Engineering · does it appeal?
Do you already wonder about any of this?
Fourteen questions about things you walk past every day. None of them are about careers, and none of them need anything you have not already been taught. The point is not the answers — it is whether working them out sounds like a good afternoon or a dull one. That reaction tells you more than any amount of reading about what engineers do.
Answers are still being checked. 0 of 14 answers are verified and shown below. Verified here means the answer has been checked against a standard, a datasheet or a published measurement, and cites it. Several of these deliberately have no single right answer — they are estimates, and the method is the answer — so those stay questions however long this page is up. That is not the page being unfinished. It is the difference between a question with a document behind it and a question you settle with a bucket and a stopwatch.
At home
Why does the fan slow down for a moment when someone starts the mixer?
Everyone in the house has seen it happen. Almost nobody has been told that the fan and the mixer are, in a real sense, the same appliance.
Answer being checked against the primary text before it goes up.
What answering it involves. Nothing runs on its own supply. Once you notice that every socket in the flat draws from one wire with a limit, the fan stops being a device and becomes part of a system — and asking what else is on the circuit is the first move an engineer makes on almost any problem.
Why is a phone charger warm, when the cable behind the fridge is not?
The fridge uses far more power than the phone. The small thing is the hot one, which is the wrong way round until you know what is being converted where.
Answer being checked against the primary text before it goes up.
What answering it involves. Heat is what you did not manage to use. Following energy through a machine — in here, out there, this much lost on the way — is bookkeeping rather than cleverness, and it transfers to every machine you will ever look at.
Why is your ceiling fan noisier than the identical one in the next room?
Same model, same shop, same day. One hums and one does not, and the difference is not that yours is broken.
Answer being checked against the primary text before it goes up.
What answering it involves. Nominally identical things are not identical. Everything made has a tolerance and everything installed has a mounting, and the gap between the drawing and the object is where a great deal of real engineering happens. It is also why a design that only works when everything is perfect is not a design.
Your phone
Full at eight, dead by four — in year three. Did the battery change, or did the phone?
A hundred per cent is still a hundred per cent. Something else moved, and working out what it must have been is doable from the outside, with no tools.
Answer being checked against the primary text before it goes up.
What answering it involves. A percentage is a ratio, and a ratio hides its own denominator. Asking "per cent of what, exactly" is the cheapest way there is to catch a claim that is true and misleading at the same time — on a battery, and on a placement brochure.
Why does the phone get hot in the one corner of the house where the signal is bad?
It is doing the same thing it does everywhere else, and only here does it cook. The reason is a decision it is making that you cannot see.
Answer being checked against the primary text before it goes up.
What answering it involves. Systems push back. Something is measuring the signal and turning the transmitter up until it is heard, so the heat is a symptom of a control loop rather than a fault. Finding the loop behind a symptom is most of what debugging anything is.
Why does WiFi reach one room fine and stop dead in the next?
The distance barely changed. What changed is what is in the way, and the walls that matter are not the ones you would pick.
Answer being checked against the primary text before it goes up.
What answering it involves. Reasoning about something invisible using only where it works and where it does not. You end up with a rough map of a thing you cannot see, built entirely out of evidence — which is what a measurement is, and a large part of the job.
Water and power
How much does the water in your roof tank weigh, and what is holding it up?
You can work this one out in your head in about a minute, and the answer is usually startling enough that people redo it to check.
Answer being checked against the primary text before it goes up.
What answering it involves. Estimation, at the moment it stops being an abstraction. A rough figure you can reach unaided tells you whether to worry at all — and noticing that a tank is a load carried by something is how you start seeing buildings as things holding themselves up rather than as shapes.
If the tank ran dry, how long would filling it by bucket from the ground floor take?
Nothing to look up. Guess first, then work it out, then notice how far off the guess was.
Answer being checked against the primary text before it goes up.
What answering it involves. A Fermi estimate: break an unanswerable question into four you can each guess within a factor of two. It is the most portable skill on this page, it needs no equipment, and it is how an engineer decides whether an idea is worth a week before spending the week.
A shock off a doorknob is thousands of volts and harmless. Mains is far less and kills. Why?
The number everyone quotes is the one that does not decide the outcome — worth understanding before you next open anything.
Answer being checked against the primary text before it goes up.
What answering it involves. The famous quantity is often not the governing one. Working out which variable actually decides an outcome, and being willing to set aside the one everybody names, is a move you will make in every problem for the rest of it.
Roads and traffic
Why does the pothole come back in the same spot every monsoon?
Not a different pothole. The same one, patched last year, and the patch is not the reason it came back.
Answer being checked against the primary text before it goes up.
What answering it involves. The difference between a symptom and a cause, in a form you can walk to. Water is getting somewhere it should not, and filling the hole treats the evidence rather than the mechanism — which is why the patch has a season and the road does not.
Would widening the road outside your school clear the morning jam?
The obvious answer is yes. The reason it is so often no is one of the most useful things anyone can tell you about systems, and it has little to do with roads.
Answer being checked against the primary text before it goes up.
What answering it involves. An intervention changes the behaviour it was measuring. Once you can hold "the fix changes what people do, and then the problem returns in a different shape" in your head, you stop trusting the obvious fix — in traffic, in software, and in anything with people inside it.
The lift moves at exactly the same speed at 8am. Why does it take so much longer?
Nothing about the machine changed. Everything about the queue did.
Answer being checked against the primary text before it goes up.
What answering it involves. Speed is not throughput, and the bottleneck is almost never the part that looks slow. Separating how fast one thing goes from how much gets through is what turns "it feels slow" into a problem with a number attached and a fix that works.
Things that are built
Why are there gaps in a flyover, and what happens if you close them?
The gaps are the bump you hear from inside a car. They are not sloppiness and they are not cheap — somebody paid extra to put them there.
Answer being checked against the primary text before it goes up.
What answering it involves. Designing for change rather than for a state. The bridge is a different size in May than in January, and the engineer's job was to decide where it is allowed to move. Choosing where a thing is permitted to give is a stranger and better question than making it rigid.
Why does a two-wheeler stay up while it is moving and fall over the moment it stops?
Everybody can ride one. Almost nobody can say what is holding it up, and the usual explanation is the wrong one.
Answer being checked against the primary text before it goes up.
What answering it involves. Stability is something a system does, not something it has. The bike is being continuously caught rather than balanced — the same idea as the phone turning its transmitter up, met in a completely different place. Recognising one idea in two unrelated objects is what makes the subject cohere.
What these have in common. Notice what these have in common. Almost none of them have an exact answer, and almost all of them turn into "roughly how much, and what gives way first". That is not the questions being vague. Being approximately right about the quantity that matters, today, beats being exactly right about one that does not — and if that sentence irritates you, it is genuinely useful to know now rather than in your second year.
Whether it is you
| Worth a closer look if… | Probably not, if… |
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Am I already late?
Almost certainly not, and the answer depends on where you are standing rather than on how much you have done.
| If you are in | Then |
|---|---|
| Class 10 | Nothing to prepare, and one thing not to do by accident. This is the field on this site where the Class 10 subject choice can close the door outright: without Mathematics in Class 11 and 12, every exam here is shut to you. Applied Mathematics is where it closes for people who never meant to close it — the subjects page has the detail, and it is worth ten minutes now rather than a year from now. |
| Class 11 | This is the year the preparation is actually done, whatever the coaching calendar implies. The entrance syllabus is drawn from both years in roughly equal measure, so starting in Class 12 means learning the Class 11 half while the Class 12 half is still arriving. If you are standing here and have not started, you are not late — you are exactly on time, which is the useful thing to know. |
| Class 12 | Not too late, but the shape of the decision has changed: you are choosing between exams now rather than adding them. Check the calendar for which papers collide with your boards, and read the exam pages for the eligibility traps — several of these carry subject and attempt conditions that get discovered far too late by people who assumed every exam works alike. |
Books, none of them preparation
The cheapest way to find out whether any of this interests you. None of these are preparation material and none of them will help you pass anything. If you find you cannot put one of them down, that is a better signal than any mock test.
| Book | Author | Why this one |
|---|---|---|
| The Way Things Work Now | David Macaulay | Everything from a zip to a power station, drawn and explained. Pitched below Class 10 and readable in pieces, which is the point — if you find yourself reading the pages you did not come for, that is the whole answer. |
| Structures: Or Why Things Don't Fall Down | J. E. Gordon | Why a bone, a bridge and a wing hold together, and what happens when they stop. The best book on this list, and funnier than its title admits. |
| To Engineer Is Human | Henry Petroski | Bridges and buildings that failed, and what was learnt from each one. Read it for the argument that failure is where the knowledge comes from, which is not how school treats being wrong. |
| The Design of Everyday Things | Don Norman | Why you push doors that say pull. It belongs here because it moves the question from "does it work" to "does it work for the person holding it", and that is a shift a lot of engineers never make. |
| Wings of Fire | A. P. J. Abdul Kalam with Arun Tiwari | What it looked like from inside a state engineering programme, written by someone who came into it without advantages. A memoir rather than a record — read it for what the work felt like, not for how the institutions run today. |
If that held your attention: where this field actually leads →
If you read these and caught yourself guessing a number before you had finished reading the question, that is worth paying attention to. If you read them and felt nothing, that is just as useful and it cost you four minutes. Neither reaction is the right one.