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Free practice questions, preparation advice, and expert insights for Electrical Engineering interviews at Imperial College London.
Real Electrical Engineering interview questions in the style Imperial College London asks. Try answering each one aloud before you reveal the hint.
A 12 V battery drives current through two resistors, a 4 kΩ and a 2 kΩ, connected in series. Work out the current in the loop and the voltage dropped across each resistor. Now what happens to the current if I put the two resistors in parallel instead?
Problem-Solving
Hint
Start from Ohm's law and add series resistances before dividing; for the parallel case reason qualitatively that total resistance falls, so current from the battery rises, before reaching for the reciprocal formula.
A capacitor is charged through a resistor from a fixed DC supply. Sketch the voltage across the capacitor against time and explain the shape. What single quantity sets how fast it charges, and how would you change the circuit to make it charge twice as quickly?
Problem-Solving
Hint
Identify the RC time constant, explain the exponential approach to the supply voltage, and note that halving either R or C halves the time constant.
A sinusoidal signal is passed through a circuit made of one resistor and one capacitor. At very low frequencies the output equals the input; at very high frequencies the output is tiny. What is this circuit doing, and roughly where is the turning point on the frequency axis?
Problem-Solving
Hint
Recognise a first-order low-pass filter, reason about the capacitor's impedance falling with frequency, and locate the cut-off where the reactance equals the resistance.
You are told a length of wire has resistance R. Without doing any experiment, predict how the resistance changes if I double its length, and separately if I double its diameter. Which change matters more?
Problem-Solving
Hint
Use the resistivity relation, keep length and cross-sectional area separate, and remember area scales with the square of the diameter.
A signal is sampled by a computer at a fixed rate. If the incoming signal contains a frequency higher than half the sampling rate, something goes wrong. Reason your way to what happens, and tell me what a designer should put in front of the sampler to prevent it.
Problem-Solving
Hint
Arrive at aliasing and the Nyquist limit from first principles, then propose an analogue anti-aliasing low-pass filter before the sampler.
Structured interviews that combine technical problem-solving with motivation and personal statement discussion.
Imperial interviews vary by department. Engineering and Computing tend to be technical with problem-solving elements. Medicine uses a Multiple Mini Interview (MMI) format with several short stations. Most interviews last 15-30 minutes and may include a presentation or group exercise.
Interview Invitation
Late Nov
Arrival to Interview
Early Dec
Technical Question
Mid Dec
Decision
Early Jan
Interview Invitation
Late Nov
Arrival to Interview
Early Dec
Technical Question
Mid Dec
Decision
Early Jan
When you flick a light switch the lamp seems to come on instantly, yet the electrons in the wire drift only millimetres per second. Reconcile those two facts for me.
midHint
Separate the slow drift velocity of individual charge carriers from the fast propagation of the electromagnetic field and the near-simultaneous push on charges all along the wire.
Explain, in your own words, why a changing magnetic field produces a voltage but a steady one does not. Where in everyday electrical engineering does this actually matter?
midHint
Reach Faraday's law of induction, emphasise the rate of change of flux, and connect it to transformers, generators or inductors.
A diode conducts current in one direction but not the other. Without invoking any equation you have memorised, argue physically why a junction between two differently doped pieces of silicon should behave this way.
hardHint
Build up the p-n junction picture: doping, the depletion region, the built-in field, and how forward versus reverse bias either shrinks or widens that barrier.
Engineers often say a system is 'linear'. What do they mean by that, and why do they care so much? Give me an example of an electrical component that is decidedly not linear.
hardHint
Define linearity through superposition and scaling, explain why it makes analysis tractable, and cite a nonlinear device such as a diode or transistor.
Why do the National Grid and long-distance power lines run at very high voltages, when the appliances in your home run at 230 volts? What is the engineering pay-off, and what is the cost of that choice?
midHint
Link transmitted power to the product of voltage and current, argue that higher voltage means lower current and lower resistive losses, then note insulation and safety costs.
Your statement mentions a hands-on electronics or coding project. Talk me through what it actually does, then pick the single hardest technical decision you faced and defend the choice you made.
entryHint
Show genuine ownership: describe the aim and principle concisely, then reason openly about a real trade-off rather than presenting the project as flawless.
You could have applied for physics, computer science or general engineering. Why specifically Electrical and Electronic Engineering, and why at Imperial rather than elsewhere?
entryHint
Connect the discipline's blend of physical principles and systems design to concrete interests, and reference specifics of the course structure rather than reputation alone.
Tell me about a piece of reading, a video or an article beyond your syllabus that changed how you think about electronics or electrical systems. What did you disagree with or want to probe further?
midHint
Demonstrate critical engagement, not just recall: say what shifted in your understanding and pose a genuine follow-up question of your own.
Electrical and Electronic Engineering spans electromagnetism, devices, signals, power, embedded systems and software. Which of these currently pulls at you most, and which do you know least about? Be honest.
midHint
Show awareness of the breadth of the field and intellectual honesty about gaps, avoiding a narrow gadget-only presentation.
Estimate how many mobile-phone base stations there are in the United Kingdom. Reason out loud; I care about your assumptions, not the exact number.
midHint
Break the problem into population, coverage cells and typical cell radius, state each assumption clearly, and sanity-check the final order of magnitude.
Suppose electrical resistance suddenly vanished from every material in the world. Pick two consequences for how we design electronic and power systems, and reason them through.
hardHint
Explore superconductivity-like implications: no resistive heating, no simple voltage dividers, and the loss of components engineers rely on to control current.
I hand you a sealed black box with two terminals. You may connect a battery, an ammeter, a voltmeter and a signal generator. How would you work out what is inside it?
hardHint
Design an experimental strategy: DC behaviour to distinguish resistor from capacitor or inductor, then frequency response to reveal reactive or nonlinear elements.
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