A engineering interview to remember (Cambridge university engineering)

Since my unconditional undergrad offer to study engineering in Cambridge, I’ve never really found the time to write about my experience of the selection process and the interview I went through to be shortlisted. But heck it was really competitive, going against the top dogs in the best JCs in Singapore, not to mention scholars from around the region as well- A dinky neighborhood schooled and polytechnic student like me really felt out of place there, but I am glad I made the difference. I will just share part of the experience here.

The interview
The interviewer started by seeing me into the room after shaking hands and exchanging greetings. The room was set in a dimly lit incandescent atmosphere, very cozy, warm and casual, despite the presence of classroom florescent lights- which were left off. This is very unlike interviews we have in Singapore universities, particularly the one I went for scholarships where everything seem to be quite alot more ridged and authoritative.

We started with some icebreaker questions, the interviewer amusingly said that I was the first so far he had interviewed in Singapore who came from a polytechnic background, something very fresh and different from all the other A-level students he had interviewed so far. Though I do not want to draw any conclusions from that remark I guess I was a breakaway from the traditional stereotype which usually only makes up of junior college students.

So the questions, we started with quite a few general maths questions, followed by curve sketching. In my case, these were logarithmic curves and polynomials with or without asymptotes. I managed to get all of them sketched, but was stuck on the last. The interviewer, seeing that I was stuck nudged me in the right direction at times providing hints and we managed to solve the last one together. That came out quite without a hitch, though I do not really favor like such questions which can be done by memorizing math textbooks.

Next I was told that a large part of engineer’s work involves in the estimation of quantities, so I was told to calculate the mass of oxygen in the classroom we are in. Ahha! finally, a proper “thinking question”. That was fairly straight forward, but otherwise still quite linear as well. So digging from the depths of my cranium on thermodynamics, I managed to derive a formula using the ideal gas equation, with temperature, pressure constant and using the volume of air in the room (which can measured and calculated) to find the number of mols in the air, then multiplied by the constituent percentage of oxygen in the air and the relative atomic mass of a pair of oxygen atoms from the periodic table itself. And.. there’s the answer to “umm 3 s.f?” I exclaimed. The interviewer simply chuckled and nodded lightly on hearing that. Fair enough, but I guess no eye-brows raised from the interviewers though, then things started to be more interesting.

The interviewer then skimmed through my personal statement, impressed by the motion simulator I’ve built with my team in my polytechnic days, he asked me how it works, which I gladly explained using a sketch and some schematics I drew on the spot on an empty piece of paper between us- how it’s used for driving, for flight simulation, etc.

When done, the interviewer asked me how a plane flies. From here I came to realize that a bulk of the questions asked can depend largely on what your interests are and your statement, though such questions can also come randomly to anybody.

So I sat and thought a moment, I went about the need for the wings to generate enough lift or upthrust to counter the weight (W) of a plane through an ingenuous design of the wing which promotes a region of low pressure above the wing and a region of relatively higher pressure on the bottom of the wing. This is of course due to the differences in velocity the air particles will take to travel over the surface of the wing. The differences of the pressure creates a net resultant upward force, which translates to lift and causes a plane to fly. Thereafter I tied down the analogy to how a golf and cricket ball flies with the lift it creates by spinning as well, interesting way to expand on the question which could lead possibly anywhere thereafter.

Building on that, he told me that now I’ve got my plane in the air, how am I going to get the air moving fast enough for that to happen? I mentioned that it needed forward thrust from an engine which led to a question on how a plane engine works.

In that split second, at that moment the only thing I could think of was propeller planes, which lead me thinking of radial engines (typical in world war 2 planes and Harley Davidson motorcycles), so that means explaining how internal combustion piston engines work. That should be OK, but a propeller uses a “wing like” structure to produce trust which has an answer similar to the previous question as well, is that what the interviewer wanted? Despite all that which went though my mind at that instant, all I remembered saying was “Propeller engine?”

The interviewer smiled and told me the most favorite quote of the whole interview, while pointing to the plane sketch I have on the paper between us.

I simply went “huh?”. I was paused for a moment to process the new information, my mind was in a mess for that instant, then I calmed myself and then recalled that a jet engine is essentially a gas turbine engine. Then I recalled gas turbines running in helicopters, some formula boats, power stations as well as the M1 Abrams tank. I struggled to think of the components of the gas turbine which I knew I through general knowledge but could not remember it as that instant and the given interview pressure at that time.

Then calmly, I recalled a picture from memory of the engine of a Boeing 747 having a spinning turbo fan at the front of the engine, turbo fan equals air intake, which means a suction body to compress air- a compressor! So with a new stack of paper, I went on drawing an anatomy of a jet engine start from the front air compressor. A gas turbine is essentially a combustion engine, so I drew the combustion chamber after the compressor where the high pressure air and fuel mixture are ignited.

That was as far as I recalled. Then I fell back to my chair, stuck again knowing that there was a third and last part to it. Seeing that I was stuck, the interviewer hinted:

That lit the light bulb on my head- just like a piston engine which does work from the combustion stroke to push the piston down to spin the crankshaft, the gas turbine super-heated fuel needs to spin a shaft, how it does that is to run the superheated gases through another work turbine at the end which allows the shaft to do work (which in turns coupled to the intake turbine in a recurring process)! wowo!

I never formally studied a Jet engine in school, I was glad that went all well and I was on a roll- Thereafter we went on the applying (and deriving) the Newton Laws of motion on how it applies to our jet engine case where the exhaust gases produce thrust due to the action reaction pair (and transfer of momentum) between the plane and the surrounding air all with real life examples. Excellent!

Wrapping it up
Before we know it, “oh we are out of time” said the interviewer glancing at the room clock and turning back to the pile of sketched A4 papers between us (which I used to draw and illustrate the questions throughout the interview). Seeing that, I shrugged and started arranging the pile, remarking: “Mmmm maybe I should’ve… umm…. used less paper…”, then the interviewer laughingly said with a smile, “No, that was fine!”.

Time really passed very fast when you are having fun and I was surprised the interview lasted an actual 35-40 minutes while I thought only 15 has passed. The interviewer then asked about financial matters and my scholarship before opening questions from my side where he answered my queries regarding the annual solar eco-race for engineers, as well as the exchange program with MIT. In closing we shook hands again and the interviewer saw me out of the room before heading back in again.

Closing
The interview really turned out far better than what I thought it was to be, it was rather enjoyable as a matter of fact. In fact they were rather professional in keeping you cool and comfortable, it was a blast, so don’t worry about it. The interviewer really made me feel that Cambridge was a great fit for me and I am glad they saw it that way.

Looking back, I particularly like the way the interview is structured, particularly the general questions where anything under the sun related to your field can be asked, forcing you to think out of the box and within your comfort zone of what textbooks or what any dinky “ten-year series” can offer, which should be the case. Remember, the interview aims to test your “unlearnt knowledge”, so the best is to go in as yourself with an open mind, that is the best advice I can give when I come to realize after the interview. Each interview is of course unique to the applicant and will differ.

Hehheh I hope my college director of studies won’t go after me for sharing this interview here. So if you are reading this in preparations for yours, I hope this experience will provide you an eye opener on what to expect in yours.

All the best and have a great interview!