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AR Electrician practice questions

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Question 1Electrical Theory, Principles, and General Knowledge

A 120-volt source is connected across a 12-ohm resistor. What current flows through the resistor?

  1. 132 A
  2. 1,440 A
  3. 10 A Correct answer.
  4. 0.10 A

Explanation

Ohm's law states that current equals voltage divided by resistance. Dividing 120 volts by 12 ohms gives 10 amperes.

Question 2Electrical Theory, Principles, and General Knowledge

A 120-volt circuit carries 10 amperes of current. What is the power consumed?

  1. 12 W
  2. 0.083 W
  3. 1,200 W Correct answer.
  4. 130 W

Explanation

In a resistive circuit, power equals voltage multiplied by current. Multiplying 120 volts by 10 amperes yields 1,200 watts.

Question 3Electrical Theory, Principles, and General Knowledge

Three resistors of 6 ohms, 9 ohms, and 15 ohms are connected in series. What is the total resistance of the circuit?

  1. 10 ohms
  2. 30 ohms Correct answer.
  3. 0.033 ohm
  4. 3.3 ohms

Explanation

Resistances in series add directly. The sum of 6, 9, and 15 ohms is 30 ohms.

Question 4Electrical Theory, Principles, and General Knowledge

Two 60-ohm resistors are connected in parallel. What is the total resistance?

  1. 120 ohms
  2. 30 ohms Correct answer.
  3. 60 ohms
  4. 3,600 ohms

Explanation

For two equal resistors in parallel, total resistance is half the value of one resistor. Parallel resistance is always less than the smallest individual resistor.

Question 5Electrical Theory, Principles, and General Knowledge

What is the period of a 60-hertz alternating current wave?

  1. 16.7 milliseconds Correct answer.
  2. 8.33 milliseconds
  3. 60 milliseconds
  4. 0.167 second

Explanation

Period is the reciprocal of frequency. One divided by 60 hertz equals 0.0167 second, or 16.7 milliseconds.

Question 6Electrical Theory, Principles, and General Knowledge

Which unit is used to express capacitance?

  1. Ohm
  2. Coulomb
  3. Farad Correct answer.
  4. Henry

Explanation

Capacitance is measured in farads, which express stored charge per volt. The henry measures inductance and the ohm measures resistance.

Question 7Electrical Theory, Principles, and General Knowledge

A sine wave has a peak voltage of 169.7 volts. What is its root-mean-square (RMS) voltage?

  1. 85 V
  2. 240 V
  3. 120 V Correct answer.
  4. 339 V

Explanation

RMS voltage equals peak voltage divided by the square root of two, about 1.414. Dividing 169.7 by 1.414 gives approximately 120 volts.

Question 8Electrical Theory, Principles, and General Knowledge

Which statement is true of a simple series circuit?

  1. Voltage is equal across each load.
  2. Current is the same at every point. Correct answer.
  3. Total resistance is below the smallest load.
  4. Current splits in proportion to resistance.

Explanation

A series circuit provides only one path for current, so the same current flows through every component. Voltage divides across the loads in proportion to their resistance.

Question 9Electrical Theory, Principles, and General Knowledge

A conductor with a total resistance of 0.2 ohm carries 15 amperes. What is the voltage drop along the conductor?

  1. 3 V Correct answer.
  2. 30 V
  3. 13.3 V
  4. 0.75 V

Explanation

Voltage drop equals current times conductor resistance. Multiplying 15 amperes by 0.2 ohm gives 3 volts.

Question 10Electrical Theory, Principles, and General Knowledge

A single-phase load draws 20 amperes at 240 volts with a power factor of 0.75. What is the real power?

  1. 1,800 W
  2. 48 W
  3. 3,600 W Correct answer.
  4. 4,800 W

Explanation

Real power equals voltage times current times power factor. Multiplying 240 volts, 20 amperes, and 0.75 gives 3,600 watts.

Question 11Electrical Theory, Principles, and General Knowledge

An ideal single-phase transformer steps 480 volts down to 120 volts. If the primary current is 20 amperes, what is the secondary current?

  1. 20 A
  2. 5 A
  3. 320 A
  4. 80 A Correct answer.

Explanation

In an ideal transformer, voltage and current change in inverse proportion. A 4-to-1 voltage step-down produces a 4-to-1 current step-up, so 20 amperes becomes 80 amperes.

Question 12Electrical Theory, Principles, and General Knowledge

How does current behave with respect to voltage in a pure capacitive AC circuit?

  1. Current lags the voltage by 90 degrees.
  2. Current leads the voltage by 90 degrees. Correct answer.
  3. Current is exactly in phase with the voltage.
  4. Current leads the voltage by 45 degrees.

Explanation

In a capacitor, current reaches its peak one quarter cycle before voltage does. This corresponds to current leading voltage by 90 electrical degrees.

Question 13Electrical Theory, Principles, and General Knowledge

A balanced three-phase load draws 50 amperes per phase at 480 volts with a power factor of 0.9. What is the real power?

  1. 37.4 kW Correct answer.
  2. 21.6 kW
  3. 24.0 kW
  4. 41.6 kW

Explanation

Three-phase real power equals the square root of three times line voltage times line current times power factor. Applying 1.732 times 480 times 50 times 0.9 gives about 37.4 kilowatts.

Question 14Electrical Theory, Principles, and General Knowledge

How does the resistance of a copper conductor change as its operating temperature rises?

  1. It stays constant.
  2. It decreases slightly.
  3. It increases. Correct answer.
  4. It falls to zero above 75 degrees Celsius.

Explanation

Copper has a positive temperature coefficient of resistance. As temperature rises, atomic vibration increases and resistance increases with it.

Question 15Electrical Theory, Principles, and General Knowledge

Which statement describes Kirchhoff's current law?

  1. Total resistance equals the sum of the individual resistances.
  2. Voltage drops around a closed loop sum to zero.
  3. Current entering a junction equals current leaving it. Correct answer.
  4. Power is the same in every resistor of a series circuit.

Explanation

Kirchhoff's current law is a statement of conservation of charge at a node. The total current entering a junction must equal the total current leaving it.

Question 16Electrical Theory, Principles, and General Knowledge

A 1,500-watt appliance runs for 4 hours. How much energy does it use?

  1. 600 kWh
  2. 6 kWh Correct answer.
  3. 0.375 kWh
  4. 375 kWh

Explanation

Energy in kilowatt-hours equals kilowatts multiplied by hours. Converting 1,500 watts to 1.5 kilowatts and multiplying by 4 hours gives 6 kilowatt-hours.

Question 17Electrical Theory, Principles, and General Knowledge

A 10-ohm resistor is connected in series with a parallel pair made of two 20-ohm resistors. What is the total resistance?

  1. 40 ohms
  2. 30 ohms
  3. 15 ohms
  4. 20 ohms Correct answer.

Explanation

The two 20-ohm resistors in parallel equal 10 ohms. Adding the series 10-ohm resistor to that 10-ohm equivalent gives 20 ohms.

Question 18Electrical Theory, Principles, and General Knowledge

What is the inductive reactance of a 0.1-henry inductor at 60 hertz?

  1. 6.0 ohms
  2. 0.6 ohm
  3. 37.7 ohms Correct answer.
  4. 377 ohms

Explanation

Inductive reactance equals 2 times pi times frequency times inductance. Applying 6.283 times 60 hertz times 0.1 henry gives about 37.7 ohms.

Question 19Electrical Theory, Principles, and General Knowledge

A wye-connected three-phase source has a phase voltage of 277 volts. What is its line-to-line voltage?

  1. 554 V
  2. 160 V
  3. 277 V
  4. 480 V Correct answer.

Explanation

In a wye connection, line voltage equals phase voltage multiplied by the square root of three. Multiplying 277 volts by 1.732 gives approximately 480 volts.

Question 20Electrical Theory, Principles, and General Knowledge

A coil with 6 ohms of resistance and 8 ohms of inductive reactance is connected to a 120-volt AC source. What current flows?

  1. 20 A
  2. 12 A Correct answer.
  3. 8.6 A
  4. 15 A

Explanation

Impedance is the vector sum of resistance and reactance, so it equals the square root of 6 squared plus 8 squared, or 10 ohms. Dividing 120 volts by 10 ohms gives 12 amperes.

Question 21Wiring Methods and Materials

Type NM cable installed in a dwelling is run horizontally through bored holes in wood joists. At what maximum interval must the cable be secured to the framing, and how close to each box must a support be placed?

  1. 4.5 ft; 8 in.
  2. 10 ft; 12 in.
  3. 6 ft; 12 in.
  4. 4.5 ft; 12 in. Correct answer.

Explanation

Type NM cable must be secured and supported at intervals not exceeding 1.4 m (4-1/2 ft) and within 300 mm (12 in.) of every box or fitting. The 12 in. dimension limits strain and abrasion where the cable enters the enclosure.

Question 22Wiring Methods and Materials

What is the maximum distance between supports for a straight horizontal run of 3/4 in. electrical metallic tubing (EMT)?

  1. 12 ft
  2. 6 ft
  3. 3 ft
  4. 10 ft Correct answer.

Explanation

EMT must be securely fastened in place at intervals not exceeding 3.0 m (10 ft). It must also be fastened within 900 mm (3 ft) of each box, cabinet, or termination.

Question 23Wiring Methods and Materials

A 120/240 V single-phase panelboard in a dwelling has 120 V to ground. No live parts are across the aisle. What is the minimum depth of the working space in front of the panelboard?

  1. 30 in.
  2. 24 in.
  3. 48 in.
  4. 36 in. Correct answer.

Explanation

Working space depth is based on the voltage to ground and the conditions across the aisle. For circuits of 0 to 150 V to ground with no live parts on the opposite side, the minimum depth is 900 mm (36 in.).

Question 24Wiring Methods and Materials

In a dwelling unit, what is the maximum distance that may be measured along the floor line of a wall from any point to the nearest receptacle outlet?

  1. 6 ft Correct answer.
  2. 12 ft
  3. 4 ft
  4. 8 ft

Explanation

Receptacle outlets must be installed so that no point along the floor line of any wall space is more than 1.8 m (6 ft) from an outlet in that space. This spacing rule prevents the use of long extension cords.

Question 25Wiring Methods and Materials

What volume must be counted for each 12 AWG conductor when calculating the required box fill?

  1. 2.50 cu in.
  2. 2.00 cu in.
  3. 2.25 cu in. Correct answer.
  4. 1.75 cu in.

Explanation

The box fill table assigns 2.25 cu in. per 12 AWG conductor, 2.00 cu in. per 14 AWG conductor, and 2.50 cu in. per 10 AWG conductor. These volumes are multiplied by the counted conductor equivalents.

Question 26Wiring Methods and Materials

How is a grounded circuit conductor identified in a wiring method?

  1. Green or green with yellow stripes
  2. Orange or blue
  3. White or gray Correct answer.
  4. Black or red

Explanation

Grounded conductors must be identified by a continuous white or gray outer finish, or by three continuous white stripes on other than green insulation. Green is reserved for equipment grounding conductors.

Question 27Wiring Methods and Materials

A splice is made in a run of Type NM cable overhead in a finished basement ceiling. May the splice box be covered with drywall so that it is hidden?

  1. Yes, if the circuit is protected by a GFCI breaker.
  2. No; boxes must remain accessible without removing building finish. Correct answer.
  3. Yes, if listed splicing connectors are used.
  4. Yes, if the box is listed as raintight.

Explanation

Boxes and conduit bodies must be accessible without removing any part of the building finish or structural member. A hidden splice prevents inspection, testing, and repair of the connections.

Question 28Wiring Methods and Materials

Type NM cable is pulled through a bored hole near the edge of a wood stud. What protection does the code require?

  1. Keep the hole at least 2 in. from the nearest edge or use a metal staple.
  2. Keep the hole at least 3 in. from the nearest edge or use a fiber insert.
  3. Keep the hole at least 1-1/4 in. from the nearest edge or use a steel plate. Correct answer.
  4. Keep the hole at least 1 in. from the nearest edge or use a plastic bushing.

Explanation

Cables run through bored holes in wood framing must be kept at least 32 mm (1-1/4 in.) from the nearest edge of the member, or the cable must be protected by a steel plate at least 1.6 mm (1/16 in.) thick. The protection prevents nails and screws driven into the framing from striking the cable.

Question 29Wiring Methods and Materials

Schedule 40 PVC conduit is direct buried to supply a detached garage on a 120/240 V residential circuit, with no vehicle traffic above it. What is the minimum cover depth?

  1. 24 in.
  2. 12 in.
  3. 30 in.
  4. 18 in. Correct answer.

Explanation

The burial depth table requires 450 mm (18 in.) of cover for rigid nonmetallic conduit rated 600 V or less where the run is not under a building, street, driveway, or parking area. Greater depths apply in those locations.

Question 30Wiring Methods and Materials

A raceway contains four current-carrying conductors. What maximum percentage of the raceway interior cross-sectional area may the conductors occupy?

  1. 60 percent
  2. 53 percent
  3. 31 percent
  4. 40 percent Correct answer.

Explanation

For three or more conductors in a raceway, the total conductor area may not exceed 40 percent of the raceway interior cross-sectional area. One conductor is limited to 53 percent and two conductors to 31 percent.

Question 31Wiring Methods and Materials

A junction box contains a straight pull of 3 in. rigid metal conduit entering through one wall and leaving through the opposite wall. What is the minimum length of the box?

  1. 16 in.
  2. 24 in. Correct answer.
  3. 36 in.
  4. 18 in.

Explanation

For a straight pull, the box length must be at least eight times the trade size of the largest raceway. Eight times 3 in. equals 24 in.

Question 32Wiring Methods and Materials

What is the maximum interval between supports for Type MC cable installed in a horizontal run?

  1. 4.5 ft
  2. 12 ft
  3. 6 ft Correct answer.
  4. 10 ft

Explanation

Type MC cable must be secured at intervals not exceeding 1.8 m (6 ft) and within 300 mm (12 in.) of every box or fitting. The shorter 4-1/2 ft interval applies to Type NM and flexible metal conduit.

Question 33Wiring Methods and Materials

Six current-carrying conductors are installed in a single raceway. What ampacity adjustment factor applies to the conductor ampacities?

  1. 85 percent
  2. 70 percent
  3. 80 percent Correct answer.
  4. 75 percent

Explanation

The adjustment table applies 80 percent to the ampacity of conductors where four to six current-carrying conductors share a raceway or cable. The factor drops as the conductor count rises.

Question 34Wiring Methods and Materials

A 60 A branch circuit is protected by a 60 A circuit breaker and is run with copper conductors in EMT. What is the minimum size copper equipment grounding conductor?

  1. 14 AWG
  2. 8 AWG
  3. 12 AWG
  4. 10 AWG Correct answer.

Explanation

The equipment grounding conductor size is selected from the table keyed to the rating of the overcurrent device protecting the circuit. A 60 A device requires a 10 AWG copper conductor.

Question 35Wiring Methods and Materials

A raceway nipple between two enclosures is 20 in. long. What maximum percentage of the nipple cross section may the conductors occupy?

  1. 60 percent Correct answer.
  2. 50 percent
  3. 40 percent
  4. 100 percent

Explanation

A nipple is a raceway section not exceeding 600 mm (24 in.) in length. Because of its short length, the fill may be increased to 60 percent of the interior cross-sectional area.

Question 36Wiring Methods and Materials

What is the maximum spacing between supports for flexible metal conduit in a straight run?

  1. 4.5 ft Correct answer.
  2. 6 ft
  3. 3 ft
  4. 10 ft

Explanation

Flexible metal conduit must be secured at intervals not exceeding 1.4 m (4-1/2 ft) and within 300 mm (12 in.) of each box or fitting. The closer spacing reflects the flexibility of the raceway.

Question 37Wiring Methods and Materials

At what point is a bushing or other fitting with a smoothly rounded insulating surface required where conductors enter a raceway or enclosure?

  1. A raceway containing only 14 AWG conductors
  2. Any raceway terminating in an enclosure
  3. A raceway containing 4 AWG or larger conductors Correct answer.
  4. A raceway installed in a wet location

Explanation

Where raceways contain 4 AWG or larger insulated circuit conductors and those conductors enter a cabinet, box, enclosure, or raceway, the conductors must be protected by a fitting with a smoothly rounded insulating surface. Smaller conductors are protected adequately by the standard locknut and bushing arrangement.

Question 38Wiring Methods and Materials

An outlet box is installed in a wall of noncombustible material. How far may the front edge of the box be set back from the finished wall surface?

  1. 1/4 in. Correct answer.
  2. 1/2 in.
  3. 1 in.
  4. 3/4 in.

Explanation

In walls or ceilings of concrete, tile, or other noncombustible material, boxes must be installed so the front edge is not set back more than 6 mm (1/4 in.) from the finished surface. Setting it back further can leave the device inaccessible or the cover plate short of the wall.

Question 39Wiring Methods and Materials

Type NM cable is run across the top of floor joists in an accessible attic with a scuttle opening. Within what distance of the edge of the scuttle must the cable be protected by guard strips?

  1. 4 ft
  2. 6 ft Correct answer.
  3. 8 ft
  4. 10 ft

Explanation

The NM cable article adopts the armored cable attic rules, which require guard strips or an equivalent physical protection where the cable is run near the attic access opening, within 1.8 m (6 ft) of its edge. The protection keeps persons entering the attic from stepping on or damaging the cable.

Question 40Wiring Methods and Materials

A box contains four 12 AWG ungrounded conductors, two 12 AWG grounded conductors, two 12 AWG equipment grounding conductors, and one duplex receptacle. What is the minimum box volume required?

  1. 18.00 cu in.
  2. 20.25 cu in. Correct answer.
  3. 24.75 cu in.
  4. 22.50 cu in.

Explanation

The four ungrounded and two grounded conductors count as six, the two equipment grounding conductors count as one, and the single yoke counts as two conductors of the largest size, giving nine conductor equivalents. Nine times 2.25 cu in. per 12 AWG conductor equals 20.25 cu in.

Question 41Wiring Methods and Materials

A service is supplied by 2/0 AWG copper service-entrance conductors. What is the minimum size copper grounding electrode conductor?

  1. 6 AWG copper
  2. 1/0 AWG copper
  3. 4 AWG copper Correct answer.
  4. 2 AWG copper

Explanation

The grounding electrode conductor table sizes the conductor according to the service-entrance conductor size. For 2/0 AWG copper service conductors, the minimum copper grounding electrode conductor is 4 AWG.

Question 42Wiring Methods and Materials

A 3 in. raceway makes a 90-degree angle pull into a junction box. What is the minimum distance from the raceway entry wall to the opposite wall of the box?

  1. 18 in. Correct answer.
  2. 30 in.
  3. 12 in.
  4. 24 in.

Explanation

For an angle or U pull, the distance from the raceway entry to the opposite wall must be at least six times the trade size of the largest raceway. Six times 3 in. equals 18 in.

Question 43Wiring Methods and Materials

Ten AWG copper conductors of a 30 A branch circuit are installed in Type NM cable. What is the maximum ampacity permitted for these conductors?

  1. 30 A Correct answer.
  2. 25 A
  3. 35 A
  4. 40 A

Explanation

The ampacity of conductors in Type NM cable is limited to the 60 degrees C column of the ampacity table regardless of the conductor insulation rating. Ten AWG copper at 60 degrees C carries 30 A.

Question 44Wiring Methods and Materials

A rigid metal conduit run crosses a structural expansion joint in a commercial building. What must be installed to accommodate movement of the building?

  1. An oversized pull box at the joint.
  2. A bonding jumper around the joint.
  3. An expansion fitting in the raceway. Correct answer.
  4. A rigid coupling on each side of the joint.

Explanation

Raceway systems must be able to compensate for thermal expansion and for building movement. Where a raceway crosses a building expansion joint, an expansion fitting is installed so the raceway can move without damage.

Question 45Services, Feeders, and Branch Circuits

What is the minimum permitted size for overhead service-drop conductors?

  1. 10 AWG copper or 8 AWG aluminum
  2. 8 AWG copper or 6 AWG aluminum Correct answer.
  3. 12 AWG copper or 10 AWG aluminum
  4. 6 AWG copper or 4 AWG aluminum

Explanation

Section 230.23 sets the minimum size of service-drop conductors at 8 AWG copper or 6 AWG aluminum or copper-clad aluminum, in addition to requiring enough ampacity for the calculated load. Smaller conductors are never permitted for a service drop, regardless of load.

Question 46Services, Feeders, and Branch Circuits

Where must the service disconnecting means for a building be installed?

  1. At the panelboard that carries the largest connected load
  2. At the property line, outdoors only
  3. Any point inside the building within 15 ft of the point of entry
  4. At a readily accessible location nearest the point of entry of the service conductors, either outside or inside the building Correct answer.

Explanation

Section 230.70(A)(1) requires the service disconnecting means to be installed at a readily accessible location, either outside the building or inside nearest the point of entry of the service conductors. The device must also be marked as suitable for use as service equipment.

Question 47Services, Feeders, and Branch Circuits

The service disconnecting means for a single service may consist of how many sets of switches or circuit breakers?

  1. Not more than four
  2. Not more than two
  3. Not more than six Correct answer.
  4. Not more than three

Explanation

Section 230.71 permits the service disconnecting means to consist of not more than six sets of switches or circuit breakers, grouped in one location, with each set marked to indicate the load it controls.

Question 48Services, Feeders, and Branch Circuits

A one-family dwelling kitchen must be served by at least how many 20-ampere small-appliance branch circuits?

  1. Three
  2. Two Correct answer.
  3. Four
  4. Six

Explanation

Section 210.11(C)(1) requires at least two 20-ampere small-appliance branch circuits for the receptacle outlets in the kitchen, pantry, breakfast room, and dining room of a dwelling unit.

Question 49Services, Feeders, and Branch Circuits

In a dwelling unit, receptacle outlets must be placed along the floor line of a wall space so that no point along the wall line is more than what distance from a receptacle outlet?

  1. 4 ft
  2. 8 ft
  3. 10 ft
  4. 6 ft Correct answer.

Explanation

Section 210.52(A)(1) requires receptacle outlets so that no point along the floor line in any wall space is more than 6 ft, measured horizontally, from an outlet in that space. This spacing rule keeps cords from being run long distances across floors.

Question 50Services, Feeders, and Branch Circuits

What is the minimum depth of working space in front of a 240-volt panelboard with exposed live parts on one side and no live or grounded parts on the other side (Condition 1)?

  1. 24 in
  2. 48 in
  3. 30 in
  4. 36 in Correct answer.

Explanation

Table 110.26(A)(1) requires a working space depth of at least 3 ft (36 in) for Condition 1, measured from the exposed live parts or the enclosure front. Deeper spaces are required as the conditions on the opposite side become more hazardous.