Electrician practice questions with answers

Updated 16 September 2026 · 2 min read

These practice questions concentrate on electrical principles and installation, with maintenance practice alongside, because that is where an electrician's knowledge is tested hardest. Treat every question about working on a circuit as if you were standing at the distribution board. Choose your answer, say why it is safe, then open the explanation.

How this guide was made

Written for this site with AI assistance, then checked automatically before publishing. The topic table, sample questions, worked examples and study plan are generated from this site’s question bank: each worked example is recalculated by separate code, and each sample answer says where it came from.

The guide deliberately states no salaries, grades, pass marks or exam dates. Those change, and they could not be checked here, so take them from the advert itself.

This site is independent and is not affiliated with MIFOTRA or any employer.

Practice questions

You are replacing a 10 HP, 460V, 3-phase motor. The nameplate lists the Full Load Amps (FLA) as 14.0A and the Service Factor as 1.15. What is the maximum setting for the overload relays according to general NEC rules?
1. 19.6A (140% of FLA)
2. 17.5A (125% of FLA)
3. 14.0A (100% of FLA)
4. 16.1A (115% of FLA)
Show the answer
B. 17.5A (125% of FLA)
For motors with a Service Factor of 1.15 or greater, the NEC allows the overload device to be sized up to 125% of the nameplate FLA (14.0 * 1.25 = 17.5A).
Original practice question, written against published exam objectives. Open this question
While remodeling a residential bathroom, an apprentice wires a new 20A receptacle directly to the vanity light switch circuit without GFCI protection. What specific code violation has occurred?
1. The receptacle needs AFCI, not GFCI protection
2. Bathroom receptacles must have GFCI protection and be on a dedicated 20A circuit
3. Lights and receptacles must share a 15A AFCI circuit
4. The receptacle must be on a 15A circuit
Show the answer
B. Bathroom receptacles must have GFCI protection and be on a dedicated 20A circuit
NEC requires bathroom receptacles to be GFCI protected and supplied by a dedicated 20A branch circuit that does not serve other areas.
Original practice question, written against published exam objectives. Open this question
A large induction motor utilizes a star-delta starter to reduce inrush current. During the start sequence, the motor starts in star but trips the main breaker the exact moment it transitions to delta. What is the most likely cause?
1. The motor requires a soft starter instead of star-delta
2. The timer is set too long, overheating the star contactor
3. The phase sequencing in the delta contactor is reversed, causing a dead short or massive torque spike
4. The thermal overloads are set too low
Show the answer
C. The phase sequencing in the delta contactor is reversed, causing a dead short or massive torque spike
If the wiring on the delta contactor is not phased correctly matching the motor rotation, the transition creates a massive phase-to-phase short or instant torque reversal, tripping the breaker immediately.
Original practice question, written against published exam objectives. Open this question
A maintenance tech uses a megohmmeter to test a 480V 3-phase pump motor. The reading from phase A to ground is 0.5 MΩ. What should the tech conclude?
1. The reading is acceptable if the motor is warm
2. The motor is in perfect condition and ready to run
3. The motor insulation is severely degraded and the motor should be removed from service
4. The tech should use a multimeter instead of a megohmmeter
Show the answer
C. The motor insulation is severely degraded and the motor should be removed from service
For a 480V motor, insulation resistance should generally be >1 MΩ. A 0.5 MΩ reading indicates significant insulation breakdown or moisture ingress.
Original practice question, written against published exam objectives. Open this question
An industrial oven keeps tripping its breaker intermittently. A tech checks the amp draw and finds it steady at 38A on a 40A breaker. Why is the breaker tripping?
1. The continuous load exceeds 80% of the breaker rating
2. The oven has a severe ground fault
3. The voltage is fluctuating too much
4. The breaker is defective and must be replaced
Show the answer
A. The continuous load exceeds 80% of the breaker rating
Standard breakers are rated to carry 80% of their rating continuously. 80% of 40A is 32A. A 38A continuous load will cause the thermal element to trip eventually.
Original practice question, written against published exam objectives. Open this question
When conducting an outdoor thermography inspection of a substation on a bright sunny day, the technician notes that all the ceramic insulators on the east side appear extremely hot. What must the technician consider?
1. Ceramic inherently generates heat on the east side due to magnetic fields
2. The east side of a substation always carries more current
3. The emissivity of ceramic changes depending on the time of day
4. Solar loading (sunlight) is heating the components, masking or mimicking electrical faults
Show the answer
D. Solar loading (sunlight) is heating the components, masking or mimicking electrical faults
Solar loading is a major factor in outdoor thermography. Sun shining on equipment heats it up, which can create false hotspots or hide true electrical faults.
Original practice question, written against published exam objectives. Open this question
A maintenance electrician scans a 3-phase motor starter with an infrared camera. Phase A is 45°C, Phase B is 46°C, and Phase C is 95°C. What is the most likely cause of this discrepancy?
1. The infrared camera needs to be recalibrated
2. Phase C is carrying normal load current
3. A loose connection on Phase C causing high resistance heating
4. The motor has a blown Phase A fuse
Show the answer
C. A loose connection on Phase C causing high resistance heating
A single hot phase in a 3-phase connection is almost always caused by high resistance at a loose, corroded, or failing termination.
Original practice question, written against published exam objectives. Open this question
A technician is sizing the branch circuit conductors for a single 25 HP, 460V, 3-phase motor with a table FLC of 34A. What is the minimum ampacity required for these conductors?
1. 34A
2. 42.5A
3. 40A
4. 85A
Show the answer
B. 42.5A
NEC requires branch circuit conductors for a single continuous duty motor to be sized at 125% of the motor full-load current rating (FLC). 34A * 1.25 = 42.5A.
Original practice question, written against published exam objectives. Open this question

Separate the calculation from the judgement

Some questions are pure calculation, and a slip in arithmetic loses the mark. Others are about judgement, such as which device to fit or which test to do next. For calculation questions, write the formula before the numbers. For judgement questions, check whether your answer would be safe and compliant, not only whether it would work.

When you get one wrong

Note whether the mistake was a formula, a unit, a rule about protection or earthing, or a safety step you missed. Unit errors, such as mixing watts and kilowatts, are common and easy to fix once you notice the pattern. Safety misses matter most, because the same habit on site could hurt someone.

After this set

The two worked calculations below were generated for this page and checked by separate code, so use them to test your method against the clock. More electrical questions from the full bank follow them. Treat those as a second round once you are confident with the set above.

Two calculations to try

Try each one on paper first. Every figure is generated and then recalculated by separate code before it is published.

Find an unknown resistance
A component drops 25 V while carrying 2.5 A. What is its resistance?
Show the working
1. Rearrange Ohm’s law for resistance: R = V ÷ I.
2. R = 25 V ÷ 2.5 A
3. R = 10 Ω
Answer: 10 Ω
Power from voltage and current
A load connected to 24 V draws 0.5 A. How much power does it use?
Show the working
1. Power is voltage times current: P = V × I.
2. P = 24 V × 0.5 A
3. P = 12 W
Answer: 12 W

Common questions

Why do some questions cover maintenance rather than installation?

Electricians spend much of their working life maintaining existing installations. Tests include maintenance scenarios because diagnosing and repairing faults safely is core to the job.

How should I practise without a workshop?

Draw circuits, work calculations by hand, and study photos of distribution boards and protective devices. Reliable training videos of testing procedures help you picture each step.