Now Reading
Many S&T Questions in UPSC Preliminary Exam Suffer From Conceptual Problems

Many S&T Questions in UPSC Preliminary Exam Suffer From Conceptual Problems

Photo: Nguyen Dang Hoang Nhu/Unsplash.

The civil services examination conducted by the Union Public Service Commission (UPSC) is one of the toughest in the world. The government uses it to select officers for administrative, police, foreign and other services.

It starts with a preliminary (‘prelims’) paper comprising objective tests used to qualify candidates for the main examination and interview.

In recent years, the nature of changes in the prelims question paper has come under scrutiny but the questions on core subjects have always remained free from debate. However, a closer look at the science and technology questions suggests some of them are just illogical.

While many questions related to science may not be debatable in a sense, grey areas emerge vis-à-vis their applications. For example, there is no question that graphene is a single layer of carbon atoms arranged in a two-dimensional honeycomb lattice. But whether we can use it to make transistors or specific sensors is the subject of ongoing research. As technology moves from laboratory tests to field tests, deployment and market acceptance, our perspectives keep changing.

So examination questions should avoid delving into such complex issues for the benefit of all stakeholders. Unfortunately, this is exactly what the UPSC has been doing: presenting aspirants with questions that contain a lot of grey areas, but whose answers are expected to be precise and specific.

Here are some examples from the 2020 prelims paper, followed by a brief analysis.

I. With reference to visible light communication (VLC) technology, which of the following statements are correct?

1. VLC uses electromagnetic spectrum wavelengths 375 nm to 780 nm

2. VLC is known as long-range optical wireless communication

3. VLC can transmit large amounts of data faster than Bluetooth

4. VLC has no electromagnetic interference

Select the correct answer using the code given below: (a) 1, 2 and 3 only (b) 1, 2 and 4 only (c) 1, 3 and 4 only (d) 2, 3 and 4 only.

Answer: (c)

Options 3 and 5 are misleading. Electromagnetic interference can be minimised but can’t be eliminated entirely in any communication setup that uses electromagnetic radiation.

In fact, whether VLC can transmit more data than Bluetooth depends on the kind of modulation used and instrumentation. According to current capabilities, Bluetooth is better than VLC on this front. For example, between two devices of comparable cost, Bluetooth will yield superior performance because it is not limited by line of sight limitations, whereas VLC is.

Of course, you can increase the cost and complexity to make one product better than another, from an engineering perspective, but technology is always driven by market costs and the UPSC should avoid delving into these contentious issues, especially in the confines of an examination question.

II. With the present state of development, artificial intelligence (AI) can effectively do which of the following?

1. Bring down electricity consumption in industrial units

2. Create meaningful short stories and songs

3. Diagnose diseases

4. Convert text-to-speech

5. Wirelessly transmit electrical energy

Select the correct answer using this code: (a) 1,2,3 and 5 only; (b) 1, 3 and 4 only; (c) 2, 4 and 5 only ;(d) 1, 2, 3, 4 and 5

Answer: (d)

The UPSC is wrong to think that (d) is correct. AI has no direct link to wireless transmission of electrical energy, although it can play a role if the transmission is automated and software-controlled. Then again, if this were so, AI can have applications in all the above areas! With the right algorithms and devices, AI can do almost anything – from changing babies’ diapers to building rocket engines. Such broad and vague questions have no use.

III. With reference to carbon nanotubes, consider the following statements:

1. They can be used as carriers of drugs and antigens in the human body

2. They can be made into artificial blood capillaries for an injured part of the human body

3. They can be used in biochemical sensors

4. Carbon nanotubes are biodegradable

Which of the statements given above are correct?

(a) 1 and 2 only; (b) 2, 3 and 4 only; (c) 1, 3 and 4 only; (d) 1, 2, 3 and 4

Answer: (d)

Words like “can be used” and “made” are vague. All potential applications of nanotubes are in the laboratory stage of development; from a commercial perspective, these structures are yet to find large-scale traction.

For example, there is no medically approved use of carbon nanotubes as drug-carriers or as artificial capillaries to this date because researchers haven’t yet fully understood their toxicity and potential mechanisms of reaction. At this stage, the only thing we can say with certainty is that carbon nanotubes are biodegradable. However, similar questions on nanotubes keep showing up every other year in the paper.

IV. Consider the following activities:

1. Spraying pesticides on a crop field

2. Inspecting the craters of active volcanoes

3. Collecting breath samples from spouting whales for DNA analysis

At the present level of technology, which of the above activities can be successfully carried out by using drones?

(a) 1 and 2 only; (b) 2 and 3 only; (c) 1 and 3 only; (d) 1, 2 and 3

Answer: (d)

It feels like the person setting the question did so after reading a particular news report, without attempting to understand the differences between engineering and technology. If you ask an engineer, they will say ‘of course drones can be used for all these things’. But do we have a cost-effective way to achieve them? As these technologies are in the early stages of development, a precise, definite answer to whether drones can inspect active volcanoes or collect samples from whales simply doesn’t exist.

The next question from medical science takes vagueness to a new height.

V. Consider the following statements:

1. Genetic changes can be introduced in the cells that produce eggs or sperms of a prospective parent

2. A person’s genome can be edited before birth at the early embryonic stage

3. Human induced pluripotent stem cells can be injected into the embryo of a pig

Which of the statements given above is/are correct?

(a) 1 only; (b) 2 and 3 only; (c) 2 only; (d) 1, 2 and 3

Answer: (d)

All these aspects are in different stages of development; the question could have included the context of the problem – e.g. laboratory stage, test stage, medically approved, etc. In medical science, or perhaps biology more broadly, a definitive statement is likelier to be true only in very specific contexts.

The UPSC expects its candidates to have knowledge of a broad spectrum of ideas but it’s disappointing that this isn’t matched with the knowledge of how or why something could be true.

VI. With reference to solar water pumps, consider the following statements:

1. Solar power can be used for running surface pumps and not for submersible pumps

2. Solar power can be used for running centrifugal pumps and not ones with pistons

Which of the statements given above is/are correct?

(a) 1 only; (b) 2 only; (c) both 1 and 2; (d) neither 1 nor 2

Answer: (b)

Option (b) as the answer is doubtful because the kind of pump is defined by the rating of the solar cells. Centrifugal pumps powered by solar power are quite popular in India but the question is about technological capability, not general utility. The use of the term “solar power” is also questionable because this could mean either solar photovoltaic systems or energy from solar concentration (which can be used to drive pumps with pistons – invalidating option 2).

As district collectors need know a lot about industrial waste, the following question is important:

VII. Steel slag can be the material for which of the following?

1. Construction of base road

2. Improvement of agricultural soil

3. Production of cement

Select the correct answer using the code given below:

(a) 1 and 2 only; (b) 2 and 3 only; (c) 1 and 3 only; (d) 1, 2 and 3

Answer: (d)

Examiners should avoid questions that imply definiteness where there is none on the utility front. Steel slag is a byproduct of steel-making, produced during the separation of molten steel from impurities in furnaces.

The slag occurs as a molten liquid melt and is a complex solution of silicates and oxides, and solidifies when cooled. In 2018, India’s steel ministry requested the agriculture ministry to look into using slag in the country’s eastern parts, where the soil is more acidic and productivity is lower. Researchers are still evaluating its use, including studying how plants accumulate heavy metals.

There was another agriculture-related question that appeared to be complex:

VIII. What is the use of biochar in farming?

1. Biochar can be used as a part of the growing medium in vertical farming

2. When biochar is a part of the growing medium, it promotes the growth of nitrogen-fixing microorganisms

3. When biochar is a part of the growing medium, it enables the growing medium to retain water for longer

Which of the statements given above is/are correct?

(a) 1 and 2 only; (b) 2 only; (c) 1 and 3 only; (d) 1, 2 and 3

Answer: (d)

It’s not clear what “growing medium” actually means. The medium does not grow; only the plant does. And whether biochar could be used in vertical farming depends on the nature of vertical farming. For example, if a setup uses hydroponics or aquaponics, biochar can’t be used.

According to a press release from the government of New South Wales, “Biochar has the potential to boost the natural ability of legumes to fix nitrogen to the soil, new research by [scientists] has revealed.”

Again, the examiner shouldn’t have included a question based on a couple studies conducted in the last few years – and should have waited under the studies’ results had been replicated.

We also keep hearing about blockchain and cryptocurrency, so the UPSC decided to throw in a question on this topic:

IX. With reference to “blockchain technology”, consider the following statements:

1. It is a public ledger that everyone can inspect, but which no single user controls

2. The structure and design of blockchain is such that all the data in it is about cryptocurrency only

3. Applications that depend on basic features of blockchain can be developed without anybody’s permission

Which of the statements given above is/are correct?

(a) 1 only; (b) 1 and 2 only; (c) 2 only; (d) 1 and 3 only

Answer: (a)

While the question and its answer are correct, the options are debatable. For example, #3 is about whether blockchain applications can be developed without approval. It’s common knowledge that applications can already be developed without anyone’s permission. You can buy a screwdriver, use it to make a nail and hang your clothes over it. The same thing applies to software.

Should UPSC ask such questions? Ideally, #3 should have been worded in terms of whether developers can add applications to the network without the approval of others on the same network.


These nine questions make up about a tenth of the total pool – and the bulk of which are ambiguous at best. Such questions are only bound to have a discouraging effect on those taking the test, since it appears that an honest attempt to apply the mind and answer them would just lead to a score of zero.

I myself could only get one answer correct, and I have had dozens of technical papers published in international journals and have conducted research for several years in many continents. I’m not clear if the questions in other parts of the paper are similarly flawed, but I wouldn’t be surprised if they are.

Dhiraj Sinha has a doctorate in electrical engineering from Cambridge University. He has published papers in the field of microsystems, electromagnetism and thermodynamics in international journals.

Scroll To Top