Electrical engineer interview questions, with worked answers

How to use these questions

Practise each short answer aloud, then add a design of your own: what it had to do, the part or topology you chose, how you measured it and what you would change. Electronics interviews often put a schematic in front of you to review; automation interviews may show a PLC program or a cabinet drawing. Practise thinking aloud while you read one.

What an electrical engineer is expected to know

• Circuits: analog and digital basics, part choice with margins, and simulation in SPICE or MATLABAsked in 2% of electrical engineer ads (as of 5 Nov 2026).Simulate a control loop, a filter or a power stage, and evaluate measurements..
• Boards: schematic and layout in a tool such as Altium or KiCad, and what makes a board easy to build and test.
• Power and control: power supplies and drives, or PLCAsked in 9% of electrical engineer ads (as of 5 Nov 2026).Program, test and commission PLCs, often Siemens S7 in TIA Portal, for machines and plants. programming for machines, depending on the job.
• Firmware basics: enough C or C++Asked in 13% of electrical engineer ads (as of 5 Nov 2026).Read and write C or C++ for microcontrollers: drivers, start-up code and tests on the board. to bring up a microcontroller with the software team.
• Standards and tests: safety and EMC rules of the markets, testingAsked in 8% of electrical engineer ads (as of 5 Nov 2026).Plan and run tests of firmware and boards, from bring-up to the production test. from bring-up to production, and FMEAAsked in 4% of electrical engineer ads (as of 5 Nov 2026).Work inside the quality system: released schematics, change control, FMEA and 8D..

Circuits and PCB design

Walk me through how you design a circuit, from the requirement to the schematic.

What they check: a method that starts from requirements and worst cases, not from a favourite part.

Short answer: "I write down the requirements first: inputs and outputs, voltages and currents, accuracy, temperature range, cost and the standards that apply. Then a block diagram, part choice with margins, a calculation and a simulation of the critical parts, for example in LTspice. The schematic follows, with every part's value justified, and a review by a colleague before layout."

The full answer: Choose parts with derating, so each runs well below its limits: a capacitor at a fraction of its rated voltage, a resistor at about half its power. Check the worst case over temperature and tolerance, not only the typical value. Prefer parts with more than one source and a long life ahead. Add test points and a way to program and debug the board. Keep the schematic readable: clear blocks, net names and notes on why a value was chosen.

A weak answer: "I take the circuit from the data sheet and adjust it." Follow-up: "The board must run from minus 40 to plus 85 degrees." Check every part's rating and drift over that range, and the start-up at the cold end.

What do you watch for when you lay out a printed circuit board (PCB)?

What they check: that you know layout decides whether a good schematic works.

Short answer: "A solid ground plane with short return paths, decoupling capacitors right at the pins, and the noisy parts, such as switching power stages, kept small and away from sensitive analog parts. Track widths sized for the current, thermal paths for hot parts, and the spacing that high voltages need. And the manufacturer's design rules from the start, so the board can be built and tested."

The full answer: Plan the layer stack-up before routing; a four-layer board with inner ground and power planes solves many problems. Every signal current returns somewhere: give it a path right under the trace. Size currents with the IPC rules, international industry standards for boards. Keep the clearance and creepage distances of the safety standard where mains voltage is present. Tools differ, such as Altium in many companies, KiCad, free and growing fast, and Eagle, which its maker has retired, so many teams have moved its designs. Hold a layout review with the schematic open.

A weak answer: "The autorouter does the layout." Follow-up: "The first boards get very hot near the regulator." Measure, then add copper area and thermal vias, or choose a more efficient regulator.

Power electronics

How does a switching power supply work, and where does it usually go wrong?

What they check: the basics of power electronics and the practical problems behind them.

Short answer: "A buck converter, for example, switches a transistor on and off fast; an inductor and a capacitor smooth the pulses into a lower DC voltage, set by the share of time the switch is on. It wastes little power compared with a linear regulator. It goes wrong in the layout of the fast switching loop, in an unstable control loop, in parts too hot, and in noise that fails the EMC test."

The full answer: Losses come from the switch resistance when on and from each switching edge; a faster edge saves heat but makes more noise. Choose the inductor so it does not saturate at peak current. Check the control loop's stability with a load step and, where possible, a measurement of the loop gain. Measure ripple with a short ground spring on the probe, not the long clip. Keep the loop of switch, diode and input capacitor as small as possible on the board.

A weak answer: "I use the reference design, so it works." Follow-up: "The output rings badly after a load step." Check the compensation and the output capacitor, and measure again.

How do you size the power stage of a motor drive or an inverter?

What they check: power semiconductors, thermal design and margins.

Short answer: "From the motor and the supply: peak and continuous current, DC link voltage and switching frequency. I choose MOSFETs, IGBTs or silicon carbide parts with voltage margin for spikes, calculate conduction and switching losses, and size the heat sink so the junction stays well below its limit at the worst ambient temperature. Gate drive, dead time and protection against short circuits come next."

The full answer: Silicon carbide switches faster with lower losses, which allows smaller parts but needs more care with layout and EMC. The DC link capacitors carry high ripple current and often decide the life of the drive. Plan protection: overcurrent, overvoltage, temperature, and a safe state when something fails. Prove the thermal design with a measurement at full load and the highest ambient temperature.

A weak answer: "I pick the biggest transistor we have." Follow-up: "The drive fails after months in the field." Look at temperature cycling, capacitor ageing and voltage spikes with a long cable.

Embedded basics

What does an electrical engineer need to know about the microcontroller and its firmware?

What they check: that you can design hardware that firmware can work with, and bring it up together.

Short answer: "I choose the microcontroller with the firmware team: the peripherals we need, such as ADCs, timers and interfaces, memory, power use and the tools. On the board, a clean supply, a reset circuit and a stable clock, a debug and programming connector, and protection on every input from outside. I can write enough C or C++Asked in 13% of electrical engineer ads (as of 5 Nov 2026).Read and write C or C++ for microcontrollers: drivers, start-up code and tests on the board. to test the hardware myself."

The full answer: Document the pin use and the electrical limits in a short hardware guide for the firmware team. Add a watchdog and brown-out detection so the device recovers from faults. Plan test hooks: spare pins, a status LED, a serial port. Keep firmware and test scripts in GitAsked in 8% of electrical engineer ads (as of 5 Nov 2026).Keep firmware, scripts and sometimes design files under version control with the team. so everyone works on the same version, and test the boards with automated scripts, for example in PythonAsked in 19% of electrical engineer ads (as of 5 Nov 2026).Scripts for test benches, measurement data and small tools around the lab.. In the EU, the EU's Cyber Resilience Act brings security duties for connected products, so plan secure updates early.

A weak answer: "Firmware is the software team's job." Follow-up: "The ADC readings are noisy." Check the reference voltage, the layout of the analog input, filtering and the sampling time.

EMC

Your board fails the EMC test. What do you do?

What they check: a calm, methodical approach to the test most new products fail at least once.

Short answer: "EMC, electromagnetic compatibility, means a device does not disturb others and is not disturbed by them. First I read the report: which test failed, at which frequencies or levels. For emissions, I find the source with a near-field probe and match the frequency to a clock or a switching stage. Then the fix: filtering, layout, a ferrite on a cable, shielding, or a slower edge. I test it in a pre-compliance setup before booking the lab again."

The full answer: EMC has two halves: emissions, what the device sends out, and immunity, what it must withstand, such as electrostatic discharge, fast bursts and surges, set out in the international IEC 61000 series. In the EU, the EU EMC Directive requires both for CE marking in the EU; in the US, the US FCC rules cover emissions. Cables are often the antenna, so look at what leaves the board. Design for EMC from the start: it is far cheaper than fixing it after the test.

A weak answer: "We add metal around it until it passes." Follow-up: "It passes in the lab but customers report resets." Check immunity in the real installation: earthing, long cables and nearby drives.

Standards and safety

Which standards and marks, such as CE marking, does an electrical product need for the EU, the US and the UK?

What they check: that you know where the rules come from and plan them into the project.

Short answer: "For the EU, CE marking under EU law, usually under the EU Low Voltage Directive for equipment between 50 and 1,000 volts AC, the EU EMC Directive and the EU's RoHS rules on substances, plus the EU Radio Equipment Directive if it has a radio. The proof comes from harmonised EN standards, most of them based on IEC norms. In the US, customers usually ask for a UL listing in the US to the matching UL standard. The UK has its own UKCA mark in the UK."

The full answer: The product standard depends on the product: IEC 62368-1 for audio, video and IT equipment, IEC 61010-1 for lab and measuring equipment, IEC 60204-1 for the electrical equipment of machines; all are international IEC norms. In Germany, many appear as DIN VDE norms of the German VDE. The CB scheme of the IEC lets one test report count in many countries. Keep a technical file with the risk assessment and test reports, and plan the certification lab dates into the project from the start.

A weak answer: "CE is a sticker the manufacturer puts on." Follow-up: "The product will also be sold in the US." Plan the UL listing early: it may change parts, spacing and markings.

How do you design a product so it is electrically safe?

What they check: the basics of protection against electric shock and fire.

Short answer: "I keep users away from dangerous voltage with insulation, barriers and distances: basic insulation plus protective earth, or double or reinforced insulation without earth. On the board, the clearance and creepage distances of the product standard between mains and touchable parts. Fuses or breakers against overcurrent and fire, and parts rated for the voltage and temperature. Then a high-voltage test to prove the insulation."

The full answer: Start from the product standard and its risk assessment. Use certified safety parts, such as isolating transformers and mains connectors, where the standard asks for them. For machines, functional safety adds a further layer: ISO 13849 and IEC 62061, both international, rate how reliable a safety function such as an emergency stop must be. Work on installations in Germany is done or supervised by an Elektrofachkraft under the German DGUV rules.

A weak answer: "The power supply is bought in, so we are safe." Follow-up: "A tester finds the creepage too small near the relay." Add a slot in the board, move the parts, or choose a relay with wider spacing.

Testing

How do you test a new board before it goes to production?

What they check: a test plan from the first power-on to the production test.

Short answer: "Bring-up first: power on with a current limit, check every supply rail, the clocks and the reset, then program the microcontroller and test each block. Then design verification: every requirement measured over temperature and supply range, plus EMC and safety pre-tests. Last, a production test, so every board made later is checked automatically."

The full answer: Write the test plan with the requirements, not after the boards arrive. Environmental tests such as temperature cycling and vibration find weak solder joints and parts early. For production, combine a fast electrical test of the assembled board, such as in-circuit or flying probe tests, with a functional test that runs the board as in use. Automate the testsAsked in 8% of electrical engineer ads (as of 5 Nov 2026).Plan and run tests of firmware and boards, from bring-up to the production test. and keep the results, so trends show up before failures.

A weak answer: "If it powers up, it works." Follow-up: "There are only five prototype boards." Plan which tests may damage a board and run them last.

One board in a hundred fails in the field. How do you find the cause?

What they check: fault findingAsked in 10% of electrical engineer ads (as of 5 Nov 2026).Trace a fault through circuit, layout and firmware until the real cause is found. with data when a failure is rare.

Short answer: "I collect the failed boards and their history: batch, date, use and temperature. I compare failed and good boards, swap parts between them to see whether the fault moves, and test at the edges: hot, cold, low supply. Rare failures are often a worst-case tolerance, a marginal timing, a solder joint or a batch of parts, so I look at each."

The full answer: Use statisticsAsked in 0% of electrical engineer ads (as of 5 Nov 2026).Read the spread of measurements and test results, and judge whether a failure rate is real. before guessing: is the rate really higher in one batch or one installation? X-ray and cross-sections show solder problems. Check the design again against the worst case, with every tolerance at its limit. Once the cause is found, prove it by making the failure happen on purpose, then fix it and contain the boards already out there.

A weak answer: "One in a hundred is normal." Follow-up: "The failed boards work again on the bench." Recreate the field conditions: temperature, vibration, cable lengths and the real supply.

PLC and automation

How do you program and commission a PLC in TIA Portal?

What they check: structured PLC programming and a safe commissioning on site.

Short answer: "In Siemens TIA Portal I set up the hardware, the network and the tags, then build the program in function blocks: one per machine part, such as a conveyor or a valve group, reused where the parts are alike. I use the IEC 61131-3 languages that fit, ladder or function blocks for logic and structured text for calculations. I test in simulation first, then on site: every input and output checked, then each function, then the whole machine."

The full answer: A PLCAsked in 9% of electrical engineer ads (as of 5 Nov 2026).Program, test and commission PLCs, often Siemens S7 in TIA Portal, for machines and plants. program others can maintain has a clear structure, names, comments and alarms that tell the operator what is wrong. Safety functions run in a safety PLC with its own program and checks. The HMI, the operator screen, is designed with the operators. Commissioning follows a written plan, with a factory acceptance test at the maker and a site acceptance test at the customer, each signed off.

A weak answer: "I write the program on site, it is faster." Follow-up: "A sensor flickers and stops the line." Check the wiring and the sensor, then add a filter time in the program only if the signal itself is right.

How do you plan the electrical design of a control cabinet?

What they check: that you can turn a machine's needs into a cabinet that is safe, cool and can be built.

Short answer: "From the list of loads and signals: motors, drives, sensors and valves. I size the supply, the protection and the cables, plan the layout with power and control apart, and calculate the heat so the cabinet stays within its temperature. The schematic is drawn in a tool such as EPLAN or AutoCAD ElectricalAsked in 12% of electrical engineer ads (as of 5 Nov 2026).Schematics and panel layouts in an electrical CAD tool such as AutoCAD Electrical or EPLAN., so parts lists and wire lists come out of it."

The full answer: For machines in Europe, IEC 60204-1, published as EN 60204-1, sets the rules for the electrical equipment, and IEC 61439 covers the cabinet as an assembly; both are international. For the US, cabinets follow UL 508A in the US and machines NFPA 79 in the US, which changes parts and wiring. Plan space for later changes, and label every wire and terminal the same way as the drawing.

A weak answer: "The cabinet builder decides the layout." Follow-up: "The cabinet is too hot in summer." Measure, then add ventilation or a cooling unit, or move heat sources out.

FMEA and the lifecycle

How do you run an FMEA on an electronic design?

What they check: that you use FMEA to find weak points in a circuit before they reach the field.

Short answer: "An FMEA, failure mode and effects analysis, goes through the design and asks how each part or function can fail: open, short, drift or a wrong signal. For each I write the effect on the product, the cause, and how we would detect it. The worst combinations get actions, such as a protection circuit, a part with more margin or a test."

The full answer: Run it at the block level early and at the part level for critical circuits. Bring in the firmware, test and production teams, since many failures cross their borders. For functional safety, a deeper version, the FMEDA, adds failure rates to prove the safety level. Keep the FMEA alive inside the quality systemAsked in 4% of electrical engineer ads (as of 5 Nov 2026).Work inside the quality system: released schematics, change control, FMEA and 8D.: update it with every test failure and field return.

A weak answer: "We do the FMEA at the end for the customer." Follow-up: "Most entries are rated low risk." Ask for the evidence behind each rating.

A key part on your board will no longer be made. What do you do?

What they check: that you manage the lifecycle of parts, a daily worry in electronics.

Short answer: "First, how long we have and how many boards we still need, so we can decide on a last-time buy. Then a replacement: a drop-in second source if one exists, otherwise a small redesign, tested and released through the change process. And I check the rest of the parts list for other parts near the end of their life."

The full answer: Watch the notices that makers send before a part ends, and keep a list of risky parts. Design with second sources from the start where possible. A replacement needs the same tests as a new design for whatever it touches, and sometimes a new EMC or safety test. Agree the change with customers who must approve it.

A weak answer: "We will find one on the open market." Grey-market parts may be fakes. Follow-up: "There is no second source." Redesign the block and plan its tests and approvals into the timeline.

Senior electrical engineer, lead or principal engineer, engineering manager and head of engineering

These questions come up for senior electrical engineer, lead or principal engineer, engineering manager, head of engineering and technical director roles, where you answer for other people's designs and for the plan of a whole team.

As lead or principal engineer, how do you review the designs of other engineers?

What they check: technical leadershipAsked in 1% of electrical engineer ads (as of 5 Nov 2026).Lead engineers: plan the work, review designs, coach and take the hard technical calls.: reviews that catch problems and teach at the same time.

Short answer: "I review against the requirements and a checklist built from past problems: derating, protection, power and thermal, EMC layout, testability and the standards. I ask the designer to walk me through the design, ask questions rather than give orders, and write down every finding with an owner. Critical findings block the release; the rest are tracked."

The full answer: Review early, at the schematic, when changes are cheap, and again at the layout. Share the checklist so engineers check their own work first. Spot patterns across reviews and turn them into team standards. Praise good design choices in the same review; people learn from both.

A weak answer: "I fix the problems myself; it is faster." Follow-up: "The designer disagrees with a finding." Settle it with a calculation, a simulation or a test, not rank.

As engineering manager or head of engineering, how do you balance new products against fixing the old ones?

What they check: at the top of the ladder, that you can plan people and money across new work and support.

Short answer: "I make both visible: a road map for new products and a list of support work, such as field problems, part changes and cost cuts, with what each is worth. I set aside a share of the team for support, review the split each month with the managing director, and protect the new product teams from constant interruptions."

The full answer: Support work grows with every product sold, so plan it or it eats the road map. Fix root causes of repeated field problems once, rather than patching each case. Build standards, such as reference circuits, review checklists and test benches, that make the next product faster. Hire and grow leads, and presentPresent a design review or test results to managers and customers in a few clear slides. to the board the technical risk and what it costs.

A weak answer: "New products always come first." Follow-up: "A large customer has an urgent field failure." Form a small team to solve it fast, and tell the road map's owners what slips and why.

Your CV for these questions

An interviewer picks a design or a project from your CV and asks how you did it: the requirement, the choice, the measurement and the result. Lines like these, each placed under its own job, survive that kind of question:

A score against a real electrical engineer job marks the results the ad wants that your CV already proves, and the ones it still lacks.