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IA Electrician practice questions

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Question 1Electrical Theory and Principles

A 120 V source is connected across a 15 Ω resistor. What current flows through the resistor?

  1. 135 A
  2. 1800 A
  3. 0.125 A
  4. 8 A Correct answer.

Explanation

Ohm's law states that current equals voltage divided by resistance (I = V/R). Dividing 120 V by 15 Ω gives 8 A.

Question 2Electrical Theory and Principles

Resistors of 10 Ω, 20 Ω and 30 Ω are connected in series. What is the total resistance of the circuit?

  1. 600 Ω
  2. 60 Ω Correct answer.
  3. 20 Ω
  4. 6.7 Ω

Explanation

In a series circuit the total resistance is the sum of the individual resistances. Adding 10 Ω, 20 Ω and 30 Ω gives 60 Ω.

Question 3Electrical Theory and Principles

A current of 2 A flows through a 25 Ω resistor. At what rate is power dissipated in the resistor?

  1. 100 W Correct answer.
  2. 50 W
  3. 12.5 W
  4. 200 W

Explanation

Resistive power can be found with P = I²R. Squaring 2 A gives 4, and multiplying by 25 Ω gives 100 W.

Question 4Electrical Theory and Principles

Two 60 Ω resistors are connected in parallel. What is the equivalent resistance of the combination?

  1. 60 Ω
  2. 15 Ω
  3. 30 Ω Correct answer.
  4. 120 Ω

Explanation

For two equal resistors in parallel, the equivalent resistance is half of one resistor's value. Half of 60 Ω is 30 Ω.

Question 5Electrical Theory and Principles

The ampere is defined as which of the following?

  1. One joule of energy per coulomb of charge
  2. One volt per coulomb of charge
  3. One ohm of resistance per volt
  4. One coulomb of charge passing a point per second Correct answer.

Explanation

Current is the rate of charge flow, so one ampere equals one coulomb per second. The coulomb-per-second relationship is the fundamental definition of the ampere.

Question 6Electrical Theory and Principles

An alternating waveform has a frequency of 60 Hz. What is the duration of one complete cycle?

  1. 0.6 s
  2. 6 ms
  3. 60 s
  4. 16.7 ms Correct answer.

Explanation

Period is the reciprocal of frequency, so T = 1/f. One divided by 60 Hz equals about 0.0167 s, or 16.7 ms.

Question 7Electrical Theory and Principles

According to Kirchhoff's current law, the total current entering a junction at any instant must equal which quantity?

  1. The product of the currents in the outgoing branches
  2. The voltage at the junction divided by the total resistance
  3. The sum of the resistances connected at the junction
  4. The total current leaving the junction Correct answer.

Explanation

Kirchhoff's current law expresses conservation of charge at a node. Whatever current flows in must flow out, so the entering and leaving currents are equal at every instant.

Question 8Electrical Theory and Principles

What happens to the capacitive reactance of a capacitor as the frequency of the applied voltage increases?

  1. It increases in direct proportion to frequency
  2. It decreases Correct answer.
  3. It rises briefly and then falls to zero
  4. It remains unchanged

Explanation

Capacitive reactance is given by XC = 1/(2πfC), so frequency appears in the denominator. As frequency rises, the reactance falls.

Question 9Electrical Theory and Principles

Power factor is the ratio of which two quantities?

  1. Reactive power to true power
  2. True power to apparent power Correct answer.
  3. Voltage to current
  4. Apparent power to true power

Explanation

Power factor equals real (true) power divided by apparent power, and for a sinusoidal circuit it equals the cosine of the phase angle. It indicates how much of the apparent power does useful work.

Question 10Electrical Theory and Principles

What is the inductive reactance of a 0.1 H inductor connected to a 60 Hz source? Use π ≈ 3.14.

  1. 37.7 Ω Correct answer.
  2. 377 Ω
  3. 0.10 Ω
  4. 6.0 Ω

Explanation

Inductive reactance is calculated as XL = 2πfL. Substituting gives 2 × 3.14 × 60 × 0.1, which equals about 37.7 Ω.

Question 11Electrical Theory and Principles

A 30 Ω resistor is connected in series with a coil having an inductive reactance of 40 Ω. What is the impedance of the series combination?

  1. 1200 Ω
  2. 70 Ω
  3. 50 Ω Correct answer.
  4. 10 Ω

Explanation

Resistance and reactance combine vectorially, so Z = √(R² + XL²). That is √(900 + 1600) = √2500 = 50 Ω.

Question 12Electrical Theory and Principles

For a balanced three-phase load, total real power is calculated as which expression?

  1. √3 × VL × IL ÷ PF
  2. VL × IL × PF
  3. 3 × VL × IL
  4. √3 × VL × IL × PF Correct answer.

Explanation

Three-phase real power equals the square root of three times line voltage times line current times power factor. The √3 factor accounts for the relationship between line and phase quantities.

Question 13Electrical Theory and Principles

An ideal transformer with a 4:1 turns ratio has 480 V applied to its primary, and its secondary supplies 12 A. What current flows in the primary?

  1. 3 A Correct answer.
  2. 0.75 A
  3. 48 A
  4. 12 A

Explanation

In an ideal transformer, primary volt-amperes equal secondary volt-amperes, so the currents are in inverse ratio to the voltages. A step-down ratio of 4:1 means the primary current is one quarter of the secondary current, or 3 A.

Question 14Electrical Theory and Principles

A conductor has a fixed cross-sectional area and temperature. If its length is doubled, its resistance will be which of the following?

  1. Quadrupled
  2. Unchanged
  3. Doubled Correct answer.
  4. Halved

Explanation

Resistance is directly proportional to length by the relation R = ρL/A. Doubling length while area stays constant doubles the resistance.

Question 15Electrical Theory and Principles

A sine wave has a peak value of 170 V. What is its RMS value?

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

Explanation

For a sine wave, RMS value equals peak value divided by the square root of two. Dividing 170 V by 1.414 gives approximately 120 V.

Question 16Electrical Theory and Principles

A 40 Ω resistor and a 60 Ω resistor are connected in series across a 100 V supply. What is the voltage across the 60 Ω resistor?

  1. 60 V Correct answer.
  2. 20 V
  3. 40 V
  4. 100 V

Explanation

The same current flows through both resistors, so voltage divides in proportion to resistance. The 60 Ω resistor takes 60/100 of the 100 V total, which is 60 V.

Question 17Electrical Theory and Principles

In a series RLC circuit at resonance, which condition applies?

  1. Resistance falls to zero at resonance
  2. Line current drops to zero at resonance
  3. Impedance reaches its maximum value
  4. Z equals R and XL equals XC Correct answer.

Explanation

At resonance the inductive and capacitive reactances are equal in magnitude, so they cancel and leave only resistance in the impedance. Impedance is therefore at a minimum and current is at a maximum.

Question 18Electrical Theory and Principles

A 100 µF capacitor is charged to a potential difference of 200 V. How much energy is stored in the electric field?

  1. 20 J
  2. 0.02 J
  3. 2 J Correct answer.
  4. 4 J

Explanation

Energy stored in a capacitor is E = ½CV². With C = 100 × 10⁻⁶ F and V = 200 V, the energy is 0.5 × 100 × 10⁻⁶ × 40,000 = 2 J.

Question 19Electrical Theory and Principles

A 120 V source feeds two parallel branches: one is a 20 Ω resistor and the other is a capacitor with 20 Ω of reactance. What is the total line current?

  1. 6 A
  2. 8.49 A Correct answer.
  3. 12 A
  4. 17 A

Explanation

Each branch draws 120 V ÷ 20 Ω = 6 A, but the resistive and capacitive currents are 90 degrees out of phase. They add vectorially as √(6² + 6²), giving about 8.49 A.

Question 20Electrical Theory and Principles

In a balanced delta-connected load, how does the line current relate to the phase current?

  1. Line current is one third of phase current
  2. Line current is √3 times phase current Correct answer.
  3. Line current is three times phase current
  4. Line current equals phase current

Explanation

In a delta connection the line conductors supply the vector sum of two phase currents that are 60 degrees apart, giving a factor of the square root of three. Line current is therefore √3 times the phase current, while line and phase voltages are equal.

Question 21General Electrical Knowledge and Work Practices / Safety

Under lockout/tagout practice, who is permitted to remove a personal lock and tag from an isolation point?

  1. Any other qualified electrician on the same shift
  2. The person who applied the lock and tag Correct answer.
  3. The maintenance planner responsible for the area
  4. The site security supervisor on duty

Explanation

A personal lock and tag belong to the individual who fitted them, because only that person knows the work is finished and the equipment is safe to re-energise. Removal by anyone else requires a documented exception procedure with supervision.

Question 22General Electrical Knowledge and Work Practices / Safety

A 30 mA residual current device (RCD) protecting a hand-held tool operates when the earth leakage current reaches which value?

  1. About 3 mA
  2. About 30 A
  3. About 300 mA
  4. About 30 mA Correct answer.

Explanation

The figure in an RCD designation is its rated residual operating current, so a 30 mA device trips at roughly 30 mA of live-to-neutral imbalance within the time limits of the product standard. This level is chosen because it is below the current that normally causes ventricular fibrillation.

Question 23General Electrical Knowledge and Work Practices / Safety

Which extinguishing medium is appropriate for a small fire in an energised electrical panel?

  1. Aqueous film-forming foam applied as a spray
  2. Carbon dioxide from a hand extinguisher Correct answer.
  3. Wet chemical sprayed from a cartridge unit
  4. Pressurised water delivered from a hose reel

Explanation

Carbon dioxide does not conduct electricity and leaves no residue, so it can be applied to live equipment without creating a shock path or damaging the panel. Water, foam and wet chemicals are conductive and can spread the fire and electrify the operator.

Question 24General Electrical Knowledge and Work Practices / Safety

What is the main purpose of the protective earth (ground) conductor in a Class I appliance?

  1. It balances load current across the three supply phases
  2. It carries the operating current back to the supply transformer
  3. It limits the level of voltage ripple appearing on the appliance supply
  4. It provides a low-impedance path so the protective device trips Correct answer.

Explanation

The protective conductor carries no current in normal service; during an earth fault it gives a low-impedance return path so the fuse or breaker operates quickly and the touch voltage on the metal enclosure stays low.

Question 25General Electrical Knowledge and Work Practices / Safety

An electrician finds a colleague collapsed and still in contact with a live conductor. What is the first action?

  1. Pour water on the conductor to cool it down
  2. Start chest compressions where the casualty lies
  3. Pull the casualty clear by the arm immediately
  4. Isolate the supply before touching the casualty Correct answer.

Explanation

Touching a casualty who is still in contact with a live conductor makes the rescuer a second victim. The supply must be isolated first, or the casualty removed with an insulated device by a trained person, before first aid begins.

Question 26General Electrical Knowledge and Work Practices / Safety

Which procedure correctly proves a circuit is dead before work begins?

  1. Confirm the circuit breaker handle is locked in the open position
  2. Prove the tester live, test the circuit, then re-prove the tester Correct answer.
  3. Test the circuit with the tester and rely on a single reading obtained
  4. Ask the plant operator to confirm the circuit has been switched off

Explanation

The voltage indicator is checked against a known live source or proving unit before and after the test, so a tester that fails during use cannot give a false 'dead' reading. Absence of voltage must be proved on every conductor at the point of work.

Question 27General Electrical Knowledge and Work Practices / Safety

Before working on a capacitor bank that has been isolated, what must be done?

  1. Nothing, because the isolator has already removed all the stored energy
  2. Measure the capacitance with a multimeter set to the ohms range
  3. Discharge it through a resistor and confirm zero volts Correct answer.
  4. Short the terminals together with an insulated screwdriver

Explanation

Capacitors can retain a lethal charge long after isolation, so they must be discharged through a suitable resistor or discharge unit and the voltage then proved at zero. Direct shorting with a hand tool can produce a violent arc and damage the terminals.

Question 28General Electrical Knowledge and Work Practices / Safety

What is the maximum working voltage (AC) for which Class 0 rubber insulating gloves are rated?

  1. 17 000 V
  2. 500 V
  3. 1 000 V Correct answer.
  4. 750 V

Explanation

Rubber insulating gloves are graded by maximum use voltage: Class 00 covers 500 V, Class 0 covers 1 000 V, Class 1 covers 7 500 V and Class 2 covers 17 000 V. The class marking must be checked, along with a valid air test and periodic retest.

Question 29General Electrical Knowledge and Work Practices / Safety

When is live working on electrical equipment normally justified?

  1. When de-energising would create a hazard greater than live work Correct answer.
  2. When the production schedule does not permit a planned shutdown
  3. When the electrician holds a current first-aid and CPR certificate
  4. When the circuit is rated at less than 1 000 V

Explanation

Live work is allowed only where de-energising introduces a greater hazard (for example, shutting down ventilation or life-support equipment) or is genuinely infeasible, and then only under a permit, risk assessment and suitable PPE. Production convenience is never a justification.

Question 30General Electrical Knowledge and Work Practices / Safety

Which instrument is used to measure the insulation resistance of a motor winding?

  1. A clamp meter set to the 400 A AC current range
  2. An insulation tester applied between the winding and earth Correct answer.
  3. A digital multimeter set to the continuity buzzer range and probes
  4. A three-electrode earth resistance tester with spikes

Explanation

An insulation tester applies a DC test voltage such as 500 V or 1 000 V between the winding and earth and displays the resulting resistance in megohms. A multimeter's low test voltage cannot assess insulation quality.

Question 31General Electrical Knowledge and Work Practices / Safety

Which value of 50/60 Hz current flowing through the human body is most likely to cause ventricular fibrillation?

  1. 50 mA Correct answer.
  2. 0.5 mA
  3. 5 A
  4. 5 mA

Explanation

The let-go threshold is around 10 mA, and currents of roughly 30 mA to 100 mA passing through the chest for a fraction of a second can trigger ventricular fibrillation. Higher currents cause burns and cardiac arrest, while currents of a few milliamps are only perceptible.

Question 32General Electrical Knowledge and Work Practices / Safety

What is the function of arc-rated clothing worn while switching energised equipment?

  1. It conducts static charge safely to earth
  2. It prevents the wearer from receiving any electric shock
  3. It limits burn injury from the heat of an arc flash Correct answer.
  4. It insulates the wearer from step and touch potentials

Explanation

Arc-rated garments are designed not to ignite and to limit the burn injury caused by the radiant heat and molten metal of an arc flash. They provide no protection against electric shock, which is addressed by distance, insulation and isolation.

Question 33General Electrical Knowledge and Work Practices / Safety

A multimeter is to be used for voltage measurements on the supply side of a 415 V distribution board. Which rating is the minimum acceptable?

  1. CAT II 300 V
  2. CAT II 600 V
  3. CAT III 600 V Correct answer.
  4. CAT I 1 000 V

Explanation

The measurement category states the transient overvoltage environment the meter can withstand, and a distribution board feeder is a CAT III location. A CAT III meter of at least 600 V is therefore required; a higher voltage number does not compensate for a lower category.

Question 34General Electrical Knowledge and Work Practices / Safety

Which statement defines the arc flash boundary?

  1. The distance a person must keep from live parts to avoid shock
  2. The distance over which the sound of the arc exceeds 85 dB
  3. The distance at which incident energy is 1.2 cal/cm² Correct answer.
  4. The distance at which an arc can no longer be initiated by a person

Explanation

The arc flash boundary is the distance from the arc source at which the incident energy falls to 1.2 cal/cm² (about 5 J/cm²), the level at which a second-degree burn is possible. Inside that boundary, arc-rated PPE is required.

Question 35General Electrical Knowledge and Work Practices / Safety

A single-phase 230 V heater is rated at 2 000 W. What current does it draw in normal operation?

  1. About 8.7 A Correct answer.
  2. About 4.6 A
  3. About 17 A
  4. About 0.9 A

Explanation

For a resistive single-phase load, current equals power divided by voltage: 2 000 divided by 230 gives approximately 8.7 A. That value is then used to select the protective device and conductor size.

Question 36General Electrical Knowledge and Work Practices / Safety

Why are leather protector gloves worn over rubber insulating gloves?

  1. To provide a second layer of electrical insulation
  2. To protect the rubber glove from cuts and abrasion Correct answer.
  3. To increase the dielectric strength of the rubber glove
  4. To keep the rubber glove warm in cold weather

Explanation

Leather protectors shield the rubber glove from mechanical damage such as cuts, abrasion and punctures, which would destroy its insulating properties. They add no useful electrical insulation and must never be worn alone as insulating gloves.

Question 37Services, Feeders, and Branch Circuits

Which set of conductors is a branch circuit?

  1. The conductors between the meter and the service disconnect
  2. The conductors between the service equipment and a panelboard
  3. The conductors between the final overcurrent device and the outlets served Correct answer.
  4. The overhead conductors from the utility pole to the service point

Explanation

A branch circuit is the circuit conductors between the final overcurrent device protecting the circuit and the outlet or outlets. It does not include service conductors or feeders.

Question 38Services, Feeders, and Branch Circuits

Which set of conductors is a feeder?

  1. Conductors from the service equipment to the final branch-circuit overcurrent device Correct answer.
  2. Conductors connecting a grounding electrode to the service neutral
  3. Conductors from the final overcurrent device to a receptacle
  4. Conductors from the utility transformer to the service point

Explanation

A feeder supplies a panelboard or branch circuits and runs between the service equipment or source and the final branch-circuit overcurrent device. It carries the total load of the circuits it supplies.

Question 39Services, Feeders, and Branch Circuits

Overhead service conductors that run from the utility pole to the service point are called ___.

  1. service-entrance conductors
  2. feeder conductors
  3. service drop Correct answer.
  4. service lateral

Explanation

Overhead service conductors from the utility supply to the service point are service-drop conductors. Underground service conductors in that same role are service laterals.

Question 40Services, Feeders, and Branch Circuits

Which dwelling-unit receptacle outlet must be ground-fault circuit-interrupter protected?

  1. Bathroom Correct answer.
  2. Bedroom
  3. Living room
  4. Dining room

Explanation

Bathroom receptacle outlets in dwelling units require ground-fault circuit-interrupter protection. Bedrooms and living areas generally require arc-fault protection instead.

Question 41Services, Feeders, and Branch Circuits

The small-appliance branch circuits in a dwelling unit must have a minimum rating of ___.

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

Explanation

Dwelling-unit small-appliance branch circuits must be rated at least 20 amperes. At least two such circuits are required for kitchen and related receptacles.

Question 42Services, Feeders, and Branch Circuits

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

  1. readily accessible and nearest the point of service entrance Correct answer.
  2. only in a basement
  3. within 50 feet of the farthest receptacle
  4. inside the utility transformer vault

Explanation

The service disconnecting means must be readily accessible and located nearest the point where service conductors enter the building. This allows the service to be quickly disconnected.

Question 43Services, Feeders, and Branch Circuits

What is the minimum working-space depth required in front of service equipment?

  1. 48 inches
  2. 18 inches
  3. 24 inches
  4. 36 inches Correct answer.

Explanation

The minimum working-space depth in front of service equipment is 36 inches. This clearance provides safe access for operation and maintenance.

Question 44Services, Feeders, and Branch Circuits

In a dwelling unit, a laundry branch circuit must be rated at least ___ and may supply ___.

  1. 15 A; all general-purpose receptacles
  2. 20 A; kitchen counter receptacles
  3. 20 A; only laundry receptacle outlets Correct answer.
  4. 30 A; the laundry and bathroom receptacles

Explanation

A laundry branch circuit in a dwelling must be rated at least 20 amperes and may supply only laundry receptacle outlets. It must not be used for other general-purpose outlets.

Question 45Services, Feeders, and Branch Circuits

Along a dwelling-unit wall, the maximum distance between receptacle outlets is ___.

  1. 8 feet
  2. 24 feet
  3. 12 feet Correct answer.
  4. 6 feet

Explanation

Receptacles must be placed so that no point along the wall line is more than 6 feet from a receptacle. This results in a maximum spacing of 12 feet between outlets.

Question 46Services, Feeders, and Branch Circuits

The recommended maximum voltage drop for a branch circuit is ___.

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

Explanation

The recommended maximum voltage drop for a branch circuit is 3 percent. The recommended total drop for feeder plus branch circuit is 5 percent.

Question 47Services, Feeders, and Branch Circuits

What is the ampacity of a 12 AWG copper conductor with 60°C insulation?

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

Explanation

A 12 AWG copper conductor with 60°C insulation has an ampacity of 20 amperes. Higher-temperature insulation can allow a greater ampacity, subject to terminations and conditions of use.

Question 48Services, Feeders, and Branch Circuits

For a 2,000-square-foot dwelling, the general lighting load is ___ before demand factors.

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

Explanation

Dwelling general lighting load is calculated at 3 VA per square foot. For 2,000 square feet, the load is 2,000 × 3 = 6,000 VA before demand factors.

Question 49Services, Feeders, and Branch Circuits

Using the standard dwelling demand factors, what demand load applies to 10,000 VA of general lighting?

  1. 10,000 VA
  2. 7,000 VA
  3. 3,000 VA
  4. 5,450 VA Correct answer.

Explanation

The first 3,000 VA is taken at 100 percent and the remaining 7,000 VA at 35 percent. The demand load is 3,000 + (0.35 × 7,000) = 5,450 VA.

Question 50Services, Feeders, and Branch Circuits

A multiwire branch circuit in a dwelling unit must have ___.

  1. a means to simultaneously disconnect all ungrounded conductors Correct answer.
  2. no overcurrent protection on the neutral
  3. a separate neutral for each ungrounded conductor
  4. conductors limited to 15 AWG

Explanation

A multiwire branch circuit must have a means to simultaneously disconnect all ungrounded conductors at the panelboard. This is typically provided by handle ties or a multipole breaker.