Electrical Engineer practice questions with answers

Updated 17 September 2026 · 2 min read

These questions favour electrical principles, with electronics and maintenance practice alongside, which is the balance an engineer's written test tends to take. Work each calculation fully rather than estimating, and for design questions write down the constraints in the stem before you choose. That habit is the difference between an engineer who can defend a decision and one who guessed correctly.

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

When wiring a dual-voltage (230/460V) 9-lead 3-phase motor for high voltage (460V), how should the windings be connected?
1. In parallel
2. In a delta-only configuration
3. In a star-only configuration
4. In series
Show the answer
D. In series
For a dual-voltage motor, the windings are connected in series for the high-voltage application so that each winding receives its rated voltage.
Original practice question, written against published exam objectives. Open this question
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
An electrician installs a 100A subpanel in a detached garage using a 3-wire feeder (two hots, one neutral) and bonds the neutral to the ground bus at the subpanel. What is the primary safety risk here?
1. The subpanel will not have 240V available
2. Objectionable current will flow on the neutral and metal enclosures back to the main panel
3. The breakers in the subpanel will trip instantly
4. The ground rod at the garage will overheat
Show the answer
B. Objectionable current will flow on the neutral and metal enclosures back to the main panel
NEC requires a 4-wire feeder (separated neutral and ground) to detached buildings to prevent the neutral current from traveling on the equipment grounding path.
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
A homeowner complains that a newly installed bedroom outlet trips the breaker whenever a lamp is turned on. The panel has a dual-function AFCI/GFCI breaker. What is the most likely cause?
1. A shared neutral or ground fault is triggering the AFCI/GFCI protection
2. The breaker is sized too small for a bedroom
3. The receptacle is installed upside down
4. The lamp is drawing more than 20 amps
Show the answer
A. A shared neutral or ground fault is triggering the AFCI/GFCI protection
Dual-function breakers are sensitive to arc faults and ground faults. A shared neutral or slight ground leakage will cause them to trip immediately upon load.
Original practice question, written against published exam objectives. Open this question
A supervisor tests your knowledge of bipolar junction transistor. Which answer is best?
1. uses base current to control a larger collector-emitter current
2. cannot operate as a switch
3. is controlled only by light
4. has only two terminals
Show the answer
A. uses base current to control a larger collector-emitter current
bipolar junction transistor uses base current to control a larger collector-emitter current.
Original practice question, written against published exam objectives. Open this question
A technician is documenting ladder-logic contact. Which statement belongs in the notes?
1. replaces the PLC processor
2. is always an analog output
3. tests a logical condition associated with an input or internal bit
4. physically carries motor current in every case
Show the answer
C. tests a logical condition associated with an input or internal bit
ladder-logic contact tests a logical condition associated with an input or internal bit.
Original practice question, written against published exam objectives. Open this question
A technician repairing a failed boiler feed pump decides to analyze why the seal failed. They discover the baseplate is vibrating due to improper grouting, so they regrout the baseplate to prevent future seal failures. What strategy does this represent?
1. Proactive/Reliability-Centered Maintenance
2. Corrective Maintenance
3. Reactive Maintenance
4. Preventive Maintenance
Show the answer
A. Proactive/Reliability-Centered Maintenance
Proactive maintenance goes beyond fixing the immediate breakdown (reactive) and addresses the root cause of the failure to eliminate the defect entirely.
Original practice question, written against published exam objectives. Open this question

Treat every calculation as a design decision

Behind each number is something physical: a cable that will or will not overheat, a breaker that will or will not clear a fault. When you check an answer, ask what it would mean on site. A cable calculation that gives a smaller size than intuition suggests deserves a second look at the derating factors.

Where engineers lose marks

Most wrong answers on these questions come from four places: mixing line and phase values, confusing kW and kVA, ignoring a derating condition, and answering the question the candidate expected rather than the one asked. Note which of the four catches you most often, because it will catch you again under time pressure.

After this set

The worked calculations further down were generated for this page and independently recomputed before publication. Use them to time yourself. More electrical questions from the full bank follow them.

Two calculations to try

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

Real power in a balanced three-phase load
A balanced three-phase motor is supplied at 400 V line-to-line, draws 80 A line current, and runs at a power factor of 0.95. What real power does it take?
Show the working
1. For a balanced three-phase load: P = √3 × VL × IL × power factor.
2. P = 1.732 × 400 × 80 × 0.95
3. P = 52654 W = 52.65 kW
Answer: 52.65 kW
Voltage drop on a single-phase copper run
A single-phase 230 V circuit uses a 35 m run of 6 mm² copper cable carrying 32 A. Taking the resistivity of copper as 0.0172 Ω·mm²/m, what is the voltage drop, and what percentage of 230 V is it?
Show the working
1. Current flows out and back, so the conductor length is doubled: Vd = (2 × L × I × ρ) ÷ A.
2. Vd = (2 × 35 × 32 × 0.0172) ÷ 6
3. Vd = 6.42 V
4. As a share of supply: 6.42 ÷ 230 × 100 = 2.79 %
Answer: 6.42 V (2.79 % of 230 V)

Common questions

Why do maintenance questions appear in an engineering test?

Engineers specify equipment that other people must maintain, and many engineering posts include responsibility for existing installations. Maintainability is part of good design.

Should I memorise cable tables?

No. Understand what the tables do and which factors change a rating. Tests that need specific values normally provide them. What you must know is which factor applies in which condition, because that is the judgement a table cannot supply.