UPSC Prelims 2024 Science and Technology questions: topic-wise weightage
UPSC Prelims 2024 asked 8 science and technology questions in GS Paper I, spread over 3 topics. See the science and technology weightage for 2024 below, then attempt each question with the official answer and an explanation.
Science and Technology 2024: questions by topic
- Biology, health and biotechnology1
- Space technology3
- Physics and chemistry in daily life; energy and nuclear technology4
Counted from the 8 questions on this page, tagged by topic in the Battle IAS PYQ bank.
Seeing 8 Science and Technology questions spread over 3 topics can feel overwhelming. That's exactly why the Battle IAS PYQ Book maps every question topic by topic, so you know what to study first. Download free sample
Biology, health and biotechnology 1
Which one of the following is synthesised in human body that dilates blood vessels and increases blood flow ?
Answer (a) & explanation
Nitric oxide dilates blood vessels (a). The inner lining of blood vessels makes nitric oxide (NO) from the amino acid arginine. NO relaxes the smooth muscle in vessel walls, which widens them and increases blood flow, lowering blood pressure. Nitroglycerine for angina and drugs like sildenafil work through this pathway. Option (b) is wrong: nitrous oxide is laughing gas, used in anaesthesia and a greenhouse gas. Option (c) is wrong: nitrogen dioxide is a toxic air pollutant from vehicles. Option (d) is wrong: nitrogen pentoxide is an industrial chemical, not made by the body.
Notice that the discovery of NO as a body signal won the 1998 Nobel Prize in Medicine. Beetroot and leafy greens supply nitrates that the body turns into NO.
Answer as per the official UPSC answer key.
Space technology 3
Consider the following statements :
Statement-I : Giant stars live much longer than dwarf stars.
Statement-II : Compared to dwarf stars, giant stars have a greater rate of nuclear reactions.
Which one of the following is correct in respect of the above statements ?
Answer (d) & explanation
Statement I is wrong but Statement II is correct (d). Statement II is right: giant, massive stars have much hotter, denser cores, so their nuclear reactions run far faster than in small dwarf stars. Statement I is wrong: because they burn fuel so fast, giant stars live shorter lives. A very massive star may last only a few million years, while a small red dwarf can shine for trillions of years. More fuel does not mean a longer life: the faster burn rate wins.
Notice the endings: massive stars die in a supernova, leaving a neutron star or black hole. Sun-like stars swell into red giants and end as white dwarfs. The Chandrasekhar limit (about 1.4 solar masses) sets the maximum mass of a white dwarf.
Answer as per the official UPSC answer key.
Consider the following activities :
- 1. Identification of narcotics on passengers at airports or in aircraft
- 2. Monitoring of precipitation
- 3. Tracking the migration of animals
In how many of the above activities can the radars be used ?
Answer (b) & explanation
Radars can be used in two of the three (b). Item 2 is right: Doppler weather radars track rain, hail and storms, and help forecast cyclones; India's IMD runs a growing radar network, expanded under Mission Mausam (2024). Item 3 is right: the same radars pick up flocks of birds, bats and swarms of insects such as locusts on migration, and scientists use this to study them. Item 1 is wrong under UPSC's key: narcotics on passengers are found with X-ray and body scanners, chemical trace detectors and sniffer dogs, not radar.
Notice that radar stands for Radio Detection and Ranging. It bounces radio waves off objects, and the Doppler shift in the echo shows speed and direction.
Answer as per the official UPSC answer key.
Which one of the following words/phrases is most appropriately used to denote “an interoperable network of 3D virtual worlds that can be accessed simultaneously by millions of users, who can exert property rights over virtual items” ?
Answer (c) & explanation
This describes the metaverse (c). The metaverse is a persistent, shared, interoperable network of 3D virtual worlds that millions of users can enter at the same time, through VR/AR headsets or screens. Users can own virtual land and items, often recorded on blockchains as NFTs. Option (a) is wrong: big data analytics studies huge data sets for patterns. Option (b) is wrong: cryptography is the science of secure codes. Option (d) is wrong: "virtual matrix" is not a standard term.
Notice that the word comes from Neal Stephenson's 1992 novel Snow Crash. Facebook renamed itself Meta in 2021 to bet on it. The question's wording follows a widely cited definition by investor Matthew Ball.
Answer as per the official UPSC answer key.
Physics and chemistry in daily life; energy and nuclear technology 4
Consider the following :
- 1. Battery storage
- 2. Biomass generators
- 3. Fuel cells
- 4. Rooftop solar photovoltaic units
How many of the above are considered “Distributed Energy Resources” ?
Answer (d) & explanation
All four are Distributed Energy Resources (d). Distributed Energy Resources (DERs) are small units that generate or store power close to where it is used, often behind the consumer's meter, rather than at a big central plant. Battery storage (item 1) stores power for later. Biomass generators (item 2) make power from crop waste locally. Fuel cells (item 3) make electricity from hydrogen on site. Rooftop solar (item 4) is the most common DER. Micro-wind turbines and EV chargers that feed back power also count.
Notice the benefits: less power lost in long lines, more resilience during outages, and more renewables. India's PM Surya Ghar scheme (2024) aims at rooftop solar for one crore homes. Grouping many DERs together creates a virtual power plant.
Answer as per the official UPSC answer key.
With reference to radioisotope thermoelectric generators (RTGs), consider the following statements :
- 1. RTGs are miniature fission reactors.
- 2. RTGs are used for powering the onboard systems of spacecrafts.
- 3. RTGs can use Plutonium-238, which is a by-product of weapons development.
Which of the statements given above are correct ?
Answer (b) & explanation
Statements 2 and 3 are correct (b). Statement 2 is right: RTGs power the onboard systems of spacecraft, especially deep-space probes such as Voyager and New Horizons, and Mars rovers like Curiosity and Perseverance, where sunlight is too weak or dust blocks solar panels. Statement 3 is right: they use plutonium-238, made in reactors linked to weapons programmes. Statement 1 is wrong: an RTG is not a reactor and has no chain reaction. It turns the heat of natural radioactive decay into electricity through thermocouples.
Notice that India's Chandrayaan-3 lander carried small radioisotope heater units from BARC to test survival through the cold lunar night. Pu-238 has a half-life of about 88 years, giving decades of steady power.
Answer as per the official UPSC answer key.
In which of the following are hydrogels used ?
- 1. Controlled drug delivery in patients
- 2. Mobile air-conditioning systems
- 3. Preparation of industrial lubricants
Select the correct answer using the code given below :
Answer (a) & explanation
Hydrogels are used in controlled drug delivery (a). Hydrogels are networks of polymer chains that can soak up and hold large amounts of water while keeping their shape, like jelly. Item 1 is right: they are used for controlled drug release, letting medicine leak out slowly in the body. They are also used in soft contact lenses, wound dressings, nappies and to hold moisture in farm soil. Items 2 and 3 are not accepted by UPSC's key: hydrogels are not used in air-conditioning systems or in making industrial lubricants.
Notice the farm use: hydrogel granules mixed in soil soak up rain and release it to roots slowly, helping crops survive dry spells. India's Pusa Hydrogel, from IARI, is one such product.
Answer as per the official UPSC answer key.
Recently, the term “pumped-storage hydropower” is actually and appropriately discussed in the context of which one of the following ?
Answer (c) & explanation
Pumped-storage hydropower is discussed for long-duration energy storage (c). Pumped storage uses spare power, often cheap solar power at midday, to pump water up to a higher reservoir. At peak demand, the water is released through turbines to make electricity again. It works like a giant battery for long-duration storage, and helps fit variable renewables like solar and wind into the grid. Options (a), (b) and (d), about terrace farming, lift irrigation and rainwater harvesting, have nothing to do with it.
Notice India's push: the Power Ministry issued guidelines in 2023 to promote pumped storage projects. India has large potential, over 100 GW. Pumped storage makes up most of the world's grid storage today.
Answer as per the official UPSC answer key.
All years by topic
Every question from 2011 to 2026, grouped by syllabus topic, with year-wise trends.