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Question 1Laws of Electricity and Electrical Codes

In an electrical circuit, what does Ohm's law state about the relationship among voltage, current, and resistance?

  1. Current equals voltage divided by resistance
  2. Resistance equals current divided by voltage
  3. Voltage equals current multiplied by resistance Correct answer.
  4. Power equals voltage multiplied by current

Explanation

Ohm's law is expressed as V = I × R, meaning voltage across a component equals the current through it times its resistance. The other relationships derive from this formula and must be rearranged correctly to be valid.

Question 2Laws of Electricity and Electrical Codes

A resistor of 240 ohms is connected across a 120-volt source. What current flows through the resistor?

  1. 0.25 A
  2. 28,800 A
  3. 2 A
  4. 0.5 A Correct answer.

Explanation

Using Ohm's law, current equals voltage divided by resistance: I = 120 V ÷ 240 Ω = 0.5 A. Multiplying instead of dividing or mishandling units produces the distractors.

Question 3Laws of Electricity and Electrical Codes

Which unit is used to express electrical resistance in the SI system?

  1. Ohm Correct answer.
  2. Watt
  3. Volt
  4. Ampere

Explanation

Resistance is measured in ohms, symbolized by the Greek letter omega. The ampere measures current, the volt measures potential difference, and the watt measures power.

Question 4Laws of Electricity and Electrical Codes

A 1,500-watt load operates on a 120-volt branch circuit. What is the current drawn by this load?

  1. 0.08 A
  2. 180,000 A
  3. 8 A
  4. 12.5 A Correct answer.

Explanation

Power equals voltage times current, so current equals power divided by voltage: I = 1,500 W ÷ 120 V = 12.5 A. This is the standard method for sizing conductors and overcurrent devices.

Question 5Laws of Electricity and Electrical Codes

According to Kirchhoff's current law, what is true at any node in a circuit?

  1. The total current entering a node equals the total current leaving it Correct answer.
  2. The total resistance equals the sum of all resistances
  3. The sum of voltages around the loop equals zero
  4. The total power equals the product of all branch currents

Explanation

Kirchhoff's current law states that charge is conserved at a node, so the sum of currents entering equals the sum of currents leaving. The voltage-loop statement describes Kirchhoff's voltage law instead.

Question 6Laws of Electricity and Electrical Codes

Two resistors, 60 ohms and 120 ohms, are connected in series. What is the total resistance of the combination?

  1. 80 ohms
  2. 40 ohms
  3. 7,200 ohms
  4. 180 ohms Correct answer.

Explanation

In a series circuit, resistances add directly: 60 Ω + 120 Ω = 180 Ω. The current is the same through both resistors, and the total resistance is simply the sum.

Question 7Laws of Electricity and Electrical Codes

What is the primary purpose of the equipment grounding conductor in a branch circuit?

  1. To balance the load across phases
  2. To provide a low-impedance path for fault current Correct answer.
  3. To reduce the voltage drop along the circuit
  4. To carry normal operating current back to the source

Explanation

The equipment grounding conductor provides a low-impedance return path for fault current so that overcurrent devices operate quickly. It does not normally carry operating current, which travels on the grounded and ungrounded conductors.

Question 8Laws of Electricity and Electrical Codes

Which color is generally reserved for the grounded conductor (neutral) in a typical branch circuit?

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

Explanation

The NEC identifies white or gray as the standard color for the grounded conductor. Green is reserved for equipment grounding, while black and red are typically ungrounded (hot) conductors.

Question 9Laws of Electricity and Electrical Codes

A 20-ampere branch circuit supplies a continuous load. According to the standard overcurrent sizing rule, what is the minimum overcurrent device rating for the continuous portion plus the noncontinuous load?

  1. The continuous load at 125% plus the noncontinuous load at 100% Correct answer.
  2. The continuous load at 150% plus the noncontinuous load at 100%
  3. The continuous load at 100% plus the noncontinuous load at 125%
  4. The continuous load at 100% plus the noncontinuous load at 100%

Explanation

Overcurrent devices and conductors serving continuous loads must be sized at not less than 125% of the continuous load plus 100% of the noncontinuous load. This accounts for the heat buildup from loads operating for three hours or more.

Question 10Laws of Electricity and Electrical Codes

A conductor has a resistance of 0.5 ohm per 1,000 feet. What is the approximate resistance of a 250-foot run of this conductor?

  1. 2 ohms
  2. 0.25 ohm
  3. 0.5 ohm
  4. 0.125 ohm Correct answer.

Explanation

Resistance is directly proportional to length. At 0.5 ohm per 1,000 feet, a 250-foot run has one quarter of that resistance: 0.5 × (250/1,000) = 0.125 ohm.

Question 11Laws of Electricity and Electrical Codes

What effect does increasing the length of a conductor have on its resistance, assuming the material and cross-sectional area remain constant?

  1. Resistance increases in proportion to length Correct answer.
  2. Resistance decreases in proportion to length
  3. Resistance increases with the square of the length
  4. Resistance remains unchanged

Explanation

Conductor resistance is directly proportional to length according to the formula R = ρL/A. Doubling the length doubles the resistance, which is why long runs experience greater voltage drop.

Question 12Laws of Electricity and Electrical Codes

An alternating current completes 60 full cycles each second. What is its frequency?

  1. 60 hertz Correct answer.
  2. 30 hertz
  3. 0.0167 hertz
  4. 120 hertz

Explanation

Frequency is the number of complete cycles per second, expressed in hertz. Sixty cycles per second equals 60 Hz, the standard power-line frequency in the United States.

Question 13Laws of Electricity and Electrical Codes

In a purely resistive AC circuit, how do voltage and current relate in phase?

  1. Current lags voltage by 90 degrees
  2. Voltage and current are 180 degrees out of phase
  3. Voltage and current are in phase Correct answer.
  4. Current leads voltage by 90 degrees

Explanation

In a resistive circuit, voltage and current reach their peaks at the same instant, so they are in phase. Phase shifts of 90 degrees occur with pure inductance or capacitance.

Question 14Laws of Electricity and Electrical Codes

Three resistors of 30 ohms each are connected in parallel. What is the equivalent resistance?

  1. 30 ohms
  2. 15 ohms
  3. 90 ohms
  4. 10 ohms Correct answer.

Explanation

For equal resistors in parallel, the equivalent resistance is the value of one resistor divided by the number of resistors: 30 Ω ÷ 3 = 10 Ω. The reciprocal formula confirms this result.

Question 15Laws of Electricity and Electrical Codes

A branch circuit supplies a 1,200-watt load at 120 volts over a run where the conductors have a total resistance of 0.4 ohm. What is the approximate voltage drop in the conductors?

  1. 40 volts
  2. 48 volts
  3. 10 volts
  4. 4 volts Correct answer.

Explanation

First find the current: 1,200 W ÷ 120 V = 10 A. Then voltage drop equals current times conductor resistance: 10 A × 0.4 Ω = 4 V. This two-step application combines the power and Ohm's law formulas.

Question 16Laws of Electricity and Electrical Codes

Which of the following best describes the function of a fuse in an electrical circuit?

  1. It limits the voltage supplied to the load
  2. It opens the circuit when current exceeds its rating Correct answer.
  3. It converts alternating current to direct current
  4. It stores energy for later use by the load

Explanation

A fuse contains a link that melts and opens the circuit when current exceeds its rating, protecting conductors from overheating. It is a one-time overcurrent protective device, unlike a resettable circuit breaker.

Question 17Laws of Electricity and Electrical Codes

A 120-volt circuit has a total load of 1,800 volt-amperes. What minimum standard-size overcurrent device is appropriate if the circuit is not a continuous load?

  1. 10 A
  2. 30 A
  3. 20 A
  4. 15 A Correct answer.

Explanation

The load current is 1,800 VA ÷ 120 V = 15 A. For a noncontinuous load, the overcurrent device must be at least the load current, and 15 A is the smallest standard size that meets this requirement.

Question 18Laws of Electricity and Electrical Codes

What is the purpose of bonding in an electrical installation?

  1. To insulate exposed metal from fault current
  2. To reduce the frequency of the supply
  3. To connect metal parts together to ensure electrical continuity Correct answer.
  4. To increase the current-carrying capacity of conductors

Explanation

Bonding connects metallic parts to form a continuous conductive path, ensuring they remain at the same potential and allowing fault current to return to the source. This keeps touch voltages low and helps overcurrent devices operate.

Question 19Laws of Electricity and Electrical Codes

A 240-volt single-phase circuit supplies a resistive heater drawing 15 amperes. What is the power consumed by the heater?

  1. 4,800 W
  2. 1,600 W
  3. 16 W
  4. 3,600 W Correct answer.

Explanation

Power equals voltage times current for a resistive load: 240 V × 15 A = 3,600 W. This is the standard single-phase power calculation used for load sizing.

Question 20Laws of Electricity and Electrical Codes

Which of the following materials is generally classified as a conductor of electricity?

  1. Dry wood
  2. Rubber
  3. Copper Correct answer.
  4. Glass

Explanation

Copper has many free electrons and low resistance, making it a widely used conductor. Rubber, glass, and dry wood are insulators that resist the flow of current.

Question 21Laws of Electricity and Electrical Codes

Two resistors, 100 ohms and 100 ohms, are connected in series across a 200-volt source. What is the voltage across each resistor?

  1. 50 V each
  2. 100 V each Correct answer.
  3. 200 V each
  4. 0 V each

Explanation

The total resistance is 200 Ω, so the current is 200 V ÷ 200 Ω = 1 A. Each 100-ohm resistor then drops 1 A × 100 Ω = 100 V, and the two drops sum to the source voltage.

Question 22Laws of Electricity and Electrical Codes

A 3-phase, 480-volt circuit supplies a balanced load drawing 20 amperes per phase at unity power factor. What is the approximate power delivered?

  1. 9,600 W
  2. 5,547 W
  3. 16,627 W Correct answer.
  4. 28,800 W

Explanation

For a balanced three-phase circuit, power equals √3 × voltage × current × power factor: 1.732 × 480 × 20 × 1 ≈ 16,627 W. Multiplying voltage by current alone would ignore the three-phase relationship.

Question 23Laws of Electricity and Electrical Codes

In a circuit with both resistance and inductance, what does the term power factor represent?

  1. The ratio of voltage to current
  2. The ratio of true power to apparent power Correct answer.
  3. The ratio of resistance to capacitive reactance
  4. The product of voltage and current

Explanation

Power factor is the cosine of the phase angle between voltage and current, equal to true power divided by apparent power. A purely resistive load has a power factor of 1, while inductive loads reduce it.

Question 24Laws of Electricity and Electrical Codes

A conductor carrying 30 amperes has a resistance of 0.02 ohm. How much power is dissipated as heat in this conductor?

  1. 18 W Correct answer.
  2. 0.6 W
  3. 60 W
  4. 9 W

Explanation

Conductor heating follows P = I²R: 30² × 0.02 = 900 × 0.02 = 18 W. This relationship explains why undersized conductors overheat under heavy current.

Question 25Laws of Electricity and Electrical Codes

A 120-volt circuit experiences a 6-volt drop across its conductors while supplying a 12-ampere load. What is the total resistance of the conductors in this run?

  1. 0.05 ohm
  2. 20 ohms
  3. 0.5 ohm Correct answer.
  4. 2 ohms

Explanation

Voltage drop equals current times conductor resistance, so R = V ÷ I = 6 V ÷ 12 A = 0.5 ohm. This is the total resistance of both the outgoing and return conductors in the run.

Question 26Laws of Electricity and Electrical Codes

A dwelling unit's branch circuit supplies a 1,500-watt load at 120 volts. What current does the load draw?

  1. 10.0 amperes
  2. 18.0 amperes
  3. 15.0 amperes
  4. 12.5 amperes Correct answer.

Explanation

Ohm's law power form gives I = P / V. Dividing 1,500 watts by 120 volts yields 12.5 amperes, which is the current the branch circuit must carry.

Question 27Laws of Electricity and Electrical Codes

Which quantity is measured in volts in an electrical circuit?

  1. Electrical potential difference Correct answer.
  2. Power delivered
  3. Current flow rate
  4. Resistance to current

Explanation

The volt is the unit of electrical potential difference, the force that drives current between two points. Current is measured in amperes, resistance in ohms, and power in watts.

Question 28Laws of Electricity and Electrical Codes

In a standard branch circuit, which conductor is intended to carry current during normal operation and is commonly color-coded black or red?

  1. The equipment grounding conductor
  2. The bonding jumper
  3. The grounded (neutral) conductor
  4. The ungrounded (hot) conductor Correct answer.

Explanation

The ungrounded conductor, often called the hot conductor, carries current to the load under normal conditions and is typically black or red. The grounded conductor and grounding conductor serve different roles.

Question 29Laws of Electricity and Electrical Codes

What does the abbreviation AWG refer to when selecting branch-circuit conductors?

  1. American Wire Gauge, a standard sizing system for conductors Correct answer.
  2. Automatic Wiring Guard, a protective enclosure rating
  3. Ampere Watt Gradient, a rating for overcurrent devices
  4. Alternating Wave Generator, a type of power source

Explanation

AWG stands for American Wire Gauge, the standardized system used to designate conductor sizes in North American electrical work. Larger AWG numbers correspond to smaller conductor diameters.

Question 30Laws of Electricity and Electrical Codes

Which of the following is the standard unit of electrical resistance?

  1. The ampere
  2. The coulomb
  3. The henry
  4. The ohm Correct answer.

Explanation

Resistance is measured in ohms, symbolized by the Greek letter omega. The ampere measures current, the coulomb measures charge, and the henry measures inductance.

Question 31Laws of Electricity and Electrical Codes

A circuit contains a 12-volt source and a 4-ohm resistor. What current flows through the resistor?

  1. 48 amperes
  2. 8 amperes
  3. 3 amperes Correct answer.
  4. 0.33 ampere

Explanation

Ohm's law states that current equals voltage divided by resistance. Dividing 12 volts by 4 ohms gives 3 amperes.

Question 32Laws of Electricity and Electrical Codes

What is the function of a circuit breaker in a branch circuit?

  1. To convert alternating current to direct current
  2. To open the circuit automatically when current exceeds its rating Correct answer.
  3. To step down voltage before the load
  4. To improve the power factor of inductive loads

Explanation

A circuit breaker is an overcurrent protective device that trips open when current exceeds its rating, protecting conductors from overheating. It does not change voltage, rectify current, or correct power factor.

Question 33Laws of Electricity and Electrical Codes

In a series circuit, how does the current behave through each component?

  1. Current is zero in all but the first component
  2. The same current flows through every component Correct answer.
  3. Current divides among the components
  4. Current doubles at each successive component

Explanation

A series circuit provides only one path for current, so the same current must flow through every component in the loop. Voltage, not current, divides across series components.

Question 34Laws of Electricity and Electrical Codes

A 240-volt circuit supplies a load drawing 10 amperes at unity power factor. What is the apparent power in volt-amperes?

  1. 240 volt-amperes
  2. 2,400 volt-amperes Correct answer.
  3. 24 volt-amperes
  4. 2.4 volt-amperes

Explanation

Apparent power equals voltage multiplied by current. Multiplying 240 volts by 10 amperes yields 2,400 volt-amperes, and at unity power factor this equals the real power.

Question 35Laws of Electricity and Electrical Codes

A conductor with a cross-sectional area of 10,000 circular mils has a resistance of 1 ohm per 1,000 feet. What is the approximate resistance of 500 feet of the same conductor?

  1. 1.0 ohm
  2. 0.5 ohm Correct answer.
  3. 2.0 ohms
  4. 0.25 ohm

Explanation

Resistance is directly proportional to conductor length. Halving the length from 1,000 feet to 500 feet halves the resistance from 1 ohm to 0.5 ohm.

Question 36Laws of Electricity and Electrical Codes

What is the primary purpose of a grounding electrode system at a building?

  1. To establish a reference connection to earth for the electrical system Correct answer.
  2. To increase the current-carrying capacity of branch circuits
  3. To reduce the voltage drop along feeders
  4. To provide a return path for normal load current

Explanation

The grounding electrode system connects the electrical system to the earth, establishing a reference potential and helping dissipate fault and lightning currents. It does not carry normal load current or increase ampacity.

Question 37Laws of Electricity and Electrical Codes

A 120-volt branch circuit supplies a 600-watt load. What is the current drawn by the load?

  1. 5 amperes Correct answer.
  2. 0.2 ampere
  3. 2 amperes
  4. 72 amperes

Explanation

Current equals power divided by voltage. Dividing 600 watts by 120 volts gives 5 amperes, which is within the capacity of a standard 15- or 20-ampere branch circuit.

Question 38Laws of Electricity and Electrical Codes

Two 6-ohm resistors are connected in parallel. What is the equivalent resistance of the combination?

  1. 12 ohms
  2. 6 ohms
  3. 1.5 ohms
  4. 3 ohms Correct answer.

Explanation

For two equal resistors in parallel, the equivalent resistance is half the value of one resistor. Half of 6 ohms is 3 ohms, consistent with the reciprocal formula.

Question 39Laws of Electricity and Electrical Codes

Which of the following best describes the relationship between electrical energy and power?

  1. Energy is power multiplied by time Correct answer.
  2. Energy is power divided by time
  3. Energy is power divided by voltage
  4. Energy is power multiplied by resistance

Explanation

Power is the rate of energy transfer, so energy equals power multiplied by the duration of transfer. A kilowatt-hour, for example, is 1,000 watts delivered for one hour.

Question 40Laws of Electricity and Electrical Codes

A 3-phase, 208-volt circuit supplies a balanced resistive load drawing 30 amperes per phase. What is the approximate apparent power?

  1. 18,720 volt-amperes
  2. 3,600 volt-amperes
  3. 10,800 volt-amperes Correct answer.
  4. 6,240 volt-amperes

Explanation

For a balanced 3-phase circuit, apparent power equals the square root of three multiplied by line voltage and line current. Approximately 1.732 times 208 volts times 30 amperes yields about 10,800 volt-amperes.

Question 41Laws of Electricity and Electrical Codes

A conductor carries 20 amperes and has a resistance of 0.05 ohm. What power is dissipated as heat in the conductor?

  1. 400 watts
  2. 20 watts Correct answer.
  3. 1 watt
  4. 0.1 watt

Explanation

Power dissipated in a resistor equals current squared times resistance. Squaring 20 amperes gives 400, and multiplying by 0.05 ohm yields 20 watts of heat loss.

Question 42Laws of Electricity and Electrical Codes

What does the term ampacity describe for a conductor?

  1. The maximum voltage it can withstand before breakdown
  2. The insulation temperature rating alone
  3. The maximum current it can carry continuously under stated conditions Correct answer.
  4. The total resistance per unit length

Explanation

Ampacity is the maximum current a conductor can carry continuously without exceeding its temperature rating under the conditions of use. It depends on conductor material, size, insulation, and installation conditions.

Question 43Laws of Electricity and Electrical Codes

A 120-volt circuit supplies a load with 1,200 volt-amperes at a power factor of 0.8. What is the real power consumed?

  1. 1,500 watts
  2. 1,200 watts
  3. 768 watts
  4. 960 watts Correct answer.

Explanation

Real power equals apparent power multiplied by the power factor. Multiplying 1,200 volt-amperes by 0.8 gives 960 watts, with the remainder representing reactive power.

Question 44Laws of Electricity and Electrical Codes

Why is a higher voltage generally preferred for long-distance power transmission?

  1. It increases the resistance of the transmission line
  2. It removes the need for overcurrent protection
  3. It eliminates the need for transformers
  4. It reduces current and therefore reduces line losses for a given power Correct answer.

Explanation

For a fixed power level, raising voltage lowers current, and line loss varies with the square of current. Lower current therefore substantially reduces resistive losses in transmission conductors.

Question 45Laws of Electricity and Electrical Codes

A 15-ampere branch circuit supplies a continuous load. What is the maximum continuous load current permitted under the standard 125 percent sizing rule?

  1. 12 amperes Correct answer.
  2. 15 amperes
  3. 10 amperes
  4. 18.75 amperes

Explanation

Continuous loads must be sized at 125 percent of the load current, so the load itself is limited to the circuit rating divided by 1.25. Dividing 15 amperes by 1.25 gives 12 amperes.

Question 46Laws of Electricity and Electrical Codes

A conductor has a resistance of 2 ohms at a reference temperature. If its temperature coefficient of resistance is positive, what happens to its resistance as temperature rises?

  1. Resistance remains unchanged
  2. Resistance becomes zero
  3. Resistance increases Correct answer.
  4. Resistance decreases

Explanation

Most metals have a positive temperature coefficient, meaning resistance rises as temperature increases. This occurs because increased atomic vibration impedes electron movement.

Question 47Laws of Electricity and Electrical Codes

A 480-volt motor circuit draws 25 amperes at a power factor of 0.85. What is the approximate real power delivered?

  1. 10.2 kilowatts Correct answer.
  2. 8.7 kilowatts
  3. 12.0 kilowatts
  4. 6.0 kilowatts

Explanation

Real power equals voltage times current times power factor. Multiplying 480 volts, 25 amperes, and 0.85 yields approximately 10,200 watts, or 10.2 kilowatts.

Question 48Laws of Electricity and Electrical Codes

Two resistors, 40 ohms and 60 ohms, are connected in parallel across a 120-volt source. What current flows through the 40-ohm resistor?

  1. 5 amperes
  2. 2 amperes
  3. 1.2 amperes
  4. 3 amperes Correct answer.

Explanation

In a parallel circuit, each branch sees the full source voltage. Applying Ohm's law to the 40-ohm branch gives 120 volts divided by 40 ohms, or 3 amperes.

Question 49Laws of Electricity and Electrical Codes

A 120-volt feeder supplies a load 150 feet away using conductors with a total loop resistance of 0.6 ohm. If the load draws 16 amperes, what is the approximate voltage at the load?

  1. 114.4 volts
  2. 120.0 volts
  3. 96.0 volts
  4. 110.4 volts Correct answer.

Explanation

Voltage drop equals current times the total conductor loop resistance, or 16 amperes times 0.6 ohm, giving 9.6 volts. Subtracting 9.6 volts from the 120-volt source leaves approximately 110.4 volts at the load.

Question 50Laws of Electricity and Electrical Codes

A circuit has a resistance of 8 ohms in series with an inductive reactance of 6 ohms. What is the magnitude of the total impedance?

  1. 14 ohms
  2. 2 ohms
  3. 10 ohms Correct answer.
  4. 48 ohms

Explanation

Impedance magnitude in a series resistance-inductance circuit equals the square root of the sum of the resistance squared and reactance squared. The square root of 64 plus 36 equals the square root of 100, or 10 ohms.