Electrical Engineer Interview Questions and How to Answer Them

Electrical engineering interviews tend to swing between two extremes. One minute you are asked to explain power factor to a non-engineer; the next you are asked how you would prove a circuit dead before letting a technician work on it. Both questions test the same thing: whether your knowledge is safe to rely on.

Below are the questions you are likely to meet, sorted by type, with notes on what a strong answer contains. Answers marked illustrative are examples only. Adjust them to your discipline (power, building services, controls, electronics, renewables) and to the codes and standards used where you work.

Quick-fire technical questions

These usually come early, to check fundamentals. Short, precise answers work best.

A calculation you may be asked to do at the whiteboard

Many panels ask for a quick calculation to see how you think. Talk through your assumptions as you go.

Illustrative question: “A three-phase motor draws 50 A at 400 V line-to-line with a power factor of 0.85. What is its real power input?”

P = √3 × V(line) × I(line) × pf
P = 1.732 × 400 × 50 × 0.85
P ≈ 29,400 W ≈ 29.4 kW

Then add the engineering judgement the panel is listening for: this is input power, not shaft output; efficiency would reduce output; and the 50 A figure drives cable sizing, protection rating and voltage drop checks. A follow-up is likely: “What would you do to reduce the current?” Good answers include power factor correction and checking the motor is not oversized for its duty.

Design questions

“Walk me through how you would size a cable for a new circuit.”

Interviewers want a method, not a single number. Cover design current, protective device rating, installation method and correction factors (grouping, ambient temperature, thermal insulation), voltage drop, fault level and disconnection time, and the standard you work to. Mention that you check the result against the software output rather than trusting the software alone.

“How would you approach the electrical design for a new building?”

Start with loads and diversity, then supply arrangement, main distribution, sub-distribution, life-safety systems, standby power, metering and future expansion. Show you would coordinate early with mechanical, structural and architectural teams on plant space, riser sizes and routes.

“Tell me about a design decision you had to defend.”

This is a technical behavioural question. Pick a real example: a transformer size, a choice between ring and radial distribution, a UPS topology. Explain the options, the criteria, the trade-off you chose and how you persuaded the client or the senior engineer.

Safety questions

Expect at least one, whatever the role. In Great Britain, the Electricity at Work Regulations 1989 give a clear structure that many panels use even abroad:

• Regulation 12 requires suitable means for cutting off the supply and isolating equipment, and defines isolation as disconnection and separation from every source of electrical energy, in a secure way.
• Regulation 13 requires adequate precautions to stop equipment that has been made dead from becoming live again while work is carried out.
• Regulation 14 prohibits work on or near live conductors unless it is unreasonable to make them dead, it is reasonable to work live, and suitable precautions are taken to prevent injury.
• Regulation 16 says no one should do work needing technical knowledge or experience to prevent danger unless they have it or are suitably supervised.

“How would you make a circuit safe to work on?”

Illustrative answer: “Identify the circuit from up-to-date drawings, isolate at the correct point, secure the isolation with a lock and tag, then prove dead with an approved voltage indicator that I have proved on a known source before and after the test. Only then would I issue a permit, if the site uses one. If a conductor cannot be made dead, I would stop and escalate, because live work needs a justification and specific precautions.”

“A site manager asks you to approve live working to save a shutdown. What do you say?”

The panel is testing whether you will hold the line. Explain that the commercial cost of a shutdown is not, on its own, a reason to work live, and offer alternatives: planned out-of-hours shutdown, temporary supply, or splitting the work. Show that you would document the decision either way.

Commissioning and fault-finding questions

“Describe a fault you diagnosed.”

Use a clear sequence: symptom, information gathered, hypotheses, tests that ruled each one in or out, root cause, fix, and what you changed to stop it happening again. Interviewers like candidates who mention reading drawings and logs before reaching for a meter.

“What tests would you expect before energising a new installation?”

Cover visual inspection, continuity of protective conductors, insulation resistance, polarity, earth fault loop impedance or equivalent, RCD operation and functional testing, in line with the standard used locally. Then documentation: test certificates and as-built drawings.

“A motor trips on start-up every morning. Where do you start?”

Good answers check the obvious first: protection settings against motor data, starting method, supply voltage at start, mechanical load and ambient conditions. Then look at insulation resistance and the motor itself.

Questions by specialism

• Power systems: How would you carry out a short-circuit study? What is the difference between a distance relay and an overcurrent relay? How do you manage reactive power on a network?
• Building services: How do you design emergency lighting and fire alarm interfaces? How do you coordinate with BMS? How would you size a standby generator?
• Controls and automation: Explain a PID loop and how you tune it. How do you approach a PLC program change on a live plant? What is a safety instrumented function?
• Renewables: How do string inverters differ from central inverters? How do you protect a PV array? What grid-connection studies are usually needed?
• Electronics: How do you reduce EMI on a board? How do you choose between a linear and a switching regulator?

Professional development questions

Panels often ask about chartership or licensure, especially for mid-level roles.

• In the UK, the Engineering Council’s UK-SPEC assesses five areas of competence and commitment, running from knowledge and understanding to professional commitment. Having one electrical example for each makes a good interview bank.
• In the US, NCEES offers three PE Electrical and Computer exams: Power, Electronics/Controls/Communications, and Computer Engineering. As of November 2026, all are computer-based; the Power exam has 80 questions and 8 hours of exam time within a 9-hour appointment, and NCEES provides an electronic reference handbook during the exam.

If you are on a route to registration, say where you are and what evidence you are building. If not, explain how you keep up with code changes and new technology.

Behavioural questions with an electrical slant

• Tell me about a time you found an error in someone else’s design.
• Describe a time you had to explain a technical risk to a non-technical client.
• Tell me about a commissioning deadline you could not meet. What did you do?
• Describe a time you stopped work for safety reasons.

Keep each answer to about two minutes. State your own actions, not the team’s.

Questions to ask in an electrical engineer interview

1. What is the split between design, site and commissioning work in this role?
2. Which standards and design software does the team use?
3. How are design checks and sign-offs handled?
4. Does the company support professional registration, and how?
5. What projects would I join first?

Before the interview

Pick three projects you can talk about in depth, revise the fundamentals in the table above, and practise one calculation aloud. Make sure your CV shows the same projects with the voltages, systems and standards involved. The electrical engineer resume builder has sections for projects and technical skills, and the resume questions hub answers common CV queries.

Frequently asked questions

What technical questions are asked in an electrical engineer interview?

Common ones cover power factor, protection devices, earthing, star and delta connections, harmonics, transformers, discrimination, cable sizing and safe isolation. Panels often add a short calculation.

How do I answer electrical engineer interview questions about safety?

Describe a clear isolation sequence: identify, isolate, lock and tag, prove dead with a tested instrument, and use a permit where required. Show you would refuse unjustified live work and escalate.

Should I mention chartership or PE licensure?

Yes, if you are working towards it. Explain your current stage and the evidence you are building. Interviewers see it as a sign of professional commitment.

What are good questions to ask in an electrical engineer interview?

Ask about the balance of design and site work, the standards and software used, how designs are checked, support for professional registration and the first projects you would join.

How should a fresh graduate prepare for an electrical engineer interview?

Revise fundamentals, prepare to talk about your final-year project in technical detail, practise a basic three-phase calculation and have one example of teamwork and one of solving a problem.

Sources

• The Electricity at Work Regulations 1989, Part II, legislation.gov.uk (UK National Archives)
• UK-SPEC: Professional engineering competence and commitment, Engineering Council
• PE Electrical and Computer exams, NCEES