UPSC Essentials brings to you its initiative of subject-wise quizzes. These quizzes are designed to help you revise some of the most important topics from the static part of the syllabus. Attempt today’s subject quiz on Science and Technology to check your progress. Click Here to read the UPSC Essentials magazine for March 2026. Share your views and suggestions in the comment box or at manas.srivastava@indianexpress.com1. LPG is a gaseous fuel mix byproduct of crude oil refining and natural gas processing.2. Unlike LNG, LPG must be stored in cryogenic tanks and requires trained handling to prevent vapourisation or boil-off.3. In its liquid state, LNG occupies roughly 1/600th the volume of natural gas in gaseous form.4. Under relatively very high temperatures and pressure, the LPG mix becomes a liquid.How many of the statements given above are correct?(a) Only one(b) Only two(c) Only three(d) All fourStory continues below this adRelevance: LPG and LNG are key to understanding energy resources and fuel types, a frequently tested area in prelims. It helps in distinguishing between conventional fuels, storage methods, and transportation technologies. Such questions test conceptual clarity in physics and chemistry (liquefaction, pressure–temperature relations) applied to real-world energy use.Explanation:— LPG is a gaseous fuel mix primarily comprising propane and butane that is a byproduct of crude oil refining and natural gas processing. It may also contain some propylene, butylene, and isobutylene or isobutene. Hence, statement 1 is correct.— Under relatively low temperatures or moderate pressure, the gas mix becomes a liquid. It is mostly used for cooking and heating, with some industrial applications as well; it is also used as an automobile fuel in some parts of the world. LPG’s volume is around 1/260th of its gaseous volume. Hence, statement 4 is not correct.— LNG, on the other hand, is primarily natural gas — mainly methane — cooled to below -160 degrees Celsius and cryogenically turned into a liquid. Now, LNG itself doesn’t have too many direct uses, except for an upcoming fuel to power heavy vehicles, ships, and trains. The key purpose of liquefaction of natural gas into LNG is to transport it over long distances across seas, where supplying natural gas through pipelines is not feasible.Story continues below this ad— Unlike LPG, LNG must be stored in cryogenic tanks and requires trained handling to prevent vapourisation or boil-off. In its liquid state, LNG occupies roughly 1/600th the volume of natural gas in gaseous form, making it viable for transport and storage over long distances. The problem, though, is that this has to be done cryogenically, and is energy intensive. Hence, statement 2 is not correct and statement 3 is correct.— Essentially, LNG is natural gas that is liquefied for easier storage and transportation, and is mostly converted back to natural gas before being used. Natural gas itself has a number of applications — cooking fuel, transportation fuel, and industrial fuel or feedstock in sectors like refineries, fertilisers, power plants, and petrochemicals.Therefore, option (b) is the correct answer.QUESTION 2With reference to the working of the induction stoves, consider the following statements:1. The alternating current generates a rapidly fluctuating magnetic field directly above the cooktop.Story continues below this ad2. The change in the magnetic field passes through the glass surface and the surrounding air without heating either the surface or the air.Which one of the following is correct in respect of the above statements?(a) Both Statement 1 and Statement 2 are correct and Statement 2 is the correct explanation for Statement 1.(b) Both Statement 1 and Statement 2 are correct and Statement 2 is not the correct explanation for Statement 1.(c) Statement 1 is correct but Statement 2 is incorrect.(d) Statement 1 is incorrect but Statement 2 is correct.Story continues below this adRelevance: Induction stoves are a direct application of electromagnetic induction, a core concept in physics frequently asked in prelims. The topic links science with energy efficiency and clean cooking solutions, relevant for sustainable development questions.Explanation:— The war in West Asia has resulted in a severe disruption to cooking gas supplies in India and driven up the price of LPG cylinders. This has led to a surge in the sale of induction cooktops in the country.— Beneath the smooth ceramic or glass surface of an induction cooktop sits a tightly wound coil of copper wire. Switching the stove on completes the circuit and allows the flow of alternating current (AC) through the wire. The alternating current generates a rapidly fluctuating magnetic field directly above the cooktop. Hence, statement 1 is correct. The electronics and coil inside an induction cooker. (Wikimedia Commons)— This changing magnetic field passes effortlessly through the glass surface and the surrounding air without heating either the surface or the air. This allows the cooktop surface to largely maintain its temperature. Any warmth it acquires is from contact with the hot pan. Hence, statement 2 is correct.Story continues below this ad— So when the metal pan sits inside this intensely fluctuating magnetic field, it acts as a conductor. And localised, swirling electrical currents are generated inside the bottom of the pan itself. Known as eddy currents, these are pivotal to the heat-generation process.Both Statement 1 and Statement 2 are correct and Statement 2 is the correct explanation for Statement 1.Therefore, option (a) is the correct answer.QUESTION 3With reference to the uranium enrichment, consider the following statements:1. It is the process by which the concentration of Uranium-235 (U235) is increased in a sample of natural uranium.Story continues below this ad2. Most civilian nuclear reactors use “high enriched uranium” that’s been enriched to between 30 per cent and 50 per cent.3. The more the uranium is enriched, the smaller and lighter the weapon can be.How many of the statements given above are correct?(a) Only one(b) Only two(c) All three(d) NoneRelevance: Uranium enrichment is central to understanding nuclear fuel cycles and atomic energy, a recurring theme in prelims. It also connects with India’s energy strategy and institutions like the Department of Atomic Energy, often asked in science-based current affairs. The topic is relevant in the context of geopolitical developments involving countries like Iran and their nuclear programmes.Explanation:— Enrichment is the process by which the concentration of Uranium-235 (U235) is increased in a sample of natural uranium, which is primarily more than 99 per cent Uranium-238 (U238). U-235 has industrial applicability due to its fissile nature, meaning its nucleus can be broken down (or is fissionable) through a process that produces energy, and is capable of sustaining a chain reaction. Hence, statement 1 is correct.Story continues below this ad— The majority of civilian nuclear reactors use “low enriched uranium” that has been enriched to between 3% and 5%. This signifies that 3–5% of the uranium in the sample is now uranium-235. That is enough to sustain a chain reaction and generate power. Hence, statement 2 is not correct.— The higher the uranium enrichment, the smaller and lighter the weapon can be. Hence, statement 3 is correct.Therefore, option (b) is the correct answer.(Other Source: http://www.downtoearth.org.in)QUESTION 4Which of the following processes are used for the ethanol production from the cereal grains?1. Fermentation2. Polymerization3. Distillation4. dehydrationSelect the correct answer using the codes given below:(a) 1 and 2 only(b) 2, 3 and 4(c) 1, 3 and 4(d) 1, 2, 3 and 4Relevance: Ethanol production is central to India’s biofuel policy and energy transition, especially under the National Biofuel Policy. The topic connects agriculture (cereal grains, sugarcane) with industry, highlighting value addition and farmers’ income diversification. It also involves basic industrial processes in chemistry (fermentation, distillation), a common source of conceptual questions.Explanation:— Ethanol production involves fermentation of sugar by yeasts. In molasses or cane juice, sugar is present as sucrose. Cereal grains contain starch, a complex carbohydrate that has to first be extracted and broken down into simple sugars before further fermentation, distillation and dehydration to ethanol with 99.99% alcohol concentration.— Currently, ethanol is covered under the goods and services tax (GST) regime. The ethanol used for blending with petrol attracts 5% GST. But petrol remains outside GST, attracting both the Central excise duty and State value added tax. And both ethanol-blended petrol and pure petrol are treated as identical for taxation purposes.— Till 2017-18, ethanol was produced by distilleries attached to sugar mills only from so-called C-heavy molasses, a dark brown liquid byproduct of cane processing.— From 2018-19, mills began making ethanol from an earlier ‘B-heavy’ stage molasses (having higher sucrose content available for fermentation) and also directly from whole sugarcane juice or syrup. They were encouraged to do so by the Modi government’s decision to pay mills more for ethanol manufactured from the B-heavy and direct cane juice/syrup routes, in order to compensate them for the revenues foregone from lower/nil recovery and sale of sugar.— Polymerization is the formation of large molecules from monomers.Therefore, option (c) is the correct answer.QUESTION 5With reference to the Central Agro-Meteorological Observatory (CAgMO), consider the following statements:1. It has become the country’s first observatory to go fully digital.2. It is operated by the Ministry of Science and Technology.Which of the statements given above is/are correct?(a) 1 only(b) 2 only(c) Both 1 and 2(d) Neither 1 nor 2Relevance: The digital transformation of agro-meteorological observatories reflects India’s push toward technology-driven agriculture and precision farming, a key area in prelims. The topic links meteorology with agriculture, important for questions on climate services, monsoon dependency, and food security.Explanation:— Operated by the IMD, the Central Agro-Meteorological Observatory (CAgMO) in Pune has become the country’s first observatory to go fully digital. Hence, statement 1 is correct.— CAgMO is operated under the India Meteorological Department, which functions under the Ministry of Earth Sciences. Hence, statement 2 is not correct.— With this, the data coming out of the facility will be geo-tagged and instruments WiFi-enabled. Besides, all surface-based meteorological observations, such as temperature, rainfall, pressure, soil temperature and moisture, and wind speed, will be recorded by digital instruments in an automated manner.— Launching the “smart” observatory on Monday, on the occasion of World Meteorological Day, IMD Director General Mrutyunjay Mohapatra said, “This is a paradigm shift in the manner in which meteorological data, particularly the surface meteorological data, will be recorded. This demonstrates IMD’s strength and capabilities. We hope to digitise all the observatories in a time-bound manner as per our vision of Mission Mausam-2030.”Therefore, option (a) is the correct answer.Previous Daily Subject-Wise-QuizDaily Subject-wise quiz — History, Culture, and Social Issues (Week 150)Daily subject-wise quiz — Polity and Governance (Week 155)Daily subject-wise quiz — Science and Technology (Week 154)Daily subject-wise quiz — Economy (Week 154)Daily subject-wise quiz — Environment and Geography (Week 154)Daily subject-wise quiz – International Relations (Week 154)Subscribe to our UPSC newsletter and stay updated with the news cues from the past week.Stay updated with the latest UPSC articles by joining our Telegram channel – IndianExpress UPSC Hub, and follow us on Instagram and X.