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WA Electrician practice questions

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Question 1General Electrical Knowledge, Theory, and Code Administration

A 120-volt circuit has a total resistance of 12 ohms. What current flows in the circuit?

  1. 12 amperes
  2. 1,440 amperes
  3. 10 amperes Correct answer.
  4. 0.1 ampere

Explanation

Ohm's law states that current equals voltage divided by resistance. Dividing 120 volts by 12 ohms gives 10 amperes. This relationship is the basis for nearly every branch-circuit calculation.

Question 2General Electrical Knowledge, Theory, and Code Administration

Two 12-ohm resistors are connected in parallel. What is the total resistance of the combination?

  1. 3 ohms
  2. 24 ohms
  3. 12 ohms
  4. 6 ohms Correct answer.

Explanation

For resistors of equal value in parallel, the equivalent resistance is the value of one resistor divided by the number of resistors. Twelve ohms divided by two equals 6 ohms. Adding the values would apply to a series connection instead.

Question 3General Electrical Knowledge, Theory, and Code Administration

A 120-volt appliance draws 10 amperes. How much power does it consume?

  1. 12,000 watts
  2. 120 watts
  3. 12 watts
  4. 1,200 watts Correct answer.

Explanation

Power in a resistive circuit equals voltage multiplied by current. Multiplying 120 volts by 10 amperes yields 1,200 watts. Dividing instead of multiplying would give a meaningless result for power.

Question 4General Electrical Knowledge, Theory, and Code Administration

Which insulation color identifies a grounded circuit conductor in a typical branch circuit?

  1. Green
  2. Red
  3. White or gray Correct answer.
  4. Black

Explanation

The grounded conductor of a circuit is required to be identified by a white or gray finish. Green is reserved for equipment grounding conductors, and black and red are commonly used for ungrounded conductors. Proper identification prevents accidental misconnection of the neutral.

Question 5General Electrical Knowledge, Theory, and Code Administration

What is the nominal voltage of a general-purpose lighting branch circuit in a typical dwelling unit?

  1. 240 volts
  2. 120 volts Correct answer.
  3. 480 volts
  4. 277 volts

Explanation

General lighting and receptacle branch circuits in dwellings operate at a nominal 120 volts. The 240-volt level serves large appliances, and 277 volts is a commercial lighting voltage derived from a 480Y/277-volt system.

Question 6General Electrical Knowledge, Theory, and Code Administration

In Washington, when must a permit be obtained for electrical work that requires one?

  1. Before the installation work begins Correct answer.
  2. Any time before the final inspection, including after rough-in
  3. Only if the serving utility asks for one at energization
  4. Within 30 days after the work is complete

Explanation

A permit must be secured before the regulated electrical work is started so the installation can be inspected at the rough-in stage. Obtaining a permit after the fact defeats the purpose of progressive inspection. The permitting requirement is administered by the authority having jurisdiction.

Question 7General Electrical Knowledge, Theory, and Code Administration

Ground-fault circuit-interrupter protection is required for 125-volt receptacles installed in which of these dwelling unit locations?

  1. A living room
  2. A bedroom
  3. An attic crawl space
  4. A bathroom Correct answer.

Explanation

Receptacles in dwelling unit bathrooms require GFCI protection because of the presence of water and grounded surfaces. Living rooms and bedrooms are covered by arc-fault protection requirements instead. GFCI protection may be provided by the receptacle itself or by the breaker.

Question 8General Electrical Knowledge, Theory, and Code Administration

What is the primary function of an equipment grounding conductor?

  1. Providing a low-impedance path for ground-fault current Correct answer.
  2. Balancing the load among the phases
  3. Reducing voltage drop on long circuits
  4. Carrying the normal return current of the circuit

Explanation

The equipment grounding conductor bonds non-current-carrying metal parts to the system grounding point so that fault current returns to the source and opens the overcurrent device. It carries current only during a fault. The grounded circuit conductor, by contrast, carries normal return current.

Question 9General Electrical Knowledge, Theory, and Code Administration

A single-phase 240-volt branch circuit carries 20 amperes over a two-wire run in which each conductor has a resistance of 0.4 ohm. What is the voltage drop at the load?

  1. 4 volts
  2. 16 volts Correct answer.
  3. 8 volts
  4. 32 volts

Explanation

Voltage drop in a two-wire circuit uses the total conductor length, so the current passes through the resistance twice. The calculation is 2 times 20 amperes times 0.4 ohm, which equals 16 volts. Using only one conductor's resistance understates the drop by half.

Question 10General Electrical Knowledge, Theory, and Code Administration

A conductor with 90°C insulation is terminated on a breaker whose terminals are rated 75°C. Which temperature rating governs the ampacity selected for the termination?

  1. 90°C
  2. 60°C
  3. 75°C Correct answer.
  4. The higher of 75°C and 90°C

Explanation

Ampacity at a termination is limited by the lowest temperature rating of any component in the circuit, which here is the 75°C breaker terminal. The 90°C insulation rating may still be used as the starting point for adjustment and correction calculations. The connection itself must not exceed its listed temperature.

Question 11General Electrical Knowledge, Theory, and Code Administration

A branch circuit supplies a continuous load of 16 amperes. What is the minimum branch-circuit rating permitted?

  1. 20 amperes Correct answer.
  2. 16 amperes
  3. 24 amperes
  4. 18 amperes

Explanation

Branch-circuit conductors and overcurrent devices serving continuous loads must be sized at not less than 125 percent of the continuous load. One hundred twenty-five percent of 16 amperes is 20 amperes. The 16-ampere figure ignores the continuous-load adder entirely.

Question 12General Electrical Knowledge, Theory, and Code Administration

What is the minimum width of the working space in front of electrical equipment?

  1. 30 inches or the width of the equipment, whichever is greater Correct answer.
  2. 36 inches
  3. 24 inches
  4. The width of the equipment door only

Explanation

The working space in front of electrical equipment must be at least 30 inches wide, or the width of the equipment, whichever is greater. The space must extend from the floor to the required height and be clear of obstructions. This ensures a person can safely stand and work.

Question 13General Electrical Knowledge, Theory, and Code Administration

Two 120-ohm resistors are connected in parallel, and that combination is connected in series with a 60-ohm resistor. What is the total resistance of the circuit?

  1. 180 ohms
  2. 60 ohms
  3. 120 ohms Correct answer.
  4. 240 ohms

Explanation

The parallel pair of equal resistors equals 60 ohms, and adding the series 60-ohm resistor gives 120 ohms. Resistance in series adds directly, while equal resistances in parallel divide. Solving the sections in the right order avoids double counting.

Question 14General Electrical Knowledge, Theory, and Code Administration

Four current-carrying 10 AWG conductors are installed in a single raceway. What ampacity adjustment factor applies for the bundled conductors?

  1. 100 percent
  2. 80 percent Correct answer.
  3. 50 percent
  4. 70 percent

Explanation

Adjustment factors for conductors bundled in a raceway step down as the number of current-carrying conductors increases, with four to six conductors adjusted to 80 percent. The factor is applied to the conductor ampacity before any other corrections. More conductors mean less ability to dissipate heat.

Question 15General Electrical Knowledge, Theory, and Code Administration

Which circuits in a dwelling unit require arc-fault circuit-interrupter protection?

  1. Only outdoor receptacle circuits
  2. All 120-volt, 15- and 20-ampere branch circuits supplying outlets in dwelling units Correct answer.
  3. Only circuits supplying bedroom receptacles
  4. Only circuits in unfinished basements

Explanation

Arc-fault protection is required for 120-volt, single-phase, 15- and 20-ampere branch circuits supplying outlets or devices in dwelling units. The requirement is not limited to bedrooms or basements. It addresses parallel and series arcing that can ignite building materials.

Question 16General Electrical Knowledge, Theory, and Code Administration

Where is the main bonding jumper installed?

  1. In every panelboard downstream of the service
  2. In the meter socket only, regardless of where the service disconnect is located
  3. At the service equipment, connecting the grounded conductor to the equipment grounding bus Correct answer.
  4. At the far end of the grounding electrode conductor

Explanation

The main bonding jumper is the connection between the grounded service conductor and the equipment grounding conductors, and it is made at the service equipment. It is the single point at which the grounding and grounded systems are joined. Installing it in downstream panels creates parallel return paths.

Question 17General Electrical Knowledge, Theory, and Code Administration

Using the standard method at 3 volt-amperes per square foot, what is the general lighting load for a 2,000-square-foot dwelling unit before demand factors are applied?

  1. 6,000 volt-amperes Correct answer.
  2. 9,000 volt-amperes
  3. 3,000 volt-amperes
  4. 4,500 volt-amperes

Explanation

The general lighting load is found by multiplying the floor area by the unit load for the occupancy. Two thousand square feet times 3 volt-amperes per square foot equals 6,000 volt-amperes. Demand factors are applied after the connected load is established.

Question 18General Electrical Knowledge, Theory, and Code Administration

A raceway containing more than two conductors may be filled to a maximum of what percentage of its interior cross-sectional area?

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

Explanation

The fill limit for a raceway containing more than two conductors is 40 percent of the interior cross-sectional area. One conductor may fill up to 53 percent and two conductors up to 31 percent. Lower fill allows conductors to be pulled without damage.

Question 19General Electrical Knowledge, Theory, and Code Administration

In a dwelling unit, what is the maximum distance, measured along the floor line, from any point on a wall to a receptacle outlet?

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

Explanation

Receptacles must be placed so that no point along the floor line of a wall space is more than 6 feet from an outlet. This effectively spaces receptacles no more than 12 feet apart. The rule limits the use of extension cords for lamps and appliances.

Question 20General Electrical Knowledge, Theory, and Code Administration

The service disconnecting means must be installed at a location that is:

  1. Within 25 feet of the utility meter
  2. At the point farthest from where the service conductors enter
  3. Inside a locked electrical vault
  4. Readily accessible and nearest to the point of entry of the service conductors Correct answer.

Explanation

Service disconnecting means must be readily accessible and located as near as practicable to the point where the service conductors enter the building. Keeping the disconnect close to the entry limits the length of unprotected service conductors inside the structure. Accessibility is required so the supply can be cut off quickly.

Question 21General Electrical Knowledge, Theory, and Code Administration

A balanced three-phase 480-volt feeder carries 60 amperes per phase, and each phase conductor has a resistance of 0.05 ohm. What is the approximate line-to-line voltage drop?

  1. About 3.0 volts
  2. About 9.0 volts
  3. About 1.7 volts
  4. About 5.2 volts Correct answer.

Explanation

For a balanced three-phase circuit, voltage drop is the square root of three times current times conductor resistance. Multiplying 1.732 by 60 amperes by 0.05 ohm gives about 5.2 volts. Omitting the square root factor understates the drop.

Question 22General Electrical Knowledge, Theory, and Code Administration

A 4-inch square metal box, 2-1/8 inches deep, has a capacity of 30.3 cubic inches. It contains six 12 AWG circuit conductors, one cable clamp, one device, and one equipment grounding conductor, with each 12 AWG counted at 2.25 cubic inches. What box volume is required?

  1. 31.5 cubic inches is required, so the box is inadequate
  2. 27.0 cubic inches is required, so the box is inadequate
  3. 13.5 cubic inches is required, so the box is adequate
  4. 22.5 cubic inches is required, so the box is adequate Correct answer.

Explanation

Six conductors count as 13.5 cubic inches, the clamp as one conductor at 2.25 cubic inches, the device yoke as two conductors at 4.5 cubic inches, and the grounding conductor as one at 2.25 cubic inches. The total is 22.5 cubic inches, which is less than the 30.3-cubic-inch capacity. Each fitting, device, and grounding conductor must be included in the count.

Question 23General Electrical Knowledge, Theory, and Code Administration

A single-phase transformer has a 480-volt primary and a 120-volt secondary. If the secondary supplies 20 amperes, what is the approximate primary current?

  1. 10 amperes
  2. 20 amperes
  3. 2.5 amperes
  4. 5 amperes Correct answer.

Explanation

The transformer passes essentially the same volt-amperes from primary to secondary. Twenty amperes at 120 volts is 2,400 volt-amperes, and dividing that by 480 volts gives 5 amperes in the primary. The current steps down in the same ratio that the voltage steps up.

Question 24General Electrical Knowledge, Theory, and Code Administration

A 10 AWG THHN copper conductor has a 90°C ampacity of 40 amperes. Six current-carrying conductors are installed in one raceway in a 40°C ambient, giving a bundle adjustment factor of 0.80 and an ambient correction factor of 0.91. What is the allowable ampacity?

  1. 32 amperes
  2. 36 amperes
  3. 29 amperes Correct answer.
  4. 40 amperes

Explanation

Both the bundle adjustment and the ambient correction are applied to the table ampacity. Forty amperes times 0.80 equals 32 amperes, and 32 amperes times 0.91 equals about 29 amperes. Applying only one of the factors overstates the conductor's capacity.

Question 25General Electrical Knowledge, Theory, and Code Administration

Under Washington law, who may perform electrical work for compensation?

  1. Any individual who has passed an inspector examination
  2. Any employee of the building owner
  3. A certified journeyman electrician working for a licensed electrical contractor, or a trainee supervised as allowed by rule Correct answer.
  4. Any person holding a valid general business license

Explanation

Electrical work for compensation must be performed by certified electricians working for a licensed electrical contractor, with trainees permitted only under the supervision allowed by rule. A general business license alone does not authorize electrical work. Holding a business license or being an employee does not substitute for certification.

Question 26General Electrical Knowledge, Theory, and Code Administration

A 120-volt source is connected across a 24-ohm resistive load. What current flows in the circuit?

  1. 0.2 ampere
  2. 5 amperes Correct answer.
  3. 2,880 amperes
  4. 40 amperes

Explanation

Ohm's law states that current equals voltage divided by resistance. Dividing 120 volts by 24 ohms gives 5 amperes, and the relationship holds for any purely resistive circuit.

Question 27General Electrical Knowledge, Theory, and Code Administration

A 240-volt branch circuit supplies a resistive load that draws 15 amperes at unity power factor. What is the power consumed by the load?

  1. 1,800 watts
  2. 225 watts
  3. 3,600 watts Correct answer.
  4. 16 watts

Explanation

For a resistive load at unity power factor, power in watts equals voltage multiplied by current. Multiplying 240 volts by 15 amperes gives 3,600 watts.

Question 28General Electrical Knowledge, Theory, and Code Administration

In a series circuit containing three resistors of different values, which quantity is the same for all three resistors?

  1. Power dissipated in each resistor
  2. Current through each resistor Correct answer.
  3. Voltage across each resistor
  4. Resistance of each resistor

Explanation

A series circuit provides only one path for current, so the same current passes through every component in the loop. Voltage divides among the resistors in proportion to their resistance, so the other quantities differ.

Question 29General Electrical Knowledge, Theory, and Code Administration

What is the period of an alternating-current waveform whose frequency is 60 hertz?

  1. 16.7 seconds
  2. 0.6 second
  3. 0.0167 second Correct answer.
  4. 60 seconds

Explanation

Period is the reciprocal of frequency, so one cycle lasts 1 divided by 60 seconds. That gives approximately 0.0167 second per cycle.

Question 30General Electrical Knowledge, Theory, and Code Administration

In a 120/240-volt single-phase, three-wire system, what is the function of the grounded neutral conductor?

  1. It carries the unbalanced current between the ungrounded conductors. Correct answer.
  2. It carries the total current of both ungrounded conductors at all times.
  3. It limits the voltage on the service equipment during a lightning surge.
  4. It provides the low-impedance fault path required for overcurrent devices to operate.

Explanation

The neutral of a three-wire system carries only the difference between the currents in the two ungrounded conductors, which becomes zero when the load is balanced. The equipment grounding conductor, not the neutral, is the intended fault-current path.

Question 31General Electrical Knowledge, Theory, and Code Administration

What does the term bonding mean in an electrical installation?

  1. Isolating metal parts so that they cannot become energized
  2. Joining metal parts to form a continuous conductive path Correct answer.
  3. Driving a rod into the earth to contact the soil
  4. Running a conductor from the panelboard to a water pipe only

Explanation

Bonding is the permanent joining of metal parts to form a path that ensures electrical continuity and can safely carry any current likely to be imposed. It is distinct from grounding, which is the intentional connection to earth.

Question 32General Electrical Knowledge, Theory, and Code Administration

What is the purpose of an overcurrent protective device?

  1. To balance the load among the ungrounded conductors
  2. To hold the circuit voltage steady during normal operation
  3. To provide the low-impedance path for fault current back to the source
  4. To open the circuit when current exceeds its rating Correct answer.

Explanation

Overcurrent devices such as fuses and circuit breakers sense current and open the circuit when it exceeds a set value, protecting conductors and equipment from overheating. The fault-current path that lets them operate is supplied by the equipment grounding and bonding system.

Question 33General Electrical Knowledge, Theory, and Code Administration

In Washington, what must a business obtain before advertising or offering to perform electrical work for compensation?

  1. A general contractor registration only
  2. An electrical contractor license issued by the state Correct answer.
  3. A trainee certificate for the owner
  4. A journeyman electrician certificate held by each employee

Explanation

Washington requires any person or entity that offers or performs electrical work for compensation to hold an electrical contractor license issued by the Department of Labor and Industries. Individual certificates qualify workers but do not authorize a business to contract for electrical work.

Question 34General Electrical Knowledge, Theory, and Code Administration

A copper conductor has a resistance of 0.40 ohm. It is replaced by a conductor of the same size and material that is twice as long. What is the new resistance?

  1. 1.60 ohm
  2. 0.40 ohm
  3. 0.20 ohm
  4. 0.80 ohm Correct answer.

Explanation

Resistance of a conductor is directly proportional to its length, so doubling the length of the same size and type of conductor doubles the resistance. Twice 0.40 ohm is 0.80 ohm.

Question 35General Electrical Knowledge, Theory, and Code Administration

At a junction, two conductors bring 4 amperes and 6 amperes into the junction and a third conductor carries all the current away. What current does the third conductor carry?

  1. 2 amperes
  2. 10 amperes Correct answer.
  3. 4 amperes
  4. 24 amperes

Explanation

Kirchhoff's current law requires that the total current entering a junction equal the total current leaving it. The entering currents add to 10 amperes, so 10 amperes must leave the junction.

Question 36General Electrical Knowledge, Theory, and Code Administration

A sinusoidal voltage has an effective (RMS) value of 120 volts. What is its approximate peak value?

  1. 120 volts
  2. 170 volts Correct answer.
  3. 240 volts
  4. 85 volts

Explanation

For a sine wave, the peak value equals the RMS value multiplied by about 1.414. Multiplying 120 volts by 1.414 gives approximately 170 volts.

Question 37General Electrical Knowledge, Theory, and Code Administration

A single-phase 240-volt circuit carries 20 amperes at a power factor of 0.80. What is the real power delivered?

  1. 960 watts
  2. 4,800 watts
  3. 3,840 watts Correct answer.
  4. 3,000 watts

Explanation

Apparent power is voltage times current, or 4,800 volt-amperes, and real power is apparent power multiplied by the power factor. Multiplying 4,800 by 0.80 gives 3,840 watts.

Question 38General Electrical Knowledge, Theory, and Code Administration

A conductor is installed where the ambient temperature is higher than the 30°C base used in the ampacity tables. How does this affect the conductor?

  1. Its ampacity must be reduced by applying a correction factor. Correct answer.
  2. Its ampacity increases because heat leaves the conductor faster.
  3. Its ampacity is unchanged, but the overcurrent device must be increased.
  4. Its ampacity is unchanged because only the number of conductors matters.

Explanation

Ampacity tables are based on a 30°C ambient, and a conductor in a hotter location cannot dissipate heat as effectively. The tables provide temperature correction factors that reduce allowable ampacity when the ambient exceeds the base value.

Question 39General Electrical Knowledge, Theory, and Code Administration

How often must straight runs of electrical metallic tubing be securely supported?

  1. At least every 10 feet Correct answer.
  2. At least every 20 feet
  3. At least every 5 feet
  4. At least every 3 feet

Explanation

Electrical metallic tubing must be supported within 3 feet of each box or fitting and at intervals not exceeding 10 feet along the run. Intermediate supports keep the raceway from sagging and separating at couplings.

Question 40General Electrical Knowledge, Theory, and Code Administration

The NEC recommends that the voltage drop over a feeder plus branch circuit not exceed what percentage of the supply voltage?

  1. 3 percent
  2. 10 percent
  3. 5 percent Correct answer.
  4. 2 percent

Explanation

Informational notes in the Code recommend a maximum total voltage drop of 5 percent from the service point to the outlet. Within that total, no more than 3 percent is recommended on a branch circuit and 2 percent on a feeder.

Question 41General Electrical Knowledge, Theory, and Code Administration

What is the purpose of a motor overload protective device?

  1. To protect the branch-circuit conductors from ground faults
  2. To open the circuit when the supply voltage is lost
  3. To clear a short circuit in the branch-circuit conductors quickly
  4. To protect the motor from overheating under sustained overload Correct answer.

Explanation

Overload protection responds to a sustained current above the motor's rating and is intended to prevent the winding from overheating. Short circuits and ground faults are cleared by the branch-circuit short-circuit and ground-fault protective device.

Question 42General Electrical Knowledge, Theory, and Code Administration

What is the allowable ampacity of 12 AWG copper conductors with 60°C-rated insulation where no more than three current-carrying conductors are in the raceway and the ambient is 30°C?

  1. 30 amperes
  2. 20 amperes Correct answer.
  3. 15 amperes
  4. 25 amperes

Explanation

In the 60°C column of the ampacity table, 12 AWG copper has an allowable ampacity of 20 amperes. No adjustment or correction applies with three or fewer current-carrying conductors at an ambient of 30°C.

Question 43General Electrical Knowledge, Theory, and Code Administration

Which NEC article contains the general requirements for grounding and bonding?

  1. Article 430
  2. Article 210
  3. Article 300
  4. Article 250 Correct answer.

Explanation

Article 250 of the National Electrical Code covers grounding and bonding of electrical systems and equipment. The other articles named address branch circuits, general wiring methods, and motors respectively.

Question 44General Electrical Knowledge, Theory, and Code Administration

Under Article 90, how is the National Electrical Code described?

  1. A design manual that specifies the exact equipment and wiring methods to be installed
  2. A maintenance manual that applies only to existing installations
  3. A guide that may be disregarded where local practice differs
  4. A practical safeguarding document that is not intended as a design specification Correct answer.

Explanation

Article 90 states that the Code is intended for the practical safeguarding of persons and property from hazards arising from the use of electricity and is not intended as a design specification. It sets minimum safety provisions rather than a complete design guide.

Question 45General Electrical Knowledge, Theory, and Code Administration

How is the grounded conductor of a premises wiring system required to be identified?

  1. Orange
  2. Green
  3. Black or red
  4. White or gray Correct answer.

Explanation

The grounded conductor must be identified by a continuous white or gray finish, or by three continuous white stripes where the insulation is a color other than green. Green is reserved for the equipment grounding conductor.

Question 46General Electrical Knowledge, Theory, and Code Administration

A balanced three-phase, 480-volt feeder supplies 50 amperes per phase at unity power factor. What is the approximate power delivered?

  1. 72.0 kilowatts
  2. 24.0 kilowatts
  3. 13.9 kilowatts
  4. 41.6 kilowatts Correct answer.

Explanation

Three-phase power equals the square root of three times line voltage times line current times power factor. Multiplying 1.732 by 480 volts by 50 amperes gives about 41,600 watts, or 41.6 kilowatts.

Question 47General Electrical Knowledge, Theory, and Code Administration

A circuit contains resistance and inductance. How does the alternating current behave with respect to the voltage?

  1. The current is exactly in phase with the voltage
  2. The current is 180 degrees out of phase with the voltage
  3. The current lags the voltage Correct answer.
  4. The current leads the voltage

Explanation

Inductance opposes changes in current, so in an inductive circuit the current reaches its peak after the voltage does, lagging by an angle between 0 and 90 degrees. Capacitance produces the opposite effect, with current leading voltage.

Question 48General Electrical Knowledge, Theory, and Code Administration

Why is the alternating-current resistance of a large conductor greater than its direct-current resistance?

  1. Skin effect reduces the effective cross-section of the conductor Correct answer.
  2. The conductor operates at a higher temperature on alternating current in every case
  3. Alternating current travels only through the air surrounding the conductor
  4. The insulation absorbs a portion of the alternating current

Explanation

In alternating current, the changing magnetic field within the conductor causes current to concentrate toward the outer surface, a phenomenon called skin effect. This reduces the effective conducting area and raises resistance above the direct-current value, most noticeably in large conductors.

Question 49General Electrical Knowledge, Theory, and Code Administration

A 24-volt source is connected to a 6-ohm resistor in series with an 18-ohm resistor. What is the voltage across the 18-ohm resistor?

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

Explanation

The total series resistance is 24 ohms, so the current is 24 volts divided by 24 ohms, or 1 ampere. The voltage across the 18-ohm resistor is 1 ampere times 18 ohms, or 18 volts.

Question 50General Electrical Knowledge, Theory, and Code Administration

A circuit breaker is to be installed at a point where the available fault current is 22,000 amperes. What requirement applies to the breaker?

  1. No rating check is needed as long as the breaker is listed.
  2. Its continuous current rating must be at least 22,000 amperes.
  3. Its interrupting rating must be at least 22,000 amperes. Correct answer.
  4. Its adjustable trip setting must be set at 22,000 amperes.

Explanation

A circuit breaker must have an interrupting rating not less than the available fault current at its line terminals so that it can safely clear a fault without damage. The continuous current rating is selected for the load and has no relationship to the fault current.