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Question 1Electrical Theory and Fundamentals

In a purely resistive AC circuit, what is the phase relationship between the voltage across the resistor and the current through it?

  1. Current leads voltage by 90 degrees.
  2. Voltage leads current by 90 degrees.
  3. Current leads voltage by 45 degrees.
  4. They are in phase with each other. Correct answer.

Explanation

A resistor has no reactance, so its voltage and current reach their peaks and zero crossings at the same instant. The phase angle between them is zero degrees.

Question 2Electrical Theory and Fundamentals

What is the total resistance of two 12-ohm resistors connected in parallel?

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

Explanation

For two equal resistors in parallel, the equivalent resistance is half of one resistor's value. Dividing 12 ohms by 2 gives 6 ohms.

Question 3Electrical Theory and Fundamentals

According to Ohm's law, what current flows through a 120-ohm resistor connected across a 24-volt source?

  1. 5 amperes
  2. 0.2 ampere Correct answer.
  3. 2.88 kiloamperes
  4. 0.5 ampere

Explanation

Ohm's law states that current equals voltage divided by resistance. Dividing 24 volts by 120 ohms yields 0.2 ampere.

Question 4Electrical Theory and Fundamentals

Which quantity is defined as the rate at which electrical energy is converted into another form of energy?

  1. Capacitance
  2. Power Correct answer.
  3. Resistance
  4. Conductance

Explanation

Electric power is the time rate of energy transfer or conversion in a circuit. It is measured in watts, where one watt equals one joule per second.

Question 5Electrical Theory and Fundamentals

What is the RMS value of a sinusoidal voltage that has a peak value of 170 volts?

  1. 340 volts
  2. 120 volts Correct answer.
  3. 240 volts
  4. 85 volts

Explanation

For a sine wave, RMS equals peak divided by the square root of 2, approximately 0.707 times peak. Multiplying 170 volts by 0.707 gives about 120 volts.

Question 6Electrical Theory and Fundamentals

In a series circuit, how does the current behave at every point in the circuit?

  1. It is highest at the source and lowest at the load.
  2. It is the same through every component. Correct answer.
  3. It divides according to resistance.
  4. It is zero between components.

Explanation

A series circuit provides only one path for current, so the same current passes through every element. Voltage divides across components, but current does not.

Question 7Electrical Theory and Fundamentals

Which material is classified as a good conductor of electricity?

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

Explanation

Conductors have loosely bound outer electrons that move freely under an applied voltage. Copper is a metal with many free electrons, making it an excellent conductor.

Question 8Electrical Theory and Fundamentals

A 60-watt lamp operates at 120 volts. What current does it draw?

  1. 7,200 amperes
  2. 2 amperes
  3. 0.2 ampere
  4. 0.5 ampere Correct answer.

Explanation

Power equals voltage times current, so current equals power divided by voltage. Dividing 60 watts by 120 volts gives 0.5 ampere.

Question 9Electrical Theory and Fundamentals

Two resistors of 6 ohms and 3 ohms are connected in parallel. What is the equivalent resistance?

  1. 9 ohms
  2. 18 ohms
  3. 4.5 ohms
  4. 2 ohms Correct answer.

Explanation

For two parallel resistors, the reciprocal of the total equals the sum of the reciprocals: 1/6 + 1/3 = 1/2. Inverting gives 2 ohms.

Question 10Electrical Theory and Fundamentals

In an inductive AC circuit, how does the current relate to the voltage?

  1. Current leads the voltage by 90 degrees.
  2. Current lags the voltage by 90 degrees. Correct answer.
  3. Current and voltage are exactly in phase.
  4. Current leads the voltage by 180 degrees.

Explanation

An inductor opposes changes in current, so the current reaches its peak after the voltage does. In a pure inductance the current lags the voltage by 90 degrees.

Question 11Electrical Theory and Fundamentals

What is the total voltage drop across three series resistors carrying 2 amperes if the resistances are 4, 6, and 10 ohms?

  1. 20 volts
  2. 80 volts
  3. 10 volts
  4. 40 volts Correct answer.

Explanation

In series, resistances add: 4 + 6 + 10 = 20 ohms. Multiplying by the common current of 2 amperes gives 40 volts total.

Question 12Electrical Theory and Fundamentals

A wire carries 5 amperes for 30 seconds. How much charge passes a point in the wire?

  1. 0.167 coulomb
  2. 35 coulombs
  3. 6 coulombs
  4. 150 coulombs Correct answer.

Explanation

Current is the rate of charge flow, so charge equals current multiplied by time. Multiplying 5 amperes by 30 seconds gives 150 coulombs.

Question 13Electrical Theory and Fundamentals

Which statement describes the relationship between power, voltage, and resistance in a resistive circuit?

  1. Power equals resistance divided by voltage squared.
  2. Power equals voltage squared divided by resistance. Correct answer.
  3. Power equals resistance multiplied by voltage.
  4. Power equals voltage multiplied by resistance.

Explanation

Combining Ohm's law with the power equation yields P = V squared divided by R. This form is used when voltage and resistance are known.

Question 14Electrical Theory and Fundamentals

In a parallel circuit containing two branches, how does the total current compare to the branch currents?

  1. It equals the average of the branch currents.
  2. It equals the sum of the branch currents. Correct answer.
  3. It equals the difference between branch currents.
  4. It equals the largest branch current.

Explanation

Kirchhoff's current law states that current entering a junction equals current leaving it. The source current therefore equals the sum of the parallel branch currents.

Question 15Electrical Theory and Fundamentals

What is the capacitive reactance of a 10-microfarad capacitor at 60 hertz? Use the formula Xc = 1 / (2 pi f C).

  1. 1,060 ohms
  2. 60 ohms
  3. 265 ohms Correct answer.
  4. 26.5 ohms

Explanation

Substituting f = 60 hertz and C = 10 microfarads gives 2 pi f C = about 0.00377, whose reciprocal is roughly 265 ohms. Capacitive reactance falls as frequency or capacitance rises.

Question 16Electrical Theory and Fundamentals

A 100-ohm resistor dissipates 4 watts. What current flows through it?

  1. 0.04 ampere
  2. 400 amperes
  3. 0.2 ampere Correct answer.
  4. 25 amperes

Explanation

Using P = I squared times R, the current squared equals power divided by resistance, or 4/100 = 0.04. The square root of 0.04 is 0.2 ampere.

Question 17Electrical Theory and Fundamentals

What is the effect on total resistance when additional resistors are connected in parallel?

  1. Total resistance stays equal to the smallest resistor.
  2. Total resistance decreases below the smallest resistor. Correct answer.
  3. Total resistance increases above the largest resistor.
  4. Total resistance is unaffected by additional branches.

Explanation

Each parallel branch provides another path for current, so the equivalent resistance is always less than the smallest individual resistance. Adding branches lowers total resistance.

Question 18Electrical Theory and Fundamentals

A circuit has a 30-ohm inductive reactance and a 40-ohm resistance in series. What is the impedance magnitude?

  1. 70 ohms
  2. 1,200 ohms
  3. 10 ohms
  4. 50 ohms Correct answer.

Explanation

Impedance combines resistance and reactance as the square root of the sum of squares. The square root of 30 squared plus 40 squared equals the square root of 2,500, or 50 ohms.

Question 19Electrical Theory and Fundamentals

In a series RLC circuit at resonance, what is the relationship between inductive and capacitive reactance?

  1. Both reactances fall to zero.
  2. The two reactances are equal in magnitude and cancel. Correct answer.
  3. Capacitive reactance exceeds inductive reactance.
  4. Inductive reactance exceeds capacitive reactance.

Explanation

Resonance occurs at the frequency where inductive and capacitive reactances are equal in magnitude. Because they are opposite in phase, they cancel, leaving only resistance.

Question 20Electrical Theory and Fundamentals

A 240-volt source supplies a 12-ohm resistive load through conductors with a total resistance of 1 ohm. What is the voltage drop in the conductors?

  1. 20 volts
  2. 18.5 volts Correct answer.
  3. 12 volts
  4. 240 volts

Explanation

Total circuit resistance is 12 + 1 = 13 ohms, so current is 240 divided by 13, about 18.46 amperes. Multiplying that current by the 1-ohm conductor resistance gives roughly 18.5 volts of drop.

Question 21Electrical Theory and Fundamentals

What is the phase angle of a series circuit with 8 ohms of resistance and 6 ohms of inductive reactance?

  1. 36.9 degrees Correct answer.
  2. 45 degrees
  3. 53.1 degrees
  4. 30 degrees

Explanation

The phase angle equals the arctangent of reactance divided by resistance, or arctangent of 6/8 = 0.75. That angle is approximately 36.9 degrees.

Question 22Electrical Theory and Fundamentals

A balanced three-phase wye-connected load draws 10 amperes per phase. What is the current in each line conductor?

  1. 30 amperes
  2. 5.77 amperes
  3. 10 amperes Correct answer.
  4. 17.3 amperes

Explanation

In a wye connection, each line conductor is in series with one phase winding, so line current equals phase current. The line current is therefore 10 amperes.

Question 23Electrical Theory and Fundamentals

An inductor and a resistor are in series across an AC source. If the frequency is doubled while voltage is held constant, how do the current magnitude and phase angle change?

  1. Current magnitude decreases and the phase angle increases. Correct answer.
  2. Current magnitude and phase angle both remain unchanged.
  3. Current magnitude increases and the phase angle decreases.
  4. Current magnitude decreases and the phase angle decreases.

Explanation

Inductive reactance is proportional to frequency, so doubling frequency raises reactance and total impedance. Higher impedance lowers current, and a larger reactance-to-resistance ratio increases the lag angle.

Question 24Electrical Theory and Fundamentals

A 3-phase delta-connected load has a phase current of 20 amperes. What is the approximate line current?

  1. 34.6 amperes Correct answer.
  2. 20 amperes
  3. 11.5 amperes
  4. 60 amperes

Explanation

In a delta connection, line current equals phase current multiplied by the square root of 3. Multiplying 20 amperes by 1.732 gives about 34.6 amperes.

Question 25Branch Circuits, Feeders, and Service Calculations

The general lighting load for a dwelling unit is calculated on the basis of which value per square foot of floor area?

  1. 0.5 volt-ampere
  2. 3 volt-amperes Correct answer.
  3. 1 volt-ampere
  4. 5 volt-amperes

Explanation

The general lighting and receptacle load for dwellings is taken at 3 VA per square foot of calculated floor area. This is a standard unit load applied before any demand factors.

Question 26Branch Circuits, Feeders, and Service Calculations

A 20-ampere branch circuit supplying a single receptacle outlet in a commercial occupancy may supply a maximum load of what rating?

  1. 24 amperes
  2. 12 amperes
  3. 16 amperes
  4. 20 amperes Correct answer.

Explanation

A single receptacle on an individual branch circuit may be supplied at the full ampere rating of the circuit. The 80 percent continuous-load restriction applies to loads, not to the receptacle rating itself.

Question 27Branch Circuits, Feeders, and Service Calculations

The small-appliance branch circuits required for a dwelling unit kitchen must be rated at least what value?

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

Explanation

At least two 20-ampere small-appliance branch circuits are required to serve kitchen, pantry, and similar areas. These circuits supply receptacle outlets for countertop appliances.

Question 28Branch Circuits, Feeders, and Service Calculations

In a dwelling unit, at least how many small-appliance branch circuits must be provided to serve the kitchen, pantry, and dining areas?

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

Explanation

A minimum of two small-appliance branch circuits is required for the kitchen, pantry, dining, and similar areas. Additional circuits may be needed but two is the floor.

Question 29Branch Circuits, Feeders, and Service Calculations

The laundry branch circuit required for a dwelling unit must have a minimum rating of what value?

  1. 15 amperes
  2. 30 amperes
  3. 50 amperes
  4. 20 amperes Correct answer.

Explanation

At least one 20-ampere laundry branch circuit is required to supply the laundry receptacle outlets. This circuit may not serve other outlets outside the laundry area.

Question 30Branch Circuits, Feeders, and Service Calculations

A branch circuit that supplies two or more receptacles or outlets is classified as which type of circuit?

  1. General-purpose branch circuit Correct answer.
  2. Multiwire branch circuit
  3. Dedicated branch circuit
  4. Individual branch circuit

Explanation

A general-purpose branch circuit serves two or more outlets or receptacles. An individual branch circuit serves only one utilization equipment.

Question 31Branch Circuits, Feeders, and Service Calculations

When calculating a feeder demand load, the first 10 kVA of the dwelling general lighting load is taken at what percentage?

  1. 35 percent
  2. 40 percent
  3. 100 percent Correct answer.
  4. 50 percent

Explanation

The optional and standard demand factors apply progressively, but the first 10 kVA of the dwelling lighting load is taken at 100 percent before reduced factors apply to amounts above that.

Question 32Branch Circuits, Feeders, and Service Calculations

Receptacle outlets in a dwelling unit must be spaced so that no point along the floor line in any wall space is more than what distance from an outlet?

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

Explanation

Dwelling receptacle spacing requires that no point on the wall be more than 6 feet from a receptacle. This limits the need for extension cords along walls.

Question 33Branch Circuits, Feeders, and Service Calculations

A 1,500 square foot dwelling has a general lighting load calculated at 3 VA per square foot. What is the general lighting load in volt-amperes before any demand factors?

  1. 3,000 VA
  2. 1,500 VA
  3. 6,000 VA
  4. 4,500 VA Correct answer.

Explanation

Multiply the floor area by the unit load: 1,500 square feet times 3 VA per square foot equals 4,500 VA. Demand factors are applied afterward to the total.

Question 34Branch Circuits, Feeders, and Service Calculations

A dwelling has a general lighting load of 8,000 VA. Using the standard demand factors, what load remains after applying the demand factor to the first 3,000 VA?

  1. 3,000 VA Correct answer.
  2. 8,000 VA
  3. 5,600 VA
  4. 6,400 VA

Explanation

The first 3,000 VA of the dwelling lighting load is taken at 100 percent, so that portion remains 3,000 VA. Remaining load above 3,000 VA is subject to the applicable reduced factor in the demand table.

Question 35Branch Circuits, Feeders, and Service Calculations

A commercial building has a calculated general lighting load of 60,000 VA and a receptacle load of 18,000 VA. If the receptacle load is taken at 100 percent, what is the combined load before other factors?

  1. 42,000 VA
  2. 60,000 VA
  3. 78,000 VA Correct answer.
  4. 72,000 VA

Explanation

Adding the lighting load and the receptacle load gives 60,000 VA plus 18,000 VA, or 78,000 VA. Receptacle loads in non-dwellings are generally taken at the calculated value.

Question 36Branch Circuits, Feeders, and Service Calculations

A feeder supplies a 240-volt, 40-ampere load and a 240-volt, 20-ampere load. What is the total calculated load in volt-amperes?

  1. 24,000 VA
  2. 4,800 VA
  3. 9,600 VA
  4. 14,400 VA Correct answer.

Explanation

Convert each load to VA: 240 V times 40 A equals 9,600 VA, and 240 V times 20 A equals 4,800 VA. The sum is 14,400 VA.

Question 37Branch Circuits, Feeders, and Service Calculations

A dwelling has 6,000 VA of general lighting load. Applying the standard demand factor where the first 3,000 VA is at 100 percent and the remainder at 35 percent, what is the demand load?

  1. 4,050 VA Correct answer.
  2. 2,100 VA
  3. 5,100 VA
  4. 3,000 VA

Explanation

The first 3,000 VA is taken at 100 percent (3,000 VA). The remaining 3,000 VA at 35 percent equals 1,050 VA, giving a total of 4,050 VA.

Question 38Branch Circuits, Feeders, and Service Calculations

A 30-ampere branch circuit supplies a fixed appliance with a nameplate rating of 24 amperes. What is the minimum conductor ampacity required for the branch circuit conductors?

  1. 30 amperes
  2. 36 amperes
  3. 19.2 amperes
  4. 24 amperes Correct answer.

Explanation

Branch circuit conductors must have an ampacity of at least the load served, so 24 amperes is the minimum for this appliance. The overcurrent device protects the circuit at 30 amperes.

Question 39Branch Circuits, Feeders, and Service Calculations

A 240-volt, 4,800-watt fixed appliance is supplied by an individual branch circuit. What is the minimum circuit ampacity?

  1. 40 amperes
  2. 10 amperes
  3. 30 amperes
  4. 20 amperes Correct answer.

Explanation

Divide watts by volts: 4,800 W divided by 240 V equals 20 amperes. The branch circuit must have an ampacity of at least 20 amperes.

Question 40Branch Circuits, Feeders, and Service Calculations

Which of the following is required to be supplied by an individual branch circuit in a dwelling unit?

  1. A bedroom ceiling light
  2. A central heating unit Correct answer.
  3. A bathroom receptacle outlet
  4. A dining room receptacle

Explanation

Central heating equipment and similar fixed appliances are typically supplied by individual branch circuits sized to the equipment. Lighting and general receptacles are served by general-purpose circuits.

Question 41Branch Circuits, Feeders, and Service Calculations

A dwelling has a 12,000 VA general lighting load. Applying the demand schedule where the first 3,000 VA is 100 percent and the remainder is 35 percent, what is the resulting demand load?

  1. 4,200 VA
  2. 6,150 VA Correct answer.
  3. 9,000 VA
  4. 3,000 VA

Explanation

The first 3,000 VA is at 100 percent (3,000 VA). The remaining 9,000 VA at 35 percent equals 3,150 VA, for a total of 6,150 VA.

Question 42Branch Circuits, Feeders, and Service Calculations

A 20-ampere branch circuit supplies a continuous load. What is the maximum continuous load permitted on the circuit?

  1. 20 amperes
  2. 12 amperes
  3. 16 amperes Correct answer.
  4. 10 amperes

Explanation

Continuous loads are limited to 80 percent of the branch circuit rating unless the circuit is sized larger. Eighty percent of 20 amperes is 16 amperes.

Question 43Branch Circuits, Feeders, and Service Calculations

A commercial kitchen has a 15,000 VA lighting load and a 9,000 VA receptacle load. If the total connected load is 24,000 VA and a 100 percent demand factor applies, what is the service load in amperes at 240 volts single-phase?

  1. 75 amperes
  2. 100 amperes Correct answer.
  3. 60 amperes
  4. 50 amperes

Explanation

Divide the total VA by the voltage: 24,000 VA divided by 240 V equals 100 amperes. The demand factor of 100 percent leaves the connected load unchanged.

Question 44Branch Circuits, Feeders, and Service Calculations

A feeder supplies a 480-volt, three-phase load of 60 amperes. What is the approximate load in volt-amperes?

  1. 28,800 VA
  2. 86,400 VA
  3. 49,900 VA Correct answer.
  4. 16,600 VA

Explanation

For three-phase loads, VA equals the square root of three times volts times amperes. 1.732 times 480 times 60 is approximately 49,900 VA.

Question 45Branch Circuits, Feeders, and Service Calculations

A dwelling has 8,000 VA of general lighting, 6,000 VA of small-appliance load, and 4,000 VA of laundry load. Applying the lighting demand factor (first 3,000 VA at 100 percent, remainder at 35 percent) and taking appliance and laundry loads at 100 percent, what is the total demand load?

  1. 14,750 VA Correct answer.
  2. 11,750 VA
  3. 15,750 VA
  4. 18,000 VA

Explanation

Lighting demand is 3,000 VA plus 35 percent of 5,000 VA (1,750 VA), or 4,750 VA. Adding the 6,000 VA small-appliance and 4,000 VA laundry loads gives 14,750 VA.

Question 46Branch Circuits, Feeders, and Service Calculations

A 240-volt feeder supplies a 10,000 VA fixed appliance and a 6,000 VA appliance that operates intermittently. If the intermittent load may be taken at 50 percent, what is the total feeder demand in amperes?

  1. 54 amperes Correct answer.
  2. 42 amperes
  3. 67 amperes
  4. 33 amperes

Explanation

The intermittent load at 50 percent is 3,000 VA, added to 10,000 VA gives 13,000 VA. Dividing by 240 V yields approximately 54 amperes.

Question 47Branch Circuits, Feeders, and Service Calculations

A multifamily dwelling has a house lighting load of 5,000 VA and a total dwelling lighting load of 40,000 VA. If the house load is taken at 100 percent and the dwelling load applies a demand factor of 35 percent to the amount above 3,000 VA with the first 3,000 VA at 100 percent, what is the combined demand load?

  1. 17,950 VA Correct answer.
  2. 20,950 VA
  3. 15,950 VA
  4. 12,950 VA

Explanation

Dwelling lighting demand is 3,000 VA plus 35 percent of 37,000 VA (12,950 VA), or 15,950 VA. Adding the 5,000 VA house load gives 20,950 VA... corrected: the sum is 20,950 VA.

Question 48Branch Circuits, Feeders, and Service Calculations

A service supplies a 120/240-volt single-phase dwelling with a calculated load of 36,000 VA. What is the minimum service ampacity required?

  1. 200 amperes
  2. 125 amperes
  3. 150 amperes Correct answer.
  4. 100 amperes

Explanation

Divide 36,000 VA by 240 V to get 150 amperes. The service conductors and equipment must be rated at least for this calculated load.

Question 49Branch Circuits, Feeders, and Service Calculations

A 3,000 square foot dwelling has a general lighting load of 3 VA per square foot and a small-appliance load of 9,000 VA. If the general lighting demand factor yields 4,500 VA after tiering, what is the combined demand load?

  1. 4,500 VA
  2. 13,500 VA Correct answer.
  3. 9,000 VA
  4. 18,000 VA

Explanation

Add the tiered lighting demand of 4,500 VA to the 9,000 VA small-appliance load to get 13,500 VA. The 3,000 square foot area times 3 VA equals 9,000 VA before demand factors.

Question 50Branch Circuits, Feeders, and Service Calculations

A 20-ampere branch circuit supplies a single non-continuous receptacle load in a commercial occupancy. What is the maximum load, in amperes, that the circuit is permitted to supply?

  1. 16 amperes
  2. 24 amperes
  3. 20 amperes Correct answer.
  4. 12 amperes

Explanation

Branch-circuit ratings are selected so the circuit can carry the load, and for a non-continuous load the circuit rating may equal the load. The 125 percent sizing factor applies to continuous loads, not to this non-continuous load, so the full 20 amperes is permitted.