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MT Journeyman Electrician practice questions

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Question 1General Electrical Knowledge and Theory

A 240-volt single-phase branch circuit supplies a resistive load drawing 30 amperes. What is the power consumed by the load?

  1. 4,800 watts
  2. 8,000 watts
  3. 7,200 watts Correct answer.
  4. 1,200 watts

Explanation

For a purely resistive single-phase load, power equals voltage multiplied by current, so 240 V × 30 A = 7,200 W. No power factor adjustment is needed because the load is resistive.

Question 2General Electrical Knowledge and Theory

Which conductor property is the primary reason copper is preferred over aluminum for most branch-circuit wiring?

  1. Greater resistance per circular mil
  2. Lower cost per pound
  3. Lower melting temperature
  4. Higher conductivity per unit cross-section Correct answer.

Explanation

Copper has lower resistivity than aluminum, so a given cross-section carries current with less voltage drop and less heating. Aluminum's higher resistance per circular mil requires larger conductors for an equivalent ampacity.

Question 3General Electrical Knowledge and Theory

In a series circuit containing three resistors, which quantity is the same through every component?

  1. Voltage
  2. Power
  3. Current Correct answer.
  4. Resistance

Explanation

A series circuit provides only one path for electron flow, so the same current passes through each element. Voltage, power, and resistance may differ from one component to the next depending on their values.

Question 4General Electrical Knowledge and Theory

What is the opposition to a change in current flow offered by a coil called?

  1. Impedance
  2. Capacitive reactance
  3. Inductive reactance Correct answer.
  4. Conductance

Explanation

Inductive reactance is the opposition a coil presents to alternating current, equal to 2πfL, and it increases with frequency. It arises because the changing magnetic field induces a counter-voltage that opposes the change in current.

Question 5General Electrical Knowledge and Theory

Which of the following best describes the function of a bonding jumper in an electrical system?

  1. It provides overcurrent protection for the circuit conductors
  2. It ensures electrical continuity between metal parts that must be at the same potential Correct answer.
  3. It limits the voltage on the service conductors during a surge
  4. It carries the normal return current from the load back to the source

Explanation

A bonding jumper connects metal parts to establish electrical continuity and equalize potential, which lets fault current return to the source and trip the overcurrent device. It is not intended to serve as a normal current-carrying conductor.

Question 6General Electrical Knowledge and Theory

A circuit has a resistance of 12 ohms and a current of 5 amperes. What voltage is applied?

  1. 0.42 volts
  2. 2.4 volts
  3. 60 volts Correct answer.
  4. 17 volts

Explanation

Ohm's law states that voltage equals current times resistance, so 5 A × 12 Ω = 60 V. This is a direct application of E = I × R.

Question 7General Electrical Knowledge and Theory

In a parallel circuit with two resistors of unequal value connected across a constant voltage source, how does the current divide between them?

  1. Both resistors carry equal current
  2. The smaller resistor carries the larger current Correct answer.
  3. The larger resistor carries the larger current
  4. The current divides equally only if the resistors are inductive

Explanation

Each parallel branch sees the full source voltage, so current in each branch equals voltage divided by that branch's resistance. The lower-resistance branch therefore draws the greater current.

Question 8General Electrical Knowledge and Theory

A coil has an inductance of 0.2 henry and is connected to a 60-hertz source. What is its inductive reactance?

  1. Approximately 12 ohms
  2. Approximately 0.2 ohms
  3. Approximately 75 ohms Correct answer.
  4. Approximately 377 ohms

Explanation

Inductive reactance equals 2πfL, so 2 × 3.1416 × 60 × 0.2 ≈ 75.4 Ω. The frequency and inductance are multiplied together after applying the 2π constant.

Question 9General Electrical Knowledge and Theory

A 120-volt circuit carries a load of 20 amperes with a power factor of 0.8. What is the true power delivered?

  1. 3,000 watts
  2. 1,920 watts Correct answer.
  3. 1,500 watts
  4. 2,400 watts

Explanation

True power equals voltage times current times power factor, so 120 V × 20 A × 0.8 = 1,920 W. Apparent power would be 2,400 VA before the power factor correction.

Question 10General Electrical Knowledge and Theory

Which condition produces the greatest heating in a conductor of fixed resistance?

  1. High current flowing for a long time Correct answer.
  2. Low current flowing briefly
  3. High voltage with no current
  4. Low voltage with high resistance and no current

Explanation

Heat generated in a conductor follows I²R, so heating rises with the square of current and accumulates over time. Doubling current quadruples the heating for the same resistance.

Question 11General Electrical Knowledge and Theory

What happens to the total capacitance when two capacitors are connected in series?

  1. It equals the average of the two capacitances
  2. It becomes zero regardless of the values
  3. It is the sum of the individual capacitances
  4. It is less than the smallest individual capacitance Correct answer.

Explanation

Series capacitors combine like parallel resistors, so the reciprocal of total capacitance is the sum of the reciprocals. The result is always smaller than the smallest capacitor in the string.

Question 12General Electrical Knowledge and Theory

A three-phase, 480-volt motor draws 25 amperes per phase at unity power factor. What is the approximate input power?

  1. About 36 kilowatts
  2. About 20.8 kilowatts Correct answer.
  3. About 12 kilowatts
  4. About 60 kilowatts

Explanation

Three-phase power equals √3 × line voltage × line current × power factor, so 1.732 × 480 × 25 × 1.0 ≈ 20,784 W. At unity power factor no further correction is required.

Question 13General Electrical Knowledge and Theory

In a wye-connected three-phase system, what is the relationship between line voltage and phase voltage?

  1. Line voltage equals phase voltage divided by √3
  2. Line voltage equals phase voltage
  3. Line voltage equals phase voltage multiplied by 3
  4. Line voltage equals phase voltage multiplied by √3 Correct answer.

Explanation

In a wye connection, each phase winding connects between a line and the neutral, so line voltage spans two windings displaced by 120 degrees. Vector addition gives a line voltage of √3 times the phase voltage.

Question 14General Electrical Knowledge and Theory

Why does skin effect become significant in large conductors carrying alternating current?

  1. Current tends to concentrate near the conductor surface as frequency rises Correct answer.
  2. Magnetic fields cancel entirely inside the conductor at all frequencies
  3. The conductor's resistance decreases as frequency rises
  4. Electrons are repelled by the insulation at high frequency

Explanation

Alternating magnetic fields inside the conductor induce eddy currents that oppose current flow in the center and reinforce it near the surface. The result is a higher effective resistance at higher frequencies and in larger conductors.

Question 15General Electrical Knowledge and Theory

A conductor with a resistance of 0.5 ohm carries 40 amperes. What is the voltage drop along the conductor?

  1. 0.0125 volts
  2. 40.5 volts
  3. 80 volts
  4. 20 volts Correct answer.

Explanation

Voltage drop equals current times resistance, so 40 A × 0.5 Ω = 20 V. This drop reduces the voltage available at the load end of the circuit.

Question 16General Electrical Knowledge and Theory

A 10-horsepower, 240-volt single-phase motor has an efficiency of 85 percent and a power factor of 0.9. What is the approximate line current?

  1. About 40 amperes Correct answer.
  2. About 27 amperes
  3. About 48 amperes
  4. About 34 amperes

Explanation

Output of 10 hp equals 7,460 W, so input power is 7,460 ÷ 0.85 ≈ 8,776 W. Line current is input power divided by (voltage × power factor), giving about 40.6 A.

Question 17General Electrical Knowledge and Theory

In an AC circuit containing both resistance and inductive reactance, how is impedance calculated?

  1. The square root of the sum of the squares of resistance and reactance Correct answer.
  2. The difference between reactance and resistance
  3. The arithmetic sum of resistance and reactance
  4. The product of resistance and reactance

Explanation

Resistance and reactance are 90 degrees out of phase, so they combine as perpendicular vectors. Impedance is therefore the square root of R² plus X², not a simple arithmetic sum.

Question 18General Electrical Knowledge and Theory

A transformer has 480 turns on the primary and 120 turns on the secondary. If the primary is supplied at 240 volts, what is the secondary voltage?

  1. 960 volts
  2. 120 volts
  3. 60 volts Correct answer.
  4. 240 volts

Explanation

The turns ratio is 480 to 120, or 4 to 1, and voltage transforms in the same proportion. Dividing 240 V by 4 gives 60 V on the secondary.

Question 19General Electrical Knowledge and Theory

A 20-ampere continuous load is supplied by a branch circuit. Applying the standard 125 percent continuous-load factor, what minimum circuit ampacity is required?

  1. 24 amperes
  2. 16 amperes
  3. 20 amperes
  4. 25 amperes Correct answer.

Explanation

Continuous loads are sized at 125 percent of the load current to account for sustained operation and heat buildup. Multiplying 20 A by 1.25 gives 25 A minimum circuit ampacity.

Question 20General Electrical Knowledge and Theory

Why is the neutral conductor in a balanced three-phase wye system able to be smaller than the phase conductors under some conditions?

  1. The phase currents add in the neutral, but at a lower frequency
  2. The neutral is bonded to earth and returns current through the ground
  3. The phase currents partially cancel, leaving little current in the neutral Correct answer.
  4. The neutral carries no voltage and therefore no energy

Explanation

In a balanced wye system the three phase currents are equal in magnitude and 120 degrees apart, so their vector sum in the neutral is essentially zero. The neutral therefore carries only the imbalance among phases.

Question 21Wiring Methods and Materials

A rigid metal conduit run is being installed in an area subject to physical damage. Which wiring method provides the required mechanical protection for the conductors?

  1. Electrical nonmetallic tubing
  2. Surface metal raceway
  3. Armored cable
  4. Rigid metal conduit Correct answer.

Explanation

Rigid metal conduit is recognized as a wiring method that supplies substantial mechanical protection and is permitted in locations subject to severe physical damage. Nonmetallic tubing and armored cable offer far less resistance to impact and abrasion. Surface raceway is intended for exposed surface wiring and is not the standard choice where heavy abuse is expected.

Question 22Wiring Methods and Materials

When supporting Type NM cable, what is the maximum permitted spacing between supports for a horizontal run?

  1. 12 feet
  2. 6 feet
  3. 3 feet
  4. 4.5 feet Correct answer.

Explanation

Nonmetallic-sheathed cable must be secured in place at intervals not exceeding 4.5 feet and within 12 inches of every box or fitting. This spacing keeps the cable from sagging and limits strain on terminations. Larger spacings apply to some raceways, not to NM cable.

Question 23Wiring Methods and Materials

A conduit body is installed in a straight run of rigid conduit where the conductors pass through without being pulled at that point. What minimum marking must the conduit body bear to be used in this manner?

  1. A marking of the conduit trade size Correct answer.
  2. A volume marking only
  3. A marking of the maximum number of conductors
  4. A cubic-inch capacity marking

Explanation

A conduit body used as a pull point or in a straight run must be durably and legibly marked with its volume or with the trade size of the conduit it connects. The trade-size marking is the standard identification for straight-through use. Conductors are then limited by the cross-sectional fill rules tied to that size.

Question 24Wiring Methods and Materials

Which of the following is a recognized use of liquidtight flexible metal conduit?

  1. Use as a grounding electrode conductor
  2. Connection of motors and equipment where flexibility is needed and moisture is present Correct answer.
  3. Support of luminaires over 50 pounds
  4. Direct burial without supplementary protection

Explanation

Liquidtight flexible metal conduit is intended for wet, damp, or oily locations where flexibility is needed, such as motor terminations and vibrating equipment. It is not a general substitute for rigid conduit in every location. Direct burial and grounding-electrode uses require specific conditions or other methods.

Question 25Wiring Methods and Materials

A box is installed in a wall with a combustible finish. What is the minimum required extension of a nonmetallic box beyond the finished surface?

  1. The box must be flush with or extend beyond the finished surface. Correct answer.
  2. The box may be recessed up to 1/2 inch.
  3. The box may be recessed up to 1/4 inch.
  4. The box must extend at least 1 inch beyond the surface.

Explanation

In walls with combustible finishes, boxes must be installed so the front edge is flush with or projects beyond the finished surface. This prevents the combustible finish from being exposed to heat or arcing at the box opening. Recessing is only allowed in specific noncombustible conditions.

Question 26Wiring Methods and Materials

Which conductor material is permitted for use as an equipment grounding conductor in a rigid metal conduit installation?

  1. A white insulated conductor
  2. A bare copper conductor sized per the equipment grounding table Correct answer.
  3. The rigid metal conduit itself
  4. A green-and-yellow striped conductor only

Explanation

Equipment grounding conductors must be sized using the equipment grounding conductor table based on the overcurrent device rating. Rigid metal conduit may serve as an equipment grounding conductor only where permitted and where continuity is assured. A correctly sized copper conductor is always acceptable.

Question 27Wiring Methods and Materials

Type MC cable is being installed in a commercial building. Which condition is required for the cable to be used without an additional equipment grounding conductor?

  1. The cable must contain a green insulated conductor.
  2. The cable must have an overall nonmetallic jacket.
  3. The cable must be installed in conduit.
  4. The cable must have an interlocking metal tape armor listed as an equipment grounding means. Correct answer.

Explanation

Metal-clad cable may use its interlocking armor as an equipment grounding conductor only where the armor is listed and identified for that purpose. Otherwise a separate grounding conductor must be included. The armor must provide a low-impedance path for fault current.

Question 28Wiring Methods and Materials

What is the minimum size of rigid metal conduit permitted for general wiring installations?

  1. 1-1/4 inch trade size
  2. 1/2 inch trade size Correct answer.
  3. 1 inch trade size
  4. 3/4 inch trade size

Explanation

The smallest trade size of rigid metal conduit recognized for general use is 1/2 inch. Smaller sizes are not standard for power and lighting circuits. Larger minimums may be required by local amendments or specific applications.

Question 29Wiring Methods and Materials

A junction box contains four 12 AWG conductors and two 14 AWG conductors, all with splices. Using the standard box-fill method, what is the minimum box volume required?

  1. 22 cubic inches
  2. 18 cubic inches Correct answer.
  3. 14 cubic inches
  4. 26 cubic inches

Explanation

Each 12 AWG conductor counts as 2.25 cubic inches and each 14 AWG conductor as 2.0 cubic inches. Four 12 AWG conductors require 9 cubic inches and two 14 AWG conductors require 4 cubic inches, for 13 cubic inches. Adding the required allowance for the largest conductor and a device or clamp yields a minimum near 18 cubic inches.

Question 30Wiring Methods and Materials

Which wiring method is permitted in a Class I, Division 1 hazardous location for a circuit supplying a motor?

  1. Electrical nonmetallic tubing
  2. Type NM cable
  3. Surface metal raceway
  4. Rigid metal conduit with threaded joints Correct answer.

Explanation

In Class I, Division 1 locations, threaded rigid metal conduit is a standard recognized wiring method because it contains explosions and prevents flame propagation. Nonmetallic and surface raceway methods lack the required integrity. Flexible connections are permitted only in specific, limited situations.

Question 31Wiring Methods and Materials

What is the maximum permitted fill of a conduit for a run containing three or more conductors?

  1. 40 percent Correct answer.
  2. 53 percent
  3. 31 percent
  4. 25 percent

Explanation

For three or more conductors in a raceway, the total cross-sectional area of the conductors may not exceed 40 percent of the conduit interior area. This allows room for pulling and heat dissipation. Higher percentages apply only to one or two conductors.

Question 32Wiring Methods and Materials

A rigid nonmetallic conduit is installed outdoors where the ambient temperature may reach 120°F. What adjustment applies to the conduit fill or support?

  1. The conduit must be painted white.
  2. The conduit must be converted to metal.
  3. No adjustment is needed for temperature.
  4. The support spacing must be reduced because the conduit expands and softens. Correct answer.

Explanation

Rigid nonmetallic conduit is subject to expansion and to softening at elevated temperatures, so support spacing is reduced and expansion fittings are used. The material's strength decreases as temperature rises. Painting or converting to metal is not a code requirement.

Question 33Wiring Methods and Materials

Which of the following is required when Type AC cable passes through a stud or joist?

  1. A grounding conductor
  2. A conduit sleeve for the entire run
  3. A junction box at every stud
  4. A protective bushing or plate where the cable is within 1-1/4 inches of the edge Correct answer.

Explanation

Where cable is installed through bored holes in wood members, protection is required when the hole is within 1-1/4 inches of the nearest edge of the member. A steel plate or bushing prevents nails and screws from damaging the cable. This protection applies to both NM and AC cable.

Question 34Wiring Methods and Materials

A straight pull of four 4/0 AWG conductors is made through a 3-inch rigid metal conduit. What is the minimum bending radius most directly controlled by?

  1. The type of insulation color
  2. The length of the pull
  3. The conduit trade size only
  4. The diameter of the largest conductor and the number of conductors Correct answer.

Explanation

Conduit bends must have a radius large enough to prevent damage to the conductors during pulling. The controlling factors are the conductor diameter and the number of conductors in the run. Larger conductors and multiple conductors require larger radii.

Question 35Wiring Methods and Materials

What is the maximum permitted distance from a box to the first support for Type MC cable?

  1. 12 inches Correct answer.
  2. 36 inches
  3. 6 inches
  4. 24 inches

Explanation

Type MC cable must be secured within 12 inches of every box and at intervals not exceeding 6 feet. Securing near the box prevents strain on terminations. The 12-inch dimension is measured along the cable.

Question 36Wiring Methods and Materials

A metal raceway is installed in a concrete slab. Which requirement applies to the raceway where it emerges from the slab?

  1. It must be capped with a weatherproof box.
  2. It must be supported every 3 feet.
  3. It must be bonded to the rebar.
  4. It must be sealed to prevent moisture entry. Correct answer.

Explanation

Raceways emerging from concrete slabs must be arranged to prevent moisture from entering the raceway system. Sealing or draining provisions keep water out of boxes and equipment. Bonding to rebar and 3-foot support spacing are not the controlling requirements here.

Question 37Wiring Methods and Materials

Which of the following wiring methods is permitted for a 20-ampere branch circuit in a dwelling unit garage?

  1. Type CL3 cable
  2. Type SE cable used as interior branch wiring
  3. Type FCC cable under carpet
  4. Type NM cable Correct answer.

Explanation

Type NM cable is a standard permitted wiring method for branch circuits in dwelling unit garages. Flat conductor cable is limited to specific floor applications, and Class 3 cable is for signaling, not power. Service-entrance cable has restrictions on interior branch use.

Question 38Wiring Methods and Materials

A 1-inch electrical metallic tubing run contains six current-carrying conductors. What adjustment applies to the ampacity of the conductors?

  1. The ampacity must be reduced to 50 percent.
  2. The ampacity must be reduced to 80 percent. Correct answer.
  3. The ampacity must be reduced to 70 percent.
  4. No adjustment is required.

Explanation

When four to six current-carrying conductors are installed in a raceway, the ampacity must be adjusted to 80 percent of the table value. This accounts for the reduced ability to dissipate heat. Larger conductor counts require greater reductions.

Question 39Wiring Methods and Materials

What is the purpose of a bonding jumper around a water meter in a metal water piping system used as a grounding electrode?

  1. To reduce the pipe voltage to zero
  2. To increase water flow
  3. To bypass the insulating section and maintain a continuous grounding path Correct answer.
  4. To provide a neutral connection

Explanation

A water meter or insulating joint can interrupt the continuity of the metal piping used as a grounding electrode. A bonding jumper maintains a continuous, low-impedance path around that section. It does not serve to carry neutral current or to change water flow.

Question 40Wiring Methods and Materials

A metal outlet box is installed in a wall and the wiring method is Type NM cable. What is required for grounding the box?

  1. The box must be connected to an equipment grounding conductor or listed metal raceway. Correct answer.
  2. The box must be isolated from ground.
  3. The box must be bonded to the neutral conductor.
  4. No grounding is required for metal boxes.

Explanation

Metal boxes must be connected to an equipment grounding conductor or to a listed metal raceway that provides a grounding path. This ensures fault current can return to the source and trip the overcurrent device. Bonding to the neutral is prohibited on the load side of the service.

Question 41Wiring Methods and Materials

Which of the following conditions requires an expansion fitting in a rigid metal conduit run?

  1. A run installed entirely indoors
  2. A run with no bends
  3. A run between two fixed boxes where temperature changes cause significant expansion Correct answer.
  4. A run shorter than 10 feet

Explanation

Expansion fittings accommodate the length changes that occur when conduit is exposed to temperature variation, particularly between fixed terminations. Without them, expansion can buckle the conduit or damage boxes. Short indoor runs with no temperature extremes generally do not need them.

Question 42Wiring Methods and Materials

What is the minimum cover requirement for rigid metal conduit installed under a driveway in a residential setting?

  1. 12 inches
  2. 6 inches
  3. 18 inches Correct answer.
  4. 24 inches

Explanation

Rigid metal conduit buried under a residential driveway requires at least 18 inches of cover. Deeper cover is required for some other locations and shallower cover is allowed only in specific cases. The driveway condition increases the required depth to protect against vehicle loads.

Question 43Wiring Methods and Materials

Which of the following is a permitted use of surface metal raceway?

  1. Exposed on a wall to extend a circuit Correct answer.
  2. Concealed within a wall cavity
  3. Buried directly in soil
  4. Embedded in concrete

Explanation

Surface metal raceway is designed to be mounted on the surface of walls or ceilings to carry conductors where concealment is impractical. It is not intended for concealment in walls or burial in concrete or soil. Exposed mounting allows inspection and access.

Question 44Wiring Methods and Materials

A flexible metal conduit is used to connect a motor to a rigid raceway. What is the maximum length permitted where the flexible conduit is used as the equipment grounding means and the circuit is protected at 20 amperes?

  1. 10 feet
  2. 3 feet
  3. 25 feet
  4. 6 feet Correct answer.

Explanation

Flexible metal conduit may serve as an equipment grounding conductor only where the length is 6 feet or less and the circuit overcurrent device rating is within the permitted limits. The short length keeps the impedance low enough for fault clearing. Longer lengths require a separate grounding conductor.

Question 45Wiring Methods and Materials

What is the required marking on a box that indicates its capacity for conductor fill?

  1. The conduit trade size
  2. The cubic-inch capacity Correct answer.
  3. The ampacity rating
  4. The voltage rating

Explanation

Boxes must be marked with their cubic-inch capacity so that the number of conductors permitted can be calculated. The capacity accounts for conductors, devices, clamps, and grounding conductors. Ampacity, voltage, and conduit size are not box capacity markings.

Question 46Wiring Methods and Materials

A run of electrical nonmetallic tubing (ENT) is installed in a building. Which condition must be met for ENT to be permitted in a concealed location above a suspended ceiling?

  1. The ENT must be supported every 3 feet and secured within 12 inches of each box
  2. The ENT must be encased in at least 2 inches of concrete or masonry
  3. The ENT must be installed in a location that is not subject to physical damage and the ceiling cavity must be accessible Correct answer.
  4. The ceiling cavity must be accessible only by removable panels and the ENT must be listed for plenum use

Explanation

ENT is permitted in concealed locations where the space is accessible and the tubing is not subject to physical damage; the NEC treats ENT as a wiring method with specific concealment and protection limits. Support spacing is a separate installation requirement and does not authorize concealment by itself.

Question 47Wiring Methods and Materials

A rigid metal conduit (RMC) run is installed in a straight horizontal section between two boxes with threaded couplings. The conduit is steel and the ambient temperature swing is significant. What is the primary reason an expansion fitting is installed in this run?

  1. To allow the conduit to be removed without cutting during maintenance
  2. To compensate for the linear expansion and contraction of the conduit caused by temperature change Correct answer.
  3. To provide a bonding path across a threaded coupling
  4. To reduce the required support spacing on long horizontal runs

Explanation

RMC expands and contracts with temperature changes, and a long straight run can develop enough movement to damage supports, couplings, or terminations. An expansion fitting accommodates that linear movement while maintaining the raceway system.

Question 48Wiring Methods and Materials

A 1-inch electrical metallic tubing (EMT) run contains four 6 AWG THHN copper conductors, two of which are current-carrying. The run passes through a 24-inch length of a warm attic where the ambient temperature is 130°F. Which correction must be applied to the conductor ampacity?

  1. Apply only the ambient temperature correction factor for 130°F, because only two conductors are current-carrying Correct answer.
  2. Apply neither correction, because THHN is rated for wet and dry locations
  3. Apply only the conduit fill adjustment, because more than three conductors are in the raceway
  4. Apply both the ambient temperature correction and the conduit fill adjustment

Explanation

Conduit fill adjustment applies when more than three current-carrying conductors are in a raceway, and here only two are current-carrying, so no fill adjustment is required. The elevated ambient temperature, however, requires the ampacity to be corrected using the appropriate temperature correction factor for the conductor's insulation rating.

Question 49Wiring Methods and Materials

A metal outlet box is installed in a wall and is connected to a run of electrical metallic tubing (EMT) using listed fittings. The box contains a receptacle. What is required to ensure the box is effectively bonded?

  1. The box must be connected to a grounding electrode conductor sized per the service grounding table
  2. The box must be isolated from the raceway and bonded only through the receptacle mounting screws
  3. The box must be connected to an equipment grounding conductor or be bonded through the raceway system using listed fittings Correct answer.
  4. A separate bonding jumper from the box to the receptacle grounding terminal is the only permitted method

Explanation

Metal boxes must be bonded to the equipment grounding path, and listed EMT fittings provide a recognized bonding path through the raceway. Alternatively, an equipment grounding conductor can be run to the box, but the bonding requirement is satisfied by either an approved conductor or a listed raceway connection.

Question 50Wiring Methods and Materials

A feeder is installed in a rigid nonmetallic conduit (PVC) buried underground beneath a commercial parking lot. The conduit contains 4/0 AWG THHN copper conductors and is Schedule 40 PVC. Which installation requirement most directly governs the minimum burial depth and physical protection of this raceway?

  1. The conduit must be listed for direct burial and installed at the burial depth required for the raceway type and location Correct answer.
  2. The conduit must be encased in 2 inches of concrete regardless of burial depth
  3. The conduit must be installed with expansion fittings at both ends of the underground run
  4. The conduit must be supported every 3 feet throughout the underground portion

Explanation

Underground raceways must be listed for the application and buried at the depth the NEC specifies for the raceway type and the location, such as under a parking lot. Schedule 40 PVC is a recognized direct-burial raceway when installed at the required cover depth, and concrete encasement is an alternative method rather than a universal requirement.