UPSC Prelims Science & Technology previous year questions in the "Direct Conceptual / Factual MCQ" question pattern — real questions with answers and explanations.
2025Direct Conceptual / Factual MCQClean Energy & Materials
Artificial way of causing rainfall to reduce air pollution makes use of:
A.silver iodide and potassium iodide
B.silver nitrate and potassium iodide
C.silver iodide and potassium nitrate
D.silver nitrate and potassium chloride
Explanation: * Artificial rain (cloud seeding) is commonly conducted using silver iodide (Agl) and occasionally potassium iodide (KI). * These chemical compounds function as highly effective cloud condensation or ice nuclei, allowing water droplets to coalesce and precipitate as rain to clean the air.
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2024Direct Conceptual / Factual MCQBiotechnology & Healthcare
Which one of the following is synthesised in human body that dilates blood vessels and increases blood flow?
A.Nitric oxide
B.Nitrous oxide
C.Nitrogen dioxide
D.Nitrogen pentoxide
Explanation: * (a) Nitric oxide is correct: Nitric oxide (NO) is an essential cell-signaling molecule naturally synthesized within the endothelial lining of human blood vessels. It acts as a powerful vasodilator that relaxes vascular smooth muscle tissue, causing blood vessels to widen, which increases blood flow and safely modulates blood pressure.
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2024Direct Conceptual / Factual MCQClean Energy & Materials
Which one of the following is the exhaust pipe emission from Fuel Cell Electric Vehicles, powered by hydrogen?
A.Hydrogen peroxide
B.Hydronium
C.Oxygen
D.Water vapour
Explanation: * (d) Water vapour is correct: Fuel Cell Electric Vehicles (FCEVs) use onboard fuel cells to combine compressed hydrogen gas with atmospheric oxygen, generating electricity to drive an electric motor. This clean electrochemical process generates no toxic tailpipe pollution, releasing only pure water vapor and warm air as byproducts.
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2024Direct Conceptual / Factual MCQClean Energy & Materials
Recently, the term "pumped-storage hydropower" is actually and appropriately discussed in the context of which one of the following?
A.Field irrigation
B.Lift irrigation
C.Long duration energy storage
D.Rainwater harvesting
Explanation: * (c) Long duration energy storage is correct: Pumped-Storage Hydropower (PSH) is a configuration of two water reservoirs placed at different elevations. During periods of low power demand, cheap excess grid electricity is used to pump water up to the higher reservoir. When demand peaks, the water is released downward to spin turbines and generate power, acting as a massive, highly efficient long-duration utility energy storage system.
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2024Direct Conceptual / Factual MCQIT, AI & Electronics
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"?
A.Big data analytics
B.Cryptography
C.Metaverse
D.Virtual matrix
Explanation: * (c) Metaverse is correct: The term metaverse refers to a shared, immersive, and highly persistent network of 3D virtual spaces where multiple users interact via avatars. Powered by augmented reality, virtual reality, and blockchain networks, it allows user interaction, social/economic connections, and the assertion of property rights over distinct digital assets.
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