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Q1Science·Energy, Nuclear and Material SciencePYQ 2026
Which of the following statements with regard to stealth technology is/are correct?
1. Stealth objects have a very small radar cross-section and are coated with Radar Absorbing Material.
2. Stealth objects can be detected using specific frequencies.
3. Stealth objects are coated with metamaterials to increase the scattering of electromagnetic radiation.
Select the answer using the code given below:
- A1 only
- B2 and 3 only
- C1 and 2 onlyCorrect
- D1, 2 and 3
Why the other options are incorrect
- Option A
Statement 1 describes the main aim of radar stealth: reduce radar cross-section through shaping and radar-absorbing treatments. But it does not make an aircraft undetectable at every frequency, so statement 2 is also accepted.
- Option B
Statement 2 is accepted, but statement 3 reverses the intended effect of stealth treatments. Their purpose is to reduce the radar return toward a receiver through absorption or controlled redirection, not simply increase detectable scattering. Statement 1 should be included.
- Option D
The first two statements describe low observability and its limits, but statement 3 makes the combination incorrect. Metamaterials can manipulate electromagnetic waves in different ways; their use for stealth aims to suppress detection, not to make increased scattering toward radar the objective.
Q2Science·Energy, Nuclear and Material SciencePYQ 2026
Which of the following statements with regard to Green Hydrogen is/are correct?
1. It is decarbonized hydrogen obtained from natural gas reforming combined with carbon capture and storage (CCS).
2. It is produced using electrolysis of water with electricity generated by renewable energy.
3. National Green Hydrogen Mission of India aims for abatement of nearly 50 MMT of annual greenhouse gas emissions by 2030.
Select the answer using the code given below:
- A1 only
- B2 and 3 onlyCorrect
- C2 only
- D1, 2 and 3
Why the other options are incorrect
- Option A
Statement 1 describes blue hydrogen: hydrogen made from fossil feedstock with carbon capture and storage. Green hydrogen instead uses renewable energy, including renewable-powered water electrolysis, so statement 1 alone is not correct.
- Option C
Statement 2 is correct but does not exhaust the correct statements. The mission also projects nearly 50 MMT of annual emissions abatement by 2030, making statement 3 correct; this is an expected outcome, not a claim that the reduction has already occurred.
- Option D
The inclusion of statement 1 makes this option wrong. Carbon capture attached to natural-gas reforming does not turn that fossil-based route into renewable electrolysis; statements 2 and 3 are the correct pair.
Q3Science·Energy, Nuclear and Material SciencePYQ 2024
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?
- A1 and 2 only
- B2 and 3 onlyCorrect
- C1 and 3 only
- D1, 2 and 3
Explanation
Correct. RTGs rely on radioactive decay (not fission) to generate electricity for spacecraft, and they commonly use Plutonium-238 originally produced in weapons-grade reactor programmes.
Why the other options are incorrect
- Option A
Statement 1 is incorrect; RTGs convert heat from natural radioactive decay into electricity and do not involve fission chain reactions.
- Option C
Statement 1 is wrong because RTGs do not sustain a fission chain reaction; they use thermoelectric conversion of decay heat.
- Option D
Statement 1 is incorrect as RTGs are not fission reactors.
Q4Science·Energy, Nuclear and Material SciencePYQ 2023
Consider the following statements:
Statement-I: India, despite having uranium deposits, depends on coal for most of its electricity production.
Statement-II: Uranium, enriched to the extent of at least 60%, is required for the production of electricity.
Which one of the following is correct in respect of the above statements?
- ABoth Statement-I and Statement-II are correct and Statement-II is the correct explanation for Statement-I
- BBoth Statement-I and Statement-II are correct and Statement-II is not the correct explanation for Statement-I
- CStatement-I is correct but Statement-II is not correctCorrect
- DStatement-I is not correct but Statement-II is correct
Explanation
Correct. India does rely on coal for the bulk of its electricity despite having uranium reserves. However, nuclear power reactors use low-enriched uranium (about 3-5% U-235), not 60%.
Why the other options are incorrect
- Option A
Statement-II is factually wrong; power reactors use low-enriched uranium (3-5%), so it cannot explain anything.
- Option B
Statement-II is incorrect; nuclear power plants use uranium enriched to only about 3-5%, not 60%.
- Option D
Statement-I is correct; coal dominates India's electricity mix at over 70% of thermal generation.
Q5Science·Energy, Nuclear and Material SciencePYQ 2016
India is an important member of the 'International Thermonuclear Experimental Reactor'. If this experiment succeeds, what is the immediate advantage for India?
- AIt can use thorium in place of uranium for power generation
- BIt can attain a global role in satellite navigation
- CIt can drastically improve the efficiency of its fission reactors in power generation
- DIt can build fusion reactors for power generationCorrect
Explanation
Correct. ITER is an international project to demonstrate the feasibility of nuclear fusion as a large-scale energy source; success would enable India to build fusion reactors for power generation.
Why the other options are incorrect
- Option A
Thorium utilisation is part of India's three-stage nuclear programme and is unrelated to ITER, which focuses on fusion.
- Option B
ITER is a nuclear fusion project and has no connection to satellite navigation.
- Option C
ITER aims to demonstrate fusion, not to improve existing fission reactor efficiency.
Q6Science·Energy, Nuclear and Material SciencePYQ 2013
The known forces of nature can be divided into four classes, viz., gravity, electromagnetism, weak nuclear force and strong nuclear force. With reference to them, which one of the following statements is not correct?
- AGravity is the strongest of the fourCorrect
- BElectromagnetism acts only on particles with an electric charge
- CWeak nuclear force causes radioactivity
- DStrong nuclear force holds protons and neutrons inside the nucleus of an atom
Explanation
Correct. Gravity is actually the weakest of the four fundamental forces, not the strongest. The strong nuclear force is the strongest.
Why the other options are incorrect
- Option B
This is a correct statement; electromagnetic force acts on electrically charged particles.
- Option C
This is correct; weak nuclear force is responsible for beta decay (radioactivity).
- Option D
This is correct; the strong nuclear force binds protons and neutrons together in the nucleus.
Q7Science·Energy, Nuclear and Material SciencePYQ 2013
The efforts to detect the existence of Higgs boson particle have become frequent news in the recent past. What is/are the importance of discovering this particle?
1. It will enable us to understand as to why elementary particles have mass.
2. It will enable us in the near future to develop the technology of transferring matter from one point to another without traversing the physical space between them.
3. It will enable us to create better fuels for nuclear fission.
Select the correct answer using the codes given below.
- A1 onlyCorrect
- B2 and 3 only
- C1 and 3 only
- D1, 2 and 3
Explanation
Correct. The Higgs boson is associated with the Higgs field, which gives elementary particles their mass. Statements 2 and 3 are science fiction with no basis in the Standard Model.
Why the other options are incorrect
- Option B
Teleportation of matter and nuclear fuel improvement have no connection to the Higgs boson discovery.
- Option C
Statement 3 is wrong; the Higgs boson discovery has no application in creating nuclear fuels.
- Option D
Only statement 1 is scientifically valid; the other two are unfounded claims.
Q8Science·Energy, Nuclear and Material SciencePYQ 2011
The function of heavy water in a nuclear reactor is to:
- ASlow down the speed of neutronsCorrect
- BIncrease the speed of neutrons
- CCool down the reactor
- DStop the nuclear reaction
Explanation
Correct. Heavy water (D₂O) serves as a moderator in nuclear reactors, slowing down fast neutrons to thermal energies so they can sustain the fission chain reaction.
Why the other options are incorrect
- Option B
The moderator's purpose is to slow neutrons down, not speed them up.
- Option C
While heavy water may contribute to heat transfer, its primary role is as a moderator, not a coolant in this context.
- Option D
Heavy water sustains the chain reaction by moderating neutrons; control rods are used to stop or regulate the reaction.
Q9Science·Energy, Nuclear and Material SciencePYQ 2007
Four wires of same material and of dimensions as under are stretched by a load of same magnitude separately. Which one of them will be elongated maximum?
- AWire of 1 m length and 2 mm diameter
- BWire of 2 m length and 2 mm diameter
- CWire of 3 m length and 1.5 mm diameterCorrect
- DWire of 1 m length and 1 mm diameter
Explanation
Correct. Elongation = FL/(AY). This wire has the highest ratio of length to cross-sectional area (3 m / π(0.75 mm)²), producing maximum elongation.
Why the other options are incorrect
- Option A
Elongation is proportional to length and inversely proportional to cross-sectional area; this wire has a low L/A ratio compared to option (c).
- Option B
Although longer than (a), its larger diameter gives a lower L/A ratio than option (c).
- Option D
Despite the smallest diameter, the short length gives a lower L/A ratio than option (c).
Q10Science·Energy, Nuclear and Material SciencePYQ 1998
Match the names of outstanding Indian scientists given in List I with the area of their specialised work given in List II:
List I:
I. Dr. Raja Ramanna
II. Dr. M.S. Swaminathan
III. Prof. U.R. Rao
IV. Prof. Meghnad Saha
List II:
A. Plant Chemistry
B. Nuclear Physics
C. Thermodynamics and Astrophysics
D. Space Research
E. Agricultural Sciences
Select the correct answer using the codes given below:
- AI-B, II-E, III-D, IV-CCorrect
- BI-B, II-A, III-D, IV-C
- CI-C, II-E, III-B, IV-A
- DI-C, II-A, III-D, IV-B
Explanation
Correct. Raja Ramanna was a nuclear physicist; M.S. Swaminathan is the father of India's Green Revolution (agricultural sciences); U.R. Rao led India's space programme; Meghnad Saha is known for the Saha ionisation equation in thermodynamics and astrophysics.
Why the other options are incorrect
- Option B
M.S. Swaminathan's specialisation is agricultural sciences, not plant chemistry.
- Option C
Raja Ramanna was a nuclear physicist (B), not associated with thermodynamics and astrophysics (C).
- Option D
Multiple pairings are incorrect; Raja Ramanna was in nuclear physics and Meghnad Saha in thermodynamics/astrophysics.
Q11Science·Energy, Nuclear and Material SciencePYQ 1998
Which one of the following statements correctly describes the difference between a nuclear reactor and an atomic bomb?
- ANo chain reaction takes place in a nuclear reactor while in the atomic bomb there is a chain reaction
- BThe chain reaction in a nuclear reactor is controlledCorrect
- CThe chain reaction in a nuclear reactor is not controlled
- DNo chain reaction takes place in an atomic bomb while it takes place in a nuclear reactor
Explanation
Correct. In a nuclear reactor the chain reaction is controlled using moderators and control rods to sustain a steady energy output, whereas in an atomic bomb the chain reaction is uncontrolled and explosive.
Why the other options are incorrect
- Option A
Chain reactions occur in both; the difference is in how they are managed.
- Option C
This is the opposite of reality; the reactor chain reaction is controlled, not uncontrolled.
- Option D
Both involve chain reactions; in a bomb the reaction is uncontrolled and rapid.
Q12Science·Energy, Nuclear and Material Science
With reference to 'perovskite solar cells', consider the following statements:
1. They use a class of materials with a crystal structure similar to calcium titanium oxide.
2. They have shown rapid improvement in efficiency in recent years.
3. They are already more commercially widespread than silicon solar cells.
Which of the statements given above is/are correct?
- A1 only
- B1 and 2 onlyCorrect
- C2 and 3 only
- D1, 2 and 3
Explanation
Correct. Perovskite solar cells use the ABX₃ crystal structure and have seen dramatic efficiency improvements. Statement 3 is wrong; silicon cells still dominate the commercial market, while perovskites face stability and scaling challenges.
Why the other options are incorrect
- Option A
Statement 2 is also correct; perovskite cell efficiency has risen from about 3% to over 25% in roughly a decade.
- Option C
Statement 3 is incorrect; perovskite cells are still largely at the research and pilot stage.
- Option D
Statement 3 is wrong; commercial dominance remains firmly with silicon-based solar cells.