permission the code grants RMC.2023 NEC §344.10

Cables or raceways installed under metal-corrugated sheet roof decking must be kept at least what distance from the lowest surface of the roof decking to the top of the raceway or cable?

• a.2 in
• b.1 in
• c.3/4 in
• d.1-1/2 in✓

Section 300.4(E) requires cables and raceways under metal-corrugated sheet roof decking to be kept at least 1-1/2 in from the lowest surface of the decking, protecting the wiring from roofing screws. The smaller 3/4-in and 1-in distances are insufficient, and 2 in is more than the code minimum.2023 NEC §300.4(E)

What is the minimum working-space depth for electrical equipment operating at 151 to 600 volts to ground under Condition 2 (exposed live parts on one side and grounded parts on the other)?

• a.3.5 ft✓
• b.4 ft
• c.3 ft
• d.2.5 ft

Table 110.26(A)(1) requires 3.5 ft of working clearance for 151-600 V to ground under Condition 2. Condition 1 at that voltage is 3 ft and Condition 3 is 4 ft. 2.5 ft is below any required minimum in this range.2023 NEC §110.26(A)(1)

In a commercial (other than dwelling) building, a 125-volt, 20-ampere receptacle installed in a bathroom must have what protection?

• a.Surge only
• b.AFCI only
• c.No protection
• d.GFCI✓

Section 210.8(B) requires GFCI protection for 125-V through 250-V receptacles in non-dwelling bathrooms, kitchens, rooftops, and similar locations. AFCI is not the specified requirement here; 'no protection' and surge-only leave the shock hazard unaddressed.2023 NEC §210.8(B)

Under 240.4(D), what is the maximum overcurrent protection permitted for a 14 AWG copper branch-circuit conductor, absent a specific exception?

• a.15 A✓
• b.25 A
• c.30 A
• d.20 A

Section 240.4(D)(3) limits 14 AWG copper conductors to a maximum overcurrent device of 15 A. This is why 14 AWG is used on 15-A branch circuits. 20, 25, and 30 A all exceed the small-conductor protection limit for 14 AWG copper.2023 NEC §240.4(D)

Under 240.4(D), what is the maximum overcurrent protection permitted for a 12 AWG copper branch-circuit conductor, absent a specific exception?

• a.30 A
• b.20 A✓
• c.25 A
• d.40 A

Section 240.4(D)(5) limits 12 AWG copper conductors to a maximum overcurrent device of 20 A, which is why 12 AWG is standard for 20-A branch circuits. 25, 30, and 40 A all exceed the small-conductor protection limit for 12 AWG copper.2023 NEC §240.4(D)

The rating of a branch circuit supplying two or more outlets is determined by what?

• a.The largest conductor
• b.The voltage only
• c.The ampere rating of the overcurrent device protecting the circuit✓
• d.The receptacle count

Section 210.3 states that a branch circuit's rating is determined by the maximum permitted ampere rating of the overcurrent device protecting the circuit, using standard sizes such as 15, 20, 30, 40, and 50 A. The conductor size, number of receptacles, or voltage alone do not define the branch-circuit rating.2023 NEC §210.18

The working space required in front of electrical equipment must be kept clear and, in general, may be used for what purpose?

• a.No storage; it must remain clear for access✓
• b.Temporary parts staging
• c.Storage of conduit
• d.Mounting a subpanel

Section 110.26(B) requires the working space to be kept clear and prohibits using it for storage; when energized equipment needs servicing, the space must be clear. Using it for conduit storage, parts staging, or mounting another panel would obstruct required access to live parts.2023 NEC §110.26(B)

Couplings and connectors used with electrical metallic tubing (EMT) in a wet location must be what?

• a.Painted
• b.Set-screw type
• c.Listed for use in wet locations✓
• d.Threaded

Section 358.42 requires EMT couplings and connectors used in wet locations to be listed for wet locations, commonly the raintight compression type. Plain set-screw fittings are not raintight, threading does not apply to EMT couplings, and paint does not make a fitting suitable for wet locations.2023 NEC §358.42

An outlet box used as the sole support for a ceiling-suspended (paddle) fan must be what?

• a.A handy box
• b.Any 4-inch square box
• c.Listed and marked for that purpose✓
• d.A plastic device box

Section 314.27(C) requires an outlet box used as the sole support of a ceiling-suspended paddle fan to be listed and marked for that application, and to support the fan weight. A standard 4-in square box, a plastic device box, or a handy box not so listed cannot serve as the sole fan support.2023 NEC §314.27(C)

A 4" x 1-1/2" square box has a volume of 21.0 in³. With no clamps, devices, or other allowances, what is the maximum number of 14 AWG conductors permitted in the box?

• a.8
• b.11
• c.10✓
• d.9

Each 14 AWG conductor requires a 2.00 in³ volume allowance from Table 314.16(B). 21.0 ÷ 2.00 = 10.5, and you round down to 10 conductors. Rounding up to 11 would exceed the box volume, and 9 or 8 understates the count.2023 NEC §314.16(B)

Using the same 21.0 in³ box with no other fill allowances, what is the maximum number of 12 AWG conductors permitted?

• a.9✓
• b.10
• c.7
• d.8

Each 12 AWG conductor requires 2.25 in³ per Table 314.16(B). 21.0 ÷ 2.25 = 9.33, rounded down to 9 conductors. 10 would exceed the volume, and 8 or 7 undercounts.2023 NEC §314.16(B)

Per Table 314.16(B), what is the free-space volume allowance required for a single 12 AWG conductor?

• a.2.00 in³
• b.3.00 in³
• c.2.50 in³
• d.2.25 in³✓

Table 314.16(B) assigns 2.25 in³ per 12 AWG conductor. 2.00 in³ is the value for 14 AWG, 2.50 in³ is for 10 AWG, and 3.00 in³ is for 8 AWG.2023 NEC §314.16(B)

In a box-fill calculation, a single device (a receptacle or switch mounted on a yoke or strap) counts as how many conductor volume allowances?

• a.3
• b.1
• c.2✓
• d.0

Per 314.16(B)(4), each yoke or strap containing one or more devices counts as two volume allowances, based on the largest conductor connected to the device. Counting it as 1 or 0 understates the fill; a standard single device is not 3.2023 NEC §314.16(B)(4)

A box contains three internal cable clamps. In the box-fill calculation, how many volume allowances do the clamps require in total?

• a.0 (clamps are exempt)
• b.3 (one per clamp)
• c.1 (a single allowance)✓
• d.6 (two per clamp)

Per 314.16(B)(2), where one or more internal clamps are present, a single volume allowance is required based on the largest conductor in the box — not one per clamp. So three clamps still count as only one allowance.2023 NEC §314.16(B)(2)

A box has four 12 AWG equipment grounding conductors entering it. How are they counted in the box-fill calculation?

• a.Each counts individually (four allowances)
• b.They are never counted
• c.They count as two allowances
• d.All together count as a single volume allowance✓

Per 314.16(B)(5), all equipment grounding conductors together count as a single volume allowance, based on the largest EGC present. Counting them individually overstates the fill, and they are not exempt from the calculation.2023 NEC §314.16(B)(5)

A box contains five 12 AWG current-carrying conductors, one 12 AWG equipment grounding conductor, one internal cable clamp, and one switch on a yoke (all conductors 12 AWG). What total box volume is required?

• a.22.50 in³
• b.18.00 in³
• c.20.25 in³✓
• d.15.75 in³

At 2.25 in³ each: five conductors = 11.25, EGCs (as one) = 2.25, clamp (as one) = 2.25, and the yoke = 2 × 2.25 = 4.50. Total = 11.25 + 2.25 + 2.25 + 4.50 = 20.25 in³. The other values omit one or more required allowances.2023 NEC §314.16(B)

A single unbroken conductor passes straight through a box without being spliced or terminated. For box fill, it is counted as how many conductors?

• a.One-half
• b.One✓
• c.Two
• d.Zero

Per 314.16(B)(1), each conductor that runs through the box without splice or termination is counted once. It is not exempt (zero) and not doubled; a conductor is only counted twice when it is looped unbroken with a length of at least twice the minimum required for free conductors.2023 NEC §314.16(B)(1)

How are conductors that both originate and terminate within the box (such as short pigtails or jumpers) treated in a box-fill calculation?

• a.They are not counted✓
• b.They count as clamp allowances
• c.They count as one each
• d.They count as two each

Per 314.16(B)(1), a conductor that originates and terminates within the box, such as a pigtail, is not counted in the box fill. Only conductors that enter and are not spliced (or that terminate on a device) get an allowance.2023 NEC §314.16(B)(1)

Per Chapter 9, Table 1, what is the maximum permitted conduit fill percentage when three or more conductors are installed in a raceway?

• a.60%
• b.53%
• c.31%
• d.40%✓

Chapter 9, Table 1 limits fill to 40% for three or more conductors. 53% is the limit for a single conductor, 31% is for exactly two conductors, and 60% is not a code fill value.2023 NEC Chapter 9, Table 1

Per Chapter 9, Table 1, what is the maximum permitted fill percentage when exactly two conductors are installed in a conduit?

• a.31%✓
• b.25%
• c.53%
• d.40%

Table 1 sets a 31% fill limit for exactly two conductors, reflecting the jamming ratio concern. 40% applies to three or more, 53% to a single conductor, and 25% is not used.2023 NEC Chapter 9, Table 1

Per Chapter 9, Table 1, what is the maximum permitted fill percentage when only one conductor is installed in a conduit?

• a.31%
• b.60%
• c.53%✓
• d.40%

A single conductor may fill up to 53% of the conduit's internal area per Table 1. 31% is for two conductors, 40% for three or more, and 60% is not a code value.2023 NEC Chapter 9, Table 1

Per Annex C, Table C.1, what is the maximum number of 12 AWG THHN conductors permitted in 1/2" EMT?

• a.7
• b.12
• c.9✓
• d.5

Table C.1 lists 9 for 12 AWG THHN in 1/2" EMT. 12 is the count for 14 AWG, 5 is for 10 AWG, and 7 is not a listed value.2023 NEC Annex C, Table C.1

Per Annex C, Table C.1, what is the maximum number of 14 AWG THHN conductors permitted in 1/2" EMT?

• a.12✓
• b.15
• c.9
• d.10

Table C.1 lists 12 for 14 AWG THHN in 1/2" EMT. 9 is the count for 12 AWG, and 10 or 15 are not listed values for this size.2023 NEC Annex C, Table C.1

Per Annex C, Table C.1, what is the maximum number of 12 AWG THHN conductors permitted in 3/4" EMT?

• a.16✓
• b.9
• c.12
• d.22

Table C.1 lists 16 for 12 AWG THHN in 3/4" EMT. 22 is the count for 14 AWG in 3/4" EMT, and 9 is the count for 12 AWG in the smaller 1/2" EMT.2023 NEC Annex C, Table C.1

Per Annex C, Table C.1, what is the maximum number of 10 AWG THHN conductors permitted in 1/2" EMT?

• a.9
• b.7
• c.5✓
• d.3

Table C.1 lists 5 for 10 AWG THHN in 1/2" EMT. 9 is the value for 12 AWG, 3 is the value for 8 AWG, and 7 is not listed for this size.2023 NEC Annex C, Table C.1

The internal cross-sectional area of 1/2" EMT is 0.304 in³ per Table 4. For three or more conductors, what usable fill area (40%) is available?

• a.0.161 in²
• b.0.122 in²✓
• c.0.094 in²
• d.0.304 in²

0.304 × 0.40 = 0.122 in². The 31% (two-conductor) area would be 0.094 in² and the 53% (single-conductor) area would be 0.161 in²; 0.304 is the full 100% area.2023 NEC Chapter 9, Table 4

The internal area of 3/4" EMT is 0.533 in² per Table 4. What is the 40% usable fill area for three or more conductors?

• a.0.213 in²✓
• b.0.165 in²
• c.0.283 in²
• d.0.122 in²

0.533 × 0.40 = 0.213 in². The 31% area is 0.165 in² and the 53% area is 0.283 in²; 0.122 in² is the 40% area of the smaller 1/2" EMT.2023 NEC Chapter 9, Table 4

Given a 40% usable fill area of 0.213 in² (3/4" EMT) and a 12 AWG THHN cross-sectional area of 0.0133 in² (Table 5), how many 12 AWG THHN conductors fit?

• a.22
• b.16✓
• c.9
• d.12

0.213 ÷ 0.0133 = 16.0, so 16 conductors fit — matching Annex C. 9 corresponds to 1/2" EMT, 22 is the 14 AWG count for 3/4", and 12 is not correct here.2023 NEC Chapter 9, Table 4

Six current-carrying 12 AWG THHN conductors (90°C, 30 A base) share a raceway. Applying only the adjustment factor for 4–6 conductors, what is the adjusted ampacity?

• a.21 A
• b.30 A
• c.24 A✓
• d.27 A

The adjustment factor for 4–6 current-carrying conductors is 80%. 30 A × 0.80 = 24 A. 70% (21 A) applies to 7–9 conductors, and 30 A ignores the required adjustment.2023 NEC §310.15(C)(1)