BRAIN BUSTERS

25 Brain Buster Questions

Ready to test yourself?

Work through all 25 questions before checking the Explanation Key.

Choose the answer you believe is correct. Use the hint if you need it, but try to solve the problem yourself first.

Based on the 2026 NEC.

⚡ 2026 NEC Brain Busters ⚡

25 Brain Buster Questions

Ready to test yourself?

Work through all 25 questions before checking the Explanation Key.

Choose the answer you believe is correct. Use the hint if you need it, but try to solve the problem yourself first.

Based on the 2026 NEC.

⚡ Brain Buster #1 ⚡

A 1200-ampere electrical service is supplied by three 600 kcmil THWN conductors in parallel per phase.

What size main bonding jumper is required for the service?

A. 250 kcmil Cu
B. 4/0 AWG Cu
C. 2/0 AWG Cu
D. 1/0 AWG Cu

💡 Hint: For parallel service conductors, determine the equivalent area first. If that equivalent area exceeds the table range, look for the rule that follows the table.

⚡ Brain Buster #2 ⚡

A multifamily dwelling project contains four dwelling units and is being calculated using the standard method.

According to the applicable dwelling-unit demand factor, what percentage is applied to the portion of the general lighting, small-appliance, and laundry load remaining after the first 3,000 VA?

A. 35%
B. 50%
C. 43%
D. 45%

💡 Hint: Look at the dwelling-unit demand factors rather than trying to invent a percentage from the number of units.

⚡ Brain Buster #3 ⚡

An electrician needs to install the following copper THHN/THWN-2 conductors in one raceway:

- 8 × #2 AWG

- 12 × #6 AWG

- 10 × #10 AWG

No equipment grounding conductor is included, and the raceway is RMC.

What is the minimum RMC trade size required?

A. 3 in.
B. 2½ in.
C. 3½ in.
D. 3¼ in.

💡 Hint: This is a mixed-conductor raceway-fill problem. Don't try to use one conductor size for the entire calculation.

⚡ Brain Buster #4 ⚡

A box with a flush-type cover is recessed in a noncombustible surface.

What is the maximum permitted gap at the edge of the box before the gap must be repaired?

A. 1/16 in.
B. 1/8 in.
C. 1/4 in.
D. 1/2 in.

💡 Hint: The question asks for the maximum gap at the edge, not the permitted recess depth.

⚡ Brain Buster #5 ⚡

A pool pump motor is supplied directly by a branch circuit and is hardwired rather than connected by a receptacle.

Is GFCI protection still required for the pool pump motor circuit?

A. Yes, GFCI protection is required whether the pump is cord-and-plug connected or hardwired.
B. No, GFCI protection is required only when a receptacle is used.
C. No, hardwired pool motors are exempt from GFCI requirements.
D. Yes, but only when the motor is within 6 ft of the pool.

💡 Hint: Don't let the word "receptacle" make you overlook what the GFCI requirement is actually protecting.

⚡ Brain Buster #6 ⚡

A cable tray contains 600-volt-rated MC cable and medium-voltage cable rated over 1,000 volts.

Is a physical barrier automatically required between the two types of cable?

A. Yes, a barrier is always required between all voltage classes.
B. No, the 600-volt-rated MC cable may be installed with the medium-voltage cable without a barrier under the applicable NEC conditions.
C. Yes, unless both cables have the same conductor size.
D. No, because cable tray installations never require separation.

💡 Hint: Pay very close attention to the fact that the MC cable is specifically stated to be 600V rated and to the voltage rating of the other cable.

⚡ Brain Buster #7 ⚡

A tray cable is intended to leave the cable tray and make an exposed run to utilization equipment.

Which designation is important for this type of exposed run?

A. Type NM
B. Type SE
C. Type TC-ER
D. Type UF

💡 Hint: Think about the "-ER" designation and UL 1277.

⚡ Brain Buster #8 ⚡

A 480-volt motor has its frame connected to the branch-circuit equipment grounding conductor. The installer also connects the motor frame to an equipotential bonding grid.

Which statement is most accurate?

A. The additional bonding connection is prohibited because it creates circulating current.
B. The additional bonding connection may be permitted, but it does not replace the required equipment grounding conductor.
C. The connection is permitted only when the motor is GFCI protected.
D. The motor frame may be connected to the bonding grid instead of the equipment grounding conductor.

💡 Hint: Separate the purpose of the required EGC from supplemental bonding.

⚡ Brain Buster #9 ⚡

A single-family dwelling has 2,000 square feet of floor area.

Using the 2026 NEC standard method, calculate the dwelling's general load consisting of:

- General lighting

- Two required small-appliance branch circuits

- One laundry circuit

What is the calculated demand load?

A. 4,925 VA
B. 5,250 VA
C. 6,300 VA
D. 8,500 VA

💡 Hint: Use the 2026 dwelling general-lighting value, add the required 1,500-VA loads, and then apply the applicable demand factor.

⚡ Brain Buster #10 ⚡

A single-phase, 240-volt motor has a table full-load current of 28 amperes. It is protected by an inverse-time circuit breaker for branch-circuit short-circuit and ground-fault protection.

Assuming the calculated breaker size allows the motor to start, what is the maximum standard breaker size permitted?

A. 40 A
B. 50 A
C. 60 A
D. 70 A

💡 Hint: Start with Table 430.52 and the percentage permitted for an inverse-time circuit breaker.

⚡ Brain Buster #11 ⚡

A dwelling-unit kitchen has the two required 20-ampere small-appliance branch circuits.

A 1,200-watt cord-and-plug-connected countertop microwave is plugged into one of those circuits.

The appliance listing and manufacturer's instructions do not require an individual branch circuit.

Does the 2026 NEC require this microwave to have an individual branch circuit?

A. Yes. All microwaves require an individual branch circuit.
B. Yes. Any cord-and-plug appliance over 1,000 watts requires an individual circuit.
C. No. It may be supplied by a required 20-ampere small-appliance branch circuit unless another NEC requirement or the manufacturer's instructions require an individual circuit.
D. Yes. Small-appliance branch circuits may supply only countertop receptacles and nothing else.

💡 Hint: The NEC does not create a blanket "over 1,000 watts = dedicated circuit" rule.

⚡ Brain Buster #12 ⚡

A dwelling-unit garage has a 125-volt, 20-ampere receptacle installed in the ceiling to supply a garage door opener.

Is GFCI protection required?

A. Yes, because the receptacle is a 125-volt, 15- or 20-ampere receptacle in a garage.
B. No, because the receptacle is mounted on the ceiling.
C. No, because it supplies a dedicated garage door opener.
D. Only if the receptacle is within 6 ft of a sink.

💡 Hint: The location of the receptacle matters more than the fact that it supplies a garage door opener.

⚡ Brain Buster #13 ⚡

The following conductors are installed in one RMC raceway:

- 12 ungrounded #12 AWG THHN copper conductors

- 1 grounded #12 AWG conductor

- 1 equipment grounding conductor

The ambient temperature is 87°F.

What is the minimum RMC trade size identified by the applicable calculation?

A. ½ in.
B. ¾ in.
C. 1 in.
D. 1¼ in.

💡 Hint: Don't stop at raceway fill. The conductor count also raises an ampacity-adjustment question.

⚡ Brain Buster #14 ⚡

A 120/240-volt, single-phase dwelling service is being calculated using the 2026 NEC.

The dwelling general load consists of:

- General lighting = 3,000 VA

- Three small-appliance circuits = 3 × 1,500 VA

- One laundry circuit = 1,500 VA

- Dryer = 5,000 VA

- Range = 8,000 VA

Using the applicable standard-method demand factors, what is the minimum calculated service load before converting to amperes?

A. 16,500 VA
B. 18,500 VA
C. 20,000 VA
D. 23,000 VA

💡 Hint: Apply the dwelling demand factor to the general load first. Then handle the dryer and range according to their applicable rules.

⚡ Brain Buster #15 ⚡

A feeder supplies two motor-operated loads:

- 30 A air compressor

- 24 A dust collector

The equipment is listed and designed so only one load can operate at a time.

According to the 2026 NEC, what is the minimum calculated load for this feeder?

A. 30 A
B. 37.5 A
C. 54 A
D. 67.5 A

💡 Hint: First recognize that the loads are noncoincident. Then determine how the motor load is treated under the applicable motor rule.

⚡ Brain Buster #16 ⚡

A 120/240-volt dwelling service uses two 8-ft ground rods driven 6 ft apart. A grounding electrode conductor runs from the service equipment to the first rod and then to the second rod.

The measured resistance of the first rod to earth is 38 ohms.

According to the applicable grounding-electrode requirements, what is required?

A. No additional action is required because two rods are already installed.
B. A supplemental grounding electrode is required because the resistance exceeds 25 ohms.
C. The rods must be replaced because ground rods cannot be installed in pairs.
D. The grounding electrode conductor must be increased to reduce the rod resistance.

💡 Hint: Pay attention to the rule concerning a single rod's resistance to earth and the exception involving the installation of a second electrode.

⚡ Brain Buster #17 ⚡

A restaurant feeder supplies the following kitchen equipment:

- Electric range

- Deep fryer

- Ice machine

- Dishwasher

Under 2026 NEC Article 120.56, which statement is most accurate concerning commercial kitchen demand factors?

A. Only electric cooking appliances qualify.
B. Only cooking appliances and dishwashers qualify.
C. The ice machine and dishwasher are automatically excluded.
D. None of the listed items is automatically excluded solely by its name; the applicable requirements of 120.56 determine what qualifying kitchen equipment may be included.

💡 Hint: Don't answer based only on the equipment's name. The important phrase is the Code's treatment of qualifying kitchen equipment.

⚡ Brain Buster #18 ⚡

A restaurant has the following kitchen equipment connected to a feeder:

- Electric range = 12 kW

- Deep fryer = 8 kW

- Griddle = 10 kW

- Convection oven = 15 kW

Using the applicable 2026 NEC commercial kitchen demand factors, what is the calculated demand load?

A. 33.75 kW
B. 36.00 kW
C. 40.50 kW
D. 45.00 kW

💡 Hint: Don't simply total the nameplate ratings. Determine the applicable commercial-kitchen demand factor.

⚡ Brain Buster #19 ⚡

A hermetic refrigerant motor-compressor has a nameplate-rated load current and/or branch-circuit selection current marked on its nameplate.

When determining the ampere rating of the hermetic refrigerant motor-compressor itself, which percentage is required to be applied to the nameplate current or branch-circuit selection current?

A. 125%
B. 150%
C. 110%
D. 100%

💡 Hint: Be careful about what the question is asking. Don't automatically apply the 125% rule used for branch-circuit conductor sizing.

⚡ Brain Buster #20 ⚡

A 5 HP, 230-volt, single-phase motor is rated for continuous duty and has a service factor of 1.15. The motor nameplate indicates a full-load current of 22 amperes.

The branch-circuit conductors are copper THHN, and the terminals are rated 75°C.

What are the minimum branch-circuit conductor size and maximum initial overload setting permitted under 430.32(A)(1)?

A. #12 AWG Cu THHN and 25.3 A
B. #10 AWG Cu THHN and 27.5 A
C. #10 AWG Cu THHN and 35 A
D. #8 AWG Cu THHN and 27.5 A

💡 Hint: Don't use the motor nameplate current alone to size the branch-circuit conductors.

⚡ Brain Buster #21 ⚡

The 2026 NEC recognizes 10-ampere branch circuits.

Which application is permitted under the specific 2026 branch-circuit rules?

A. General-purpose receptacle outlets throughout a dwelling
B. Any receptacle circuit where the calculated load is less than 10 amperes
C. Lighting outlets and certain dwelling-unit exhaust fans installed on bathroom or laundry-room lighting circuits
D. Any circuit supplying LED lighting and receptacle outlets

💡 Hint: The 2026 change is intentionally narrow. A 10-ampere circuit is not a replacement for an ordinary 15- or 20-ampere general-purpose branch circuit.

⚡ Brain Buster #22 ⚡

An electrical conductor has been subjected to severe overheating. Inspection determines that the conductor insulation has actually been damaged.

An electrician proposes wrapping the damaged area with electrical tape and returning the conductor to service.

According to the 2026 NEC provisions concerning damaged wiring methods and conductors, which statement is correct?

A. The conductor may remain in service if the tape restores the insulation thickness.
B. The conductor may remain in service if a GFCI protects the circuit.
C. The conductor is considered no longer suitable for continued use and must be replaced.
D. The conductor may remain in service if less than 6 inches of insulation is damaged.

💡 Hint: The key distinction is between a superficial mark and actual damage.

⚡ Brain Buster #23 ⚡

A single-family dwelling has 2,400 square feet of floor area, calculated from the outside dimensions and excluding open porches, garages, and unfinished spaces.

Under the 2026 NEC, which pair of values is correct when determining the minimum number of branch circuits and when performing the standard feeder/service load calculation?

A. 2 VA/ft² for both
B. 3 VA/ft² for both
C. 2 VA/ft² for branch circuits and 3 VA/ft² for feeder/service
D. 3 VA/ft² for branch circuits and 2 VA/ft² for feeder/service

💡 Hint: The 2026 NEC did not eliminate the 3 VA/ft² value. Ask yourself what calculation you're performing.

⚡ Brain Buster #24 ⚡

An electrician is installing raceways or cable assemblies above a suspended ceiling.

The electrician proposes attaching the wiring directly to the existing wires that support the suspended-ceiling grid.

According to the 2026 NEC, which statement is correct?

A. The wiring may be attached if it is lightweight.
B. The wiring may be attached if the ceiling-support wires are secured at both ends.
C. Wiring cannot be secured to or supported by the ceiling grid system or its support wires, although independent support wires may be permitted when installed in accordance with the NEC.
D. Wiring above a suspended ceiling must always be supported exclusively by threaded rod connected directly to the building structure.

💡 Hint: Don't confuse the ceiling-grid support wires with properly installed independent support wires.

⚡ Brain Buster #25 ⚡

A 2026 NEC exam question gives you a large amount of information about an electrical installation, including conductor types, equipment ratings, environmental conditions, and installation details.

After reading the question carefully, you determine that only one of those facts is actually necessary to answer the question being asked.

What is the best exam-preparation approach?

A. Use every fact provided because exam questions never include unnecessary information.
B. Memorize the answer from a previous practice test rather than rechecking the NEC.
C. Identify exactly what the question is asking, determine the minimum Code requirement, and eliminate information that is irrelevant to the question.
D. Choose the answer with the largest numerical value because exam questions usually favor the most conservative option.

💡 Hint: This is the "misdirection" trap. Read, dissect, verify. Don't let extra information pull you away from the actual question.

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⚠️ Educational Disclaimer

These Brainbusters are provided for educational and study purposes only and are based on the 2026 edition of the National Electrical Code (NEC).

Code requirements can vary based on the edition adopted by your jurisdiction, local amendments, and the specific installation. Always verify the applicable NEC requirements and local regulations before applying any information to an actual installation.

These Brainbusters are not a substitute for the NEC, professional judgment, or requirements enforced by the local Authority Having Jurisdiction (AHJ).

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