निम्नलिखित कथनों पर विचार कीजिए : कथन I. सक्रियित कार्बन बहिःस्रावी धाराओं में से प्रदूषकों को हटाने और विभिन्न उद्योगों से आने वाले संदूषकों के उपचारण हेतु एक अच्छा और आकर्षक साधन है। कथन II. सक्रियित कार्बन का एक वृहत् पृष्ठ क्षेत्रफल होता है और उसमें भारी धातुओं को अधिशोषित करने की दमदार शक्यता है। कथन III. सक्रियित कार्बन, उच्च कार्बन अंश वाले वातावरणीय अपशिष्टों में से आसानी से संश्लेषित किया जा सकता है। उपर्युक्त कथनों के बारे में, निम्नलिखित में से कौन-सा एक सही है?

(b) कथन II और कथन III दोनों सही हैं किन्तु उनमें से केवल एक, कथन I की व्याख्या करता है

(c) कथन II और कथन III में से केवल एक सही है तथा वह कथन I की व्याख्या करता है

(d) न तो कथन II और न ही कथन III सही है

निम्नलिखित कथनों पर विचार कीजिए : कथन I. कुछ दुर्लभ मृदा तत्त्व, सपाट टेलीविजन स्क्रीन और कम्प्यूटर मॉनीटर के निर्माण में प्रयुक्त होते हैं। कथन II. कुछ दुर्लभ मृदा तत्त्वों में स्फुरदीप्त गुणधर्म होते हैं। उपर्युक्त कथनों के संदर्भ में, निम्नलिखित में से कौन-सा एक सही है?

(b) कथन I और कथन II दोनों सही हैं किन्तु कथन II, कथन I की व्याख्या नहीं करता है

(c) कथन I सही है किन्तु कथन II सही नहीं है

(d) कथन I सही नहीं है किन्तु कथन II सही है

प्रश्न यूपीएससी के हिंदी प्रश्नपत्र से · व्याख्या अभी अंग्रेज़ी में

English हिंदी

Science & technology

Prelims · Science & technology · 28 questions

Physics & chemistry in everyday life

Every UPSC Prelims question on this topic, 2016–2026, newest first. Tap an option to check yourself; the answer and explanation open below it.

Asked in 8 of 11 years · most in 2021 (4)

Practising Science & technology? Take it as timed sets of 25 →

UPSC syllabus: “General Science.” Sub-topics in the detailed syllabus →

Prelims 2025 · Q43

X-Ray · Core #44 Easy

विद्युत् वाहन बैटरियों के संदर्भ में, निम्नलिखित तत्त्वों पर विचार कीजिए :

I.कोबाल्ट
II.ग्रेफाइट
III.लिथियम
IV.निकेल

उपर्युक्त में से कितने सामान्यतया बैटरी के कैथोड बनाने के लिए उपयुक्त होते हैं?

Read this question in English

In the context of electric vehicle batteries, consider the following elements:

I. Cobalt

II. Graphite

III. Lithium

IV. Nickel

How many of the above usually make up battery cathodes?

(a) Only one · (b) Only two · (c) Only three · (d) All the four

उत्तर और व्याख्या · explanation in English

Answer: (c) केवल तीन

In a lithium-ion cell the cathode is a metal-oxide material built from lithium with nickel, cobalt (and manganese), as in the common NMC type. Graphite is the anode material, not part of the cathode. So three of the four elements make up cathodes.

✓ I Cobalt is one of the metals in the active cathode material.
✗ II Graphite forms the anode of the cell, not the cathode.
✓ III Lithium is a cathode mineral (the IEA lists lithium, nickel, cobalt and manganese for the cathode).
✓ IV Nickel is a main cathode metal; nickel-rich cathodes are a key trend in EV batteries.

Remember · EV battery cathode: lithium with nickel, cobalt (and manganese). Anode: graphite.

Sources

IEA: The Role of Critical Minerals in Clean Energy Transitions (2021), battery minerals ↗ · reference work “Cells typically account for 70% to 85% of the total battery weight, and contain a number of minerals in the active cathode material (e.g. lithium, nickel, cobalt and manganese), anode (e.g. graphite), and current collector (e.g. copper)”

Question and answer: UPSC's official GS Paper I (2025, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink ·

Prelims 2025 · Q44

X-Ray · Core #60 Easy

निम्नलिखित पर विचार कीजिए :

I.धूम्रपान के बाद सिगरेट के बचे हुए टुकड़े
II.चश्मे के लेंस
III.कार के टायर

उपर्युक्त में से कितनों में प्लास्टिक होता है?

Read this question in English

Consider the following:

I. Cigarette butts

II. Eyeglass lenses

III. Car tyres

How many of them contain plastic?

(a) Only one · (b) Only two · (c) All the three · (d) None

उत्तर और व्याख्या · explanation in English

Answer: (c) सभी तीन

All three contain plastic. Cigarette filters are made mainly of cellulose acetate fibres, which are microplastics; many eyeglass lenses are plastic (for example CR-39 and polycarbonate); and tiny plastic particles are shed by car tyres as they wear.

✓ I The WHO Framework Convention on Tobacco Control Secretariat says cigarette filters are mainly composed of microplastics known as cellulose acetate fibres.
✓ II Many spectacle lenses are made of plastic: a peer-reviewed study of spectacle lens materials covers CR-39, polycarbonate and Trivex, and calls CR-39 lenses the most basic form of plastic lenses.
✓ III IUCN counts particles worn off car tyres among the tiny plastic particles that reach the oceans.

Remember · Cigarette filters (cellulose acetate), eyeglass lenses (CR-39, polycarbonate) and car tyres (which shed microplastics) all contain plastic.

Sources

WHO Framework Convention on Tobacco Control Secretariat: World No Tobacco Day campaign raises alarm on tobacco industry environmental impact (31 May 2022) ↗ “These cigarettes contain filters mainly composed of microplastics known as cellulose acetate fibres.”
IUCN: Invisible plastic particles from textiles and tyres a major source of ocean pollution (22 February 2017) ↗ “Tiny plastic particles washed off products such as synthetic clothes and car tyres could contribute up to 30% of the ‘plastic soup’ polluting the world’s oceans”
Radiation protection properties of spectacle lens materials (peer-reviewed paper, hosted by NIH/PMC) ↗ “CR-39 lenses are the most basic form of plastic lenses, and the abbe value is the highest, which means that the optical quality is the best. … the radiation protection properties of spectacle lens (CR-39, Polycarbonate and Trivex) materials were investigated”

Question and answer: UPSC's official GS Paper I (2025, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 1 Oct 2026 (how we verify). Permalink ·

Prelims 2025 · Q45

Medium

निम्नलिखित पदार्थों पर विचार कीजिए :

I.एथेनॉल
II.नाइट्रोग्लिसरीन
III.यूरिया

उपर्युक्त में से कितनों के उत्पादन में कोयला गैसीकरण प्रौद्योगिकी प्रयुक्त की जा सकती है?

Read this question in English

Consider the following substances:

I. Ethanol

II. Nitroglycerine

III. Urea

Coal gasification technology can be used in the production of how many of them?

(a) Only one · (b) Only two · (c) All the three · (d) None

उत्तर और व्याख्या · explanation in English

Answer: (b) केवल दो

Coal gasification turns coal into syngas, which is then converted into fuels and chemicals. India's Ministry of Coal lists ethanol among these products and describes the Talcher plant converting syngas to ammonia and then urea. Nitroglycerine is made by nitrating glycerine with nitric and sulphuric acids and is not one of the coal-gasification products, so only two of the three qualify.

✓ I The Ministry of Coal includes ethanol among the liquid fuels made from syngas and notes that a policy change is under way to include ethanol from the coal gasification route.
✗ II Nitroglycerine (glyceryl trinitrate) comes from nitrating glycerine with mixed nitric and sulphuric acids; it is not a syngas product.
✓ III At Talcher, coal blended with pet-coke is gasified to syngas, converted into ammonia and then into urea.

Remember · Coal gasification gives syngas, then methanol, ethanol, ammonia and urea (Talcher fertiliser plant). Nitroglycerine comes from glycerine and nitrating acids, not from syngas.

Sources

Ministry of Coal: National Coal Gasification Mission (100 MT Coal Gasification by 2030), syngas products ↗ “Liquid Fuels such as Methanol, Ethanol, Synthetic diesel and Chemical and Petrochemicals like Methanol derivatives, Olefins, Propylene, Mono-Ethylene Glycol (MEG), nitrogenous fertilizers including Ammonia … Coal blended with pet-coke up to 25% shall be gassified to produce syngas, which shall be converted into Ammonia and subsequently to 1.27 Mt tonnes of neem coated Urea annually.”
PubChem (US National Library of Medicine, NIH), Nitroglycerin: Methods of Manufacturing (from HSDB) ↗ “It is prepared by continuous two-phase nitration of glycerol in anhydrous mixed acid. The mass ratio of pure anhydrous glycerol (H2O less than 0.5%) and 50:50 mixed acid is 1:5.”

Question and answer: UPSC's official GS Paper I (2025, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink ·

Prelims 2025 · Q50

Medium

निम्नलिखित कथनों पर विचार कीजिए :

कथन I: सक्रियित कार्बन बहिःस्रावी धाराओं में से प्रदूषकों को हटाने और विभिन्न उद्योगों से आने वाले संदूषकों के उपचारण हेतु एक अच्छा और आकर्षक साधन है।
कथन II: सक्रियित कार्बन का एक वृहत् पृष्ठ क्षेत्रफल होता है और उसमें भारी धातुओं को अधिशोषित करने की दमदार शक्यता है।
कथन III: सक्रियित कार्बन, उच्च कार्बन अंश वाले वातावरणीय अपशिष्टों में से आसानी से संश्लेषित किया जा सकता है।

उपर्युक्त कथनों के बारे में, निम्नलिखित में से कौन-सा एक सही है?

Read this question in English

Consider the following statements:

Statement I. Activated carbon is a good and an attractive tool to remove pollutants from effluent streams and to remediate contaminants from various industries.

Statement II. Activated carbon exhibits a large surface area and a strong potential for adsorbing heavy metals.

Statement III. Activated carbon can be easily synthesized from environmental wastes with high carbon content.

Which one of the following is correct in respect of the above statements?

(a) Both Statement II and Statement III are correct and both of them explain Statement I · (b) Both Statement II and Statement III are correct but only one of them explains Statement I · (c) Only one of the Statements II and III is correct and that explains Statement I · (d) Neither Statement II nor Statement III is correct

उत्तर और व्याख्या · explanation in English

Answer: (a) कथन II और कथन III दोनों सही हैं तथा वे दोनों कथन I की व्याख्या करते हैं

Both Statement II and Statement III are correct, and both explain Statement I. A large surface area lets activated carbon hold heavy metals and other pollutants on its surface, and because it can be made cheaply from carbon-rich waste, it becomes an attractive tool for cleaning effluents.

✓ II Activated carbon is highly porous, with a very large surface area and strong adsorption capacity. Pollutants stick to that surface (adsorption), which is exactly how it strips heavy metals from wastewater. This explains why it removes pollutants (Statement I).
✓ III Farm and other carbon-rich wastes are the usual raw material for activated carbon, and the process is simple and cheap. This low cost explains why it is 'attractive' as a treatment tool (Statement I).
✗ (b) This option says only one of II and III explains Statement I. But the ability to adsorb (II) explains the 'good' part and the cheap, waste-based supply (III) explains the 'attractive' part, so both explain it.
✗ (d) Both statements are supported by published research on biomass-derived activated carbon, so 'neither is correct' fails.

Remember · Activated carbon = porous, huge surface area, strong adsorbent, cheaply made from carbon-rich waste; hence widely used to clean effluents.

Sources

Adsorption of heavy metal onto biomass-derived activated carbon: review (RSC Advances, via NIH/PMC) ↗ “Biomass-derived activated carbon adsorbents offer large adjustable specific surface area, hierarchically porous structure, strong adsorption capacity, and excellent high economic applicability. … Agricultural waste is usually the first choice to prepare biomass-derived activated carbon, attributing to its high specific surface area, high stability, excellent adsorption properties, simple production process and low price.”

Question and answer: UPSC's official GS Paper I (2025, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink ·

Prelims 2025 · Q81

Medium

निम्नलिखित कथनों पर विचार कीजिए :

कथन I: कुछ दुर्लभ मृदा तत्त्व, सपाट टेलीविजन स्क्रीन और कम्प्यूटर मॉनीटर के निर्माण में प्रयुक्त होते हैं।
कथन II: कुछ दुर्लभ मृदा तत्त्वों में स्फुरदीप्त गुणधर्म होते हैं।

उपर्युक्त कथनों के संदर्भ में, निम्नलिखित में से कौन-सा एक सही है?

Read this question in English

Consider the following statements:

Statement-I. Some rare earth elements are used in the manufacture of flat television screens and computer monitors.

Statement-II. Some rare earth elements have phosphorescent properties.

Which one of the following is correct in respect of the above statements?

(a) Both Statement I and Statement II are correct and Statement II explains Statement I · (b) Both Statement I and Statement II are correct but Statement II does not explain Statement I · (c) Statement I is correct but Statement II is not correct · (d) Statement I is not correct but Statement II is correct

उत्तर और व्याख्या · explanation in English

Answer: (a) कथन I और कथन II दोनों सही हैं तथा कथन II, कथन I की व्याख्या करता है

Both statements are correct. Rare earth compounds such as europium and yttrium oxides act as phosphors, the light-emitting coatings that give colour in television and computer screens, so their luminescent property is exactly why they are used in displays.

✓ Statement-I IREL (India) Limited, a Department of Atomic Energy undertaking, lists television screens, computers and monitor displays among rare-earth uses; europium and yttrium oxides produce the red colour in television screens.
✓ Statement-II Rare earths have luminescent properties, and several (europium, terbium) are used as phosphors. That is why they light up screens, so this statement explains Statement-I.

Remember · Europium and yttrium oxides are rare-earth phosphors: their luminescence gives red (and, with europium, blue) colour in TV and phone screens.

Sources

FAQ on rare earths, IREL (India) Limited (Department of Atomic Energy) ↗ · reference work “Europium and Yttrium (oxides) produce the red colors in television screens and smart phone screens. … The REEs have unique catalytic, metallurgical, nuclear, electrical, magnetic and luminescent properties.”

Question and answer: UPSC's official GS Paper I (2025, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink ·

Prelims 2025 · Q85

X-Ray · Core #13 Medium

वायु प्रदूषण कम करने हेतु कृत्रिम वर्षा कराने के तरीके में किनका प्रयोग होता है?

Read this question in English

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

उत्तर और व्याख्या · explanation in English

Answer: (a) सिल्वर आयोडाइड और पोटैशियम आयोडाइड

Artificial rain is made by cloud seeding: seed particles are added to a cloud so that rain can form, and Delhi has trialled it as an emergency measure against pollution episodes. India's IITM names silver iodide as the standard seeding agent for cold clouds, and UPSC's key pairs it with potassium iodide.

✓ (a) Both agents are iodides. IITM's CAIPEEX pages name silver iodide (AgI) as the ice-nucleating agent used in glaciogenic seeding; UPSC's key names potassium iodide as the second agent, which the IITM pages do not mention.
✗ (b) Silver nitrate replaces silver iodide here; the key's answer has both agents as iodides.
✗ (c) Potassium nitrate replaces potassium iodide here; the key's answer has both agents as iodides.
✗ (d) Silver nitrate and potassium chloride replace both iodides.

Remember · Cloud seeding uses iodide salts, chiefly silver iodide (with potassium iodide in the key), to trigger rain.

Sources

Press Release: CAIPEEX, Scientific Cloud Seeding Experiment 2018, Indian Institute of Tropical Meteorology (Ministry of Earth Sciences) ↗ · reference work “A seeder and an instrumented research aircraft are being used to seed clouds and record the changes in clouds, leading to rainfall”
Indian Institute of Tropical Meteorology (Ministry of Earth Sciences), CAIPEEX cloud seeding FAQ (Misc. Publication 2024) ↗ · reference work “Glacigenic seeding: In a cloud with a temperature below freezing (0oC), typically, silver iodide (AgI) is used as the seeding agent, and the seeding method is called glaciogenic seeding.”
PIB (Ministry of Earth Sciences): Parliament question, Assessment of cloud seeding in Delhi, 5 February 2026 ↗ “At present, the cloud seeding activity is at trial stage with the objective to have one more option to provide relief as an emergency measure during episodic high air-pollution events when conducive cloud cover is present.”

Question and answer: UPSC's official GS Paper I (2025, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink ·

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