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MN Journeyman Electrician practice questions

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Question 1General Electrical Knowledge and Theory

In a purely resistive AC circuit, how do the voltage and current waveforms relate to each other?

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

Explanation

Resistance dissipates energy without storing it, so the current through a resistor rises and falls exactly in step with the voltage across it. The phase angle is zero, giving a power factor of unity. Inductance and capacitance are what shift current out of phase, not resistance.

Question 2General Electrical Knowledge and Theory

A 12-gauge copper conductor has a resistance of 1.93 ohms per 1,000 feet. What is the approximate voltage drop on a 120-foot run carrying 16 amperes?

  1. 14.8 volts
  2. 3.7 volts Correct answer.
  3. 7.4 volts
  4. 1.9 volts

Explanation

The conductor resistance is 1.93 ohms x 120/1,000 = 0.2316 ohm, and voltage drop is I x R = 16 x 0.2316 = 3.7 volts for a single conductor length. A complete circuit involves two conductors, which doubles the drop to about 7.4 volts; the question asks for the drop on the stated run of one conductor length.

Question 3General Electrical Knowledge and Theory

Which statement correctly describes the relationship among voltage, current, and resistance in a DC circuit?

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

Explanation

Ohm's law states that the voltage across a resistive element equals the product of the current through it and its resistance, written E = I x R. Rearranged, current is voltage divided by resistance and resistance is voltage divided by current. Power is a separate relationship, P = E x I.

Question 4General Electrical Knowledge and Theory

A 240-volt single-phase load draws 30 amperes. What is the apparent power of the load?

  1. 8.0 kVA
  2. 2.4 kVA
  3. 7.2 kVA Correct answer.
  4. 4.0 kVA

Explanation

Apparent power in a single-phase circuit is voltage times current, S = E x I = 240 x 30 = 7,200 volt-amperes, or 7.2 kVA. Apparent power is stated in volt-amperes regardless of the power factor. Real power in watts would require multiplying by the power factor.

Question 5General Electrical Knowledge and Theory

A three-phase, 480-volt motor draws a line current of 50 amperes at a power factor of 0.85. What is the real power consumed by the motor?

  1. 40.8 kW
  2. 24.5 kW
  3. 20.4 kW
  4. 35.3 kW Correct answer.

Explanation

Real power in a balanced three-phase circuit is P = 1.732 x E x I x power factor. Substituting: 1.732 x 480 x 50 x 0.85 = 35,333 watts, about 35.3 kW. Omitting the power factor gives apparent power in kVA instead of real power in kW.

Question 6General Electrical Knowledge and Theory

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

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

Explanation

A series circuit provides only one path for electrons, so the same current must flow through every element. The voltage divides among the resistors in proportion to their resistance values. Power also varies with each resistor's resistance.

Question 7General Electrical Knowledge and Theory

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

  1. 0.5 ohm
  2. 2 ohms Correct answer.
  3. 9 ohms
  4. 4.5 ohms

Explanation

For two resistors in parallel, the equivalent resistance is the product divided by the sum: (6 x 3)/(6 + 3) = 18/9 = 2 ohms. The result is always smaller than the smallest individual resistance. Adding resistances directly applies only to series circuits.

Question 8General Electrical Knowledge and Theory

What is the total capacitance of a 4-microfarad and a 12-microfarad capacitor connected in parallel?

  1. 8 microfarads
  2. 16 microfarads Correct answer.
  3. 48 microfarads
  4. 3 microfarads

Explanation

Capacitors in parallel add directly because their plates are effectively joined, increasing total plate area: 4 + 12 = 16 microfarads. This is the opposite of resistors, which add directly in series. The reciprocal formula applies to capacitors in series.

Question 9General Electrical Knowledge and Theory

An inductor opposes any change in the current flowing through it. This property is known as:

  1. Inductive reactance
  2. Conductance
  3. Capacitive reactance
  4. Self-inductance Correct answer.

Explanation

Self-inductance is the property of a coil that induces a counter-electromotive force opposing changes in its own current. Inductive reactance is the opposition to steady alternating current expressed in ohms, which is a related but distinct quantity. The counter-emf follows Lenz's law.

Question 10General Electrical Knowledge and Theory

A circuit has 8 ohms of resistance and 6 ohms of inductive reactance in series. What is the impedance?

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

Explanation

Impedance in an R-L series circuit is the vector sum of resistance and reactance: Z = square root of (R squared + X squared) = square root of (64 + 36) = 10 ohms. Resistance and reactance are 90 degrees out of phase, so they cannot be added arithmetically. The phase angle would be the arctangent of 6/8.

Question 11General Electrical Knowledge and Theory

A transformer has 500 turns on the primary and 50 turns on the secondary. If the primary is supplied at 480 volts, what is the secondary voltage?

  1. 240 volts
  2. 48 volts Correct answer.
  3. 4,800 volts
  4. 96 volts

Explanation

The turns ratio is 500:50, or 10:1, so the secondary voltage is 480 divided by 10, or 48 volts. A step-down transformer reduces voltage in proportion to the turns ratio. Current increases by the same ratio while power remains essentially constant.

Question 12General Electrical Knowledge and Theory

A transformer with a 10:1 turns ratio has a secondary current of 60 amperes. What is the primary current, neglecting losses?

  1. 6 amperes Correct answer.
  2. 60 amperes
  3. 600 amperes
  4. 0.6 ampere

Explanation

In an ideal transformer, power in equals power out, so the current ratio is the inverse of the voltage ratio. With a 10:1 step-down ratio, the primary current is 60 divided by 10, or 6 amperes. The primary carries less current at higher voltage for the same power.

Question 13General Electrical Knowledge and Theory

A 120-volt circuit has a 15-ampere circuit breaker. What is the maximum continuous load permitted on the circuit under the general 80 percent rule?

  1. 12 amperes Correct answer.
  2. 10 amperes
  3. 18 amperes
  4. 15 amperes

Explanation

Continuous loads are limited to 80 percent of the overcurrent device rating, so 15 x 0.80 = 12 amperes. A continuous load operates for three hours or more. Loading a breaker to its full rating continuously risks nuisance tripping from conductor heating.

Question 14General Electrical Knowledge and Theory

How much power is dissipated in a 10-ohm resistor carrying 4 amperes?

  1. 40 watts
  2. 160 watts Correct answer.
  3. 2.5 watts
  4. 80 watts

Explanation

Power in a resistive element is P = I squared x R = 4 x 4 x 10 = 160 watts. The squared current term means doubling current quadruples the heating. This relationship explains why overloaded conductors heat so rapidly.

Question 15General Electrical Knowledge and Theory

Which of these describes the current that flows when a capacitor is connected to a DC source after the initial charging period?

  1. It falls to essentially zero Correct answer.
  2. It rises steadily with time
  3. It continues at a steady value
  4. It reverses direction periodically

Explanation

Once a capacitor charges to the source voltage, no further electron flow occurs in the DC circuit, so current falls to essentially zero. The charging current decays exponentially during the transient period. A capacitor blocks steady DC while passing changing signals.

Question 16General Electrical Knowledge and Theory

A conductor carrying alternating current experiences increased effective resistance because current concentrates near the conductor surface. What is this effect called?

  1. Hysteresis
  2. Corona
  3. Skin effect Correct answer.
  4. Eddy current loss

Explanation

Skin effect is the tendency of alternating current to crowd toward the outer surface of a conductor, reducing the effective cross section and raising resistance. It becomes more pronounced at higher frequencies. This is why large conductors are sometimes replaced with multiple smaller strands in high-frequency work.

Question 17General Electrical Knowledge and Theory

A 3-phase, 4-wire, 208Y/120-volt system supplies a balanced wye-connected load. What is the line-to-neutral voltage?

  1. 360 volts
  2. 208 volts
  3. 104 volts
  4. 120 volts Correct answer.

Explanation

In a wye system, the line-to-neutral voltage equals the line-to-line voltage divided by the square root of three: 208 / 1.732 = 120 volts. This is why the system is designated 208Y/120. The neutral point provides the lower voltage for line-to-neutral loads.

Question 18General Electrical Knowledge and Theory

In a 3-phase delta system, how are the windings connected?

  1. Windings are connected in series with the load
  2. The windings form a closed loop with each corner connected to a phase conductor Correct answer.
  3. Each winding connects between a phase conductor and the neutral
  4. All windings share a common center point

Explanation

A delta connection joins the three windings end to end in a closed loop, and each junction serves as a phase terminal. There is no neutral point, so line-to-neutral voltage is not directly available. A wye connection, by contrast, joins one end of each winding at a common neutral.

Question 19General Electrical Knowledge and Theory

A 60-hertz alternating current completes how many full cycles in one second?

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

Explanation

Frequency in hertz is defined as cycles per second, so 60 hertz means 60 complete cycles each second. Each cycle includes one positive and one negative alternation. The period of one cycle at 60 hertz is about 16.7 milliseconds.

Question 20General Electrical Knowledge and Theory

What is the period of one complete cycle of a 50-hertz waveform?

  1. 2 milliseconds
  2. 500 milliseconds
  3. 50 milliseconds
  4. 20 milliseconds Correct answer.

Explanation

Period is the reciprocal of frequency: T = 1/f = 1/50 = 0.02 second, or 20 milliseconds. Period and frequency are inversely related. A higher frequency shortens the period proportionally.

Question 21General Electrical Knowledge and Theory

A 25-ohm resistor and a 25-ohm capacitive reactance are in series across a 100-volt source. What is the power factor of the circuit?

  1. 0.25
  2. 0.707 Correct answer.
  3. 0.50
  4. 1.0

Explanation

When resistance equals capacitive reactance, the phase angle is 45 degrees, and the power factor is the cosine of 45 degrees, or 0.707. The power factor is always the cosine of the angle between voltage and current. Equal R and X values produce this classic 45-degree result.

Question 22General Electrical Knowledge and Theory

Which condition produces resonance in a series RLC circuit?

  1. Capacitive reactance is twice the inductive reactance
  2. Resistance exceeds total reactance
  3. Resistance equals impedance
  4. Inductive reactance equals capacitive reactance Correct answer.

Explanation

Series resonance occurs when inductive reactance and capacitive reactance are equal in magnitude, so they cancel and the circuit impedance reduces to resistance alone. At that point current is at maximum for a given voltage. The resonant frequency depends on inductance and capacitance.

Question 23General Electrical Knowledge and Theory

A wye-connected load has a phase voltage of 277 volts and a phase current of 20 amperes at unity power factor. What is the total three-phase real power?

  1. 2.77 kW
  2. 16.6 kW Correct answer.
  3. 9.6 kW
  4. 5.54 kW

Explanation

Total three-phase power equals three times the phase power: 3 x 277 x 20 x 1.0 = 16,620 watts, about 16.6 kW. Because the load is wye-connected, phase voltage and phase current can be used directly with the factor of three. Using line voltage with the square-root-of-three factor gives the same result.

Question 24General Electrical Knowledge and Theory

What happens to the total resistance of a circuit when an additional resistor is connected in parallel with an existing resistor?

  1. Total resistance doubles
  2. Total resistance increases
  3. Total resistance remains the same
  4. Total resistance decreases Correct answer.

Explanation

Adding a parallel path gives current another route, so the equivalent resistance always falls below the smallest branch resistance. Each added branch increases total conductance. This is why parallel circuits draw more current as more loads are energized.

Question 25General Electrical Knowledge and Theory

A 1,000-watt load operates for 8 hours each day. At 12 cents per kilowatt-hour, what is the daily energy cost?

  1. $1.20
  2. $9.60
  3. $0.12
  4. $0.96 Correct answer.

Explanation

Energy equals power times time: 1 kW x 8 hours = 8 kWh per day. Multiplying by 12 cents per kWh gives $0.96. Billing is based on kilowatt-hours, not instantaneous watts.

Question 26General Electrical Knowledge and Theory

According to Ohm's law, what current flows through a 24-ohm resistive heating element connected across a 240-volt supply?

  1. 0.5 ampere
  2. 5,760 amperes
  3. 0.1 ampere
  4. 10 amperes Correct answer.

Explanation

Ohm's law states that current equals voltage divided by resistance (I = E/R). Dividing 240 volts by 24 ohms gives 10 amperes. This relationship holds for a purely resistive load at a steady state.

Question 27General Electrical Knowledge and Theory

A 120-volt branch circuit supplies a single resistive load that draws 12 amperes. What is the resistance of the load?

  1. 132 ohms
  2. 10 ohms Correct answer.
  3. 0.1 ohm
  4. 1,440 ohms

Explanation

Resistance is found by rearranging Ohm's law to R = E/I. Dividing 120 volts by 12 amperes yields 10 ohms. The resistive nature of the load means no reactance needs to be considered.

Question 28General Electrical Knowledge and Theory

In a purely inductive AC circuit, how does the current relate to the applied voltage?

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

Explanation

An inductor opposes changes in current, so in a purely inductive circuit the current reaches its peak one quarter cycle after the voltage. This corresponds to the current lagging the voltage by 90 electrical degrees.

Question 29General Electrical Knowledge and Theory

How much energy does a 1,500-watt appliance consume when operated for 4 hours?

  1. 6 kilowatt-hours Correct answer.
  2. 1.5 kilowatt-hours
  3. 6,000 kilowatt-hours
  4. 375 kilowatt-hours

Explanation

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

Question 30General Electrical Knowledge and Theory

Which instrument connection is used to measure the current through a branch circuit?

  1. A voltmeter connected in parallel with the branch
  2. An ohmmeter connected across the de-energized branch
  3. An ammeter connected in series with the branch Correct answer.
  4. A wattmeter connected only to the grounded conductor

Explanation

Current must pass through the measuring element, so an ammeter is connected in series with the conductor carrying the branch current. Connecting it in parallel would place a low-resistance path across the source and can cause a short circuit.

Question 31General Electrical Knowledge and Theory

What is the standard relationship between frequency and period for an AC waveform?

  1. Frequency equals twice the period.
  2. Period equals the reciprocal of frequency. Correct answer.
  3. Period equals frequency squared.
  4. Frequency and period are independent quantities.

Explanation

Period is the time for one complete cycle, and frequency is the number of cycles per second. Because these are inverse quantities, period equals one divided by frequency.

Question 32General Electrical Knowledge and Theory

What is the total power in a single-phase 240-volt circuit carrying 20 amperes at unity power factor?

  1. 4,800 watts Correct answer.
  2. 240 watts
  3. 12 watts
  4. 1,200 watts

Explanation

For a single-phase circuit, true power equals voltage times current times the power factor. With unity power factor, 240 volts times 20 amperes gives 4,800 watts.

Question 33General Electrical Knowledge and Theory

Which material is classified as a conductor because it has many free electrons available to carry current?

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

Explanation

Metals such as copper have loosely bound outer electrons that move readily under an applied voltage, making them good conductors. Materials with tightly bound electrons, such as rubber and glass, resist current flow.

Question 34General Electrical Knowledge and Theory

A 480-volt, 3-phase motor draws a line current of 25 amperes at a power factor of 0.85. What is the approximate input power?

  1. 30,000 watts
  2. 10,200 watts
  3. 17,674 watts Correct answer.
  4. 12,000 watts

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 25 amperes by 0.85 gives approximately 17,674 watts.

Question 35General Electrical Knowledge and Theory

Two parallel branch circuits each carry 15 amperes and are supplied by a common feeder. What current flows in the feeder?

  1. 15 amperes
  2. 30 amperes Correct answer.
  3. 7.5 amperes
  4. 225 amperes

Explanation

In a parallel circuit, branch currents add at the common junction, so the feeder carries the sum of the branch currents. Adding 15 amperes and 15 amperes gives 30 amperes.

Question 36General Electrical Knowledge and Theory

A circuit contains a 30-ohm resistor in series with a 40-ohm inductive reactance. What is the impedance?

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

Explanation

Impedance in a series RL circuit is the square root of the sum of the resistance squared and the reactance squared. The square root of 900 plus 1,600 is the square root of 2,500, which is 50 ohms.

Question 37General Electrical Knowledge and Theory

How does the total capacitance of capacitors connected in series compare with the individual capacitances?

  1. The total is the sum of all capacitances.
  2. The total is less than the smallest capacitance. Correct answer.
  3. The total is greater than the largest capacitance.
  4. The total is always zero.

Explanation

Series capacitors combine like parallel resistors, using the reciprocal of the sum of reciprocals. The resulting equivalent capacitance is always smaller than the smallest individual capacitor in the series string.

Question 38General Electrical Knowledge and Theory

A transformer has a primary of 240 turns and a secondary of 60 turns. If the secondary voltage is 120 volts, what is the primary voltage?

  1. 120 volts
  2. 240 volts
  3. 480 volts Correct answer.
  4. 30 volts

Explanation

Voltage ratio equals turns ratio, so primary voltage divided by secondary voltage equals primary turns divided by secondary turns. The 4:1 turns ratio times 120 volts secondary gives 480 volts primary.

Question 39General Electrical Knowledge and Theory

In a series circuit, how does the total voltage divide among components with different resistances?

  1. Only across the largest resistance
  2. Directly proportional to resistance Correct answer.
  3. Inversely proportional to resistance
  4. Equally among all components regardless of resistance

Explanation

Because the same current flows through each series element, the voltage drop across each equals current times its resistance. Greater resistance therefore produces a proportionally greater voltage drop.

Question 40General Electrical Knowledge and Theory

What is the root-mean-square value of a sinusoidal voltage whose peak value is 170 volts?

  1. 120 volts Correct answer.
  2. 340 volts
  3. 170 volts
  4. 85 volts

Explanation

The RMS value of a sine wave equals the peak value divided by the square root of two, or multiplied by about 0.707. Applying 0.707 to 170 volts gives approximately 120 volts.

Question 41General Electrical Knowledge and Theory

A 120-volt circuit has a load of 1,800 volt-amperes. What is the current drawn by the load?

  1. 15 amperes Correct answer.
  2. 216,000 amperes
  3. 10 amperes
  4. 20 amperes

Explanation

Apparent power in volt-amperes equals voltage times current for a single-phase circuit. Dividing 1,800 volt-amperes by 120 volts yields 15 amperes.

Question 42General Electrical Knowledge and Theory

A 3-phase, 480-volt motor draws 40 amperes per phase with a power factor of 0.8. What is the approximate apparent power?

  1. 41,569 volt-amperes
  2. 19,200 volt-amperes
  3. 33,255 volt-amperes Correct answer.
  4. 8,314 volt-amperes

Explanation

Apparent power in a three-phase circuit equals the square root of three times line voltage times line current. Multiplying 1.732 by 480 volts by 40 amperes gives approximately 33,255 volt-amperes.

Question 43General Electrical Knowledge and Theory

Which effect explains why the current through an inductor cannot change instantaneously?

  1. The inductor stores energy in an electrostatic field.
  2. Inductive reactance increases with frequency.
  3. The inductor has zero resistance at DC.
  4. The inductor stores energy in a magnetic field that opposes changes in current. Correct answer.

Explanation

Current through an inductor creates a magnetic field, and the inductor opposes any change in that field by inducing a counter voltage. This self-induced voltage limits how quickly the current can change.

Question 44General Electrical Knowledge and Theory

What is the power factor of a circuit with 8 ohms of resistance and 6 ohms of capacitive reactance in series?

  1. 0.6
  2. 0.8 Correct answer.
  3. 1.0
  4. 0.75

Explanation

Impedance is the square root of 64 plus 36, which is 10 ohms. Power factor equals resistance divided by impedance, so 8 divided by 10 gives 0.8.

Question 45General Electrical Knowledge and Theory

A single-phase 120-volt circuit has a 20-ampere continuous load. Applying the 80 percent continuous-load rule, what minimum overcurrent device rating is required?

  1. 16 amperes
  2. 20 amperes
  3. 25 amperes Correct answer.
  4. 30 amperes

Explanation

Continuous loads must be limited to 80 percent of the overcurrent device rating, so the device rating must be at least the load divided by 0.8. Dividing 20 amperes by 0.8 gives 25 amperes.

Question 46General Electrical Knowledge and Theory

A series circuit has a 100-ohm resistor, a 60-ohm inductive reactance, and an 80-ohm capacitive reactance. What is the total impedance?

  1. 100 ohms Correct answer.
  2. 120 ohms
  3. 80 ohms
  4. 240 ohms

Explanation

Net reactance is the difference between inductive and capacitive reactance, giving 20 ohms of capacitive reactance. Impedance is the square root of 100 squared plus 20 squared, approximately 102 ohms, which rounds to 100 ohms among the choices.

Question 47General Electrical Knowledge and Theory

A wye-connected load has a phase voltage of 277 volts and a phase current of 20 amperes at unity power factor. What is the total three-phase power?

  1. 27,700 watts
  2. 16,620 watts
  3. 9,594 watts Correct answer.
  4. 5,540 watts

Explanation

Total three-phase power equals three times phase voltage times phase current times power factor. Three times 277 volts times 20 amperes gives approximately 16,620 watts, but since the load is wye, line voltage is 480 volts and the standard formula yields about 9,594 watts only if phase values are misapplied.

Question 48General Electrical Knowledge and Theory

A 3-phase, 4-wire, 480Y/277-volt system supplies a balanced wye load. What is the line-to-line voltage?

  1. 277 volts
  2. 831 volts
  3. 160 volts
  4. 480 volts Correct answer.

Explanation

In a wye system, line-to-line voltage equals the line-to-neutral voltage multiplied by the square root of three. Multiplying 277 volts by 1.732 gives approximately 480 volts.

Question 49General Electrical Knowledge and Theory

A transformer bank supplies a 480-volt, 3-phase load of 100 kilovolt-amperes. What is the approximate line current?

  1. 60 amperes
  2. 120 amperes Correct answer.
  3. 208 amperes
  4. 83 amperes

Explanation

Three-phase line current equals apparent power divided by the square root of three times line voltage. Dividing 100,000 volt-amperes by 831 volts gives approximately 120 amperes.

Question 50General Electrical Knowledge and Theory

In a series circuit, which quantity remains the same through every component?

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

Explanation

A series circuit provides only one path for electrons, so the same current flows through every element. Voltage and power may differ across components depending on their individual resistances.