Overview
General Science is a critical component of UPSC Prelims and features in GS3 (Mains) under Science & Technology. The syllabus tests conceptual understanding rather than detailed technical knowledge — focus on principles, applications, and recent developments.
Physics Fundamentals
Newton's Laws of Motion
Published by Sir Isaac Newton in Principia Mathematica (1687), these three laws form the foundation of classical mechanics.
| Law | Statement | Application |
|---|---|---|
| First Law (Inertia) | Every object remains at rest or in uniform motion in a straight line unless acted upon by an external force | Seatbelts in cars — body continues forward motion during sudden braking |
| Second Law (F = ma) | The rate of change of momentum of a body is directly proportional to the force applied and takes place in the direction of the force | Rocket propulsion — thrust force accelerates the rocket as fuel mass decreases |
| Third Law (Action-Reaction) | For every action, there is an equal and opposite reaction | Walking — foot pushes ground backward, ground pushes foot forward |
Gravity
| Concept | Details |
|---|---|
| Newton's Law of Universal Gravitation | Every mass attracts every other mass with a force proportional to the product of their masses and inversely proportional to the square of the distance between them (F = Gm1m2/r2) |
| Gravitational Constant (G) | 6.674 x 10^-11 N m2/kg2 |
| Acceleration due to gravity (g) | 9.8 m/s2 on Earth's surface |
| Einstein's General Relativity (1915) | Gravity is not a force but the curvature of spacetime caused by mass and energy |
| Gravitational Waves | Ripples in spacetime; first detected by LIGO in September 2015 (announced February 2016) |
Electromagnetism
| Concept | Key Principle |
|---|---|
| Electric Charge | Two types — positive and negative; like charges repel, unlike attract |
| Coulomb's Law | Force between charges is proportional to product of charges and inversely proportional to square of distance |
| Electric Current | Flow of electric charge; measured in Amperes (A) |
| Magnetic Field | Generated by moving charges or changing electric fields |
| Electromagnetic Induction | Changing magnetic field induces electric current (Faraday's Law, 1831) — basis of generators and transformers |
| Electromagnetic Spectrum | Radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, gamma rays (increasing frequency and energy) |
| Maxwell's Equations | Unified electricity and magnetism into a single theory — light is an electromagnetic wave |
Nuclear Physics — Fission and Fusion
| Parameter | Nuclear Fission | Nuclear Fusion |
|---|---|---|
| Process | Heavy nucleus splits into two or more lighter nuclei | Two light nuclei combine to form a heavier nucleus |
| Fuel | Uranium-235, Plutonium-239 | Deuterium, Tritium (hydrogen isotopes) |
| Energy Source | Mass defect converted to energy (E = mc2) | Mass defect converted to energy (E = mc2) |
| Conditions | Requires neutron bombardment; chain reaction | Requires extremely high temperature (~150 million degC) and pressure |
| Example in Nature | None (artificial process) | Powers the Sun and all stars |
| Human Application | Nuclear power plants, nuclear weapons | Hydrogen bomb; experimental fusion reactors (ITER) |
| Waste | Produces long-lived radioactive waste | Minimal radioactive waste; produces helium |
| India's Programme | Three-stage nuclear programme (uranium, thorium cycle) | India is a member of the ITER project |
Semiconductors
| Concept | Details |
|---|---|
| Definition | Materials with electrical conductivity between conductors and insulators |
| Key Materials | Silicon (Si), Germanium (Ge), Gallium Arsenide (GaAs) |
| Types | Intrinsic (pure) and Extrinsic (doped) — n-type (excess electrons) and p-type (excess holes) |
| p-n Junction | Foundation of diodes — allows current flow in one direction |
| Transistor | Amplifies or switches electronic signals; basis of all modern electronics |
| Applications | Integrated circuits (chips), solar cells, LEDs, sensors |
| India's Semiconductor Mission | India Semiconductor Mission (ISM) launched to build domestic chip fabrication capacity |
Chemistry Fundamentals
Acids and Bases
| Property | Acids | Bases |
|---|---|---|
| Definition (Arrhenius) | Produces H+ ions in aqueous solution | Produces OH- ions in aqueous solution |
| Definition (Bronsted-Lowry) | Proton (H+) donor | Proton (H+) acceptor |
| Definition (Lewis) | Electron pair acceptor | Electron pair donor |
| Taste | Sour | Bitter |
| pH Range | Below 7 | Above 7 |
| Litmus Test | Turns blue litmus red | Turns red litmus blue |
| Examples | HCl, H2SO4, HNO3, acetic acid | NaOH, KOH, Ca(OH)2, NH3 |
pH Scale
| pH Value | Nature | Examples |
|---|---|---|
| 0–2 | Strongly acidic | Battery acid (~1), gastric acid (~2) |
| 3–4 | Moderately acidic | Lemon juice (~2.5), vinegar (~3) |
| 5–6 | Weakly acidic | Black coffee (~5), milk (~6.5) |
| 7 | Neutral | Pure water |
| 8–9 | Weakly alkaline | Seawater (~8.1), baking soda (~9) |
| 10–12 | Moderately alkaline | Milk of magnesia (~10.5), ammonia (~11) |
| 13–14 | Strongly alkaline | Bleach (~13), drain cleaner (~14) |
Periodic Table Trends
| Property | Trend Across a Period (Left to Right) | Trend Down a Group (Top to Bottom) |
|---|---|---|
| Atomic Radius | Decreases (more protons, stronger pull) | Increases (more electron shells) |
| Ionisation Energy | Increases (harder to remove electrons) | Decreases (outermost electron farther from nucleus) |
| Electronegativity | Increases (greater attraction for electrons) | Decreases |
| Metallic Character | Decreases | Increases |
| Electron Affinity | Generally increases | Generally decreases |
Polymers
| Type | Formation | Examples | Applications |
|---|---|---|---|
| Addition Polymers | Monomers add together without loss of atoms | Polyethylene (PE), PVC, Polystyrene, Teflon (PTFE) | Plastic bags, pipes, packaging, non-stick coatings |
| Condensation Polymers | Monomers combine with loss of small molecules (water) | Nylon, Polyester (PET), Bakelite | Textiles, bottles, electrical insulation |
| Natural Polymers | Produced by living organisms | Cellulose, starch, proteins, DNA, rubber | Food, clothing, biological functions |
| Biodegradable Polymers | Decompose naturally | PHA, PLA (polylactic acid) | Eco-friendly packaging, medical sutures |
Nanomaterials
| Property | Details |
|---|---|
| Definition | Materials with at least one dimension in the range of 1–100 nanometres |
| Unique Properties | Dramatically different optical, electrical, and mechanical properties due to high surface-area-to-volume ratio and quantum effects |
| Carbon Nanotubes | Cylindrical carbon molecules; extremely strong (100x steel at 1/6 weight); excellent electrical conductors |
| Graphene | Single layer of carbon atoms in hexagonal lattice; strongest material known; excellent conductor of heat and electricity |
| Quantum Dots | Semiconductor nanocrystals; used in displays, solar cells, medical imaging |
| Applications | Drug delivery, water purification, energy storage, electronics, coatings |
Biology Fundamentals
Cell Structure
| Component | Found In | Function |
|---|---|---|
| Cell Membrane | All cells | Selectively permeable barrier; regulates entry/exit of substances |
| Nucleus | Eukaryotic cells | Contains DNA; controls cell activities |
| Mitochondria | Eukaryotic cells | "Powerhouse of the cell" — produces ATP through cellular respiration |
| Chloroplast | Plant cells only | Photosynthesis — converts light energy to chemical energy |
| Ribosome | All cells | Protein synthesis |
| Endoplasmic Reticulum | Eukaryotic cells | Rough ER — protein transport; Smooth ER — lipid synthesis |
| Cell Wall | Plant, fungal, bacterial cells | Rigid outer layer providing structural support |
| Golgi Apparatus | Eukaryotic cells | Packaging, modification, and transport of proteins |
DNA and RNA
| Feature | DNA | RNA |
|---|---|---|
| Full Form | Deoxyribonucleic Acid | Ribonucleic Acid |
| Sugar | Deoxyribose | Ribose |
| Structure | Double-stranded helix | Usually single-stranded |
| Bases | Adenine, Thymine, Guanine, Cytosine (A-T, G-C pairing) | Adenine, Uracil, Guanine, Cytosine (A-U, G-C pairing) |
| Location | Primarily nucleus | Nucleus and cytoplasm |
| Function | Long-term storage of genetic information | Protein synthesis (mRNA, tRNA, rRNA) |
| Stability | Highly stable | Less stable; easily degradable |
Central Dogma of Molecular Biology: DNA ---(Transcription)---> RNA ---(Translation)---> Protein
Evolution
| Concept | Key Thinker | Description |
|---|---|---|
| Natural Selection | Charles Darwin (On the Origin of Species, 1859) | Organisms with traits better suited to environment survive and reproduce more — "survival of the fittest" |
| Inheritance of Acquired Characters | Jean-Baptiste Lamarck | Organisms pass on traits developed during their lifetime — largely disproven |
| Genetic Drift | Sewall Wright | Random changes in gene frequency in small populations |
| Mutation | Hugo de Vries | Sudden heritable changes in DNA — raw material for evolution |
| Punctuated Equilibrium | Gould & Eldredge | Long periods of stability punctuated by rapid evolutionary change |
Human Diseases
| Disease | Type | Causative Agent | Key Facts |
|---|---|---|---|
| Tuberculosis (TB) | Bacterial | Mycobacterium tuberculosis | India has the highest TB burden globally; BCG vaccine; DOTS treatment |
| Malaria | Parasitic | Plasmodium (via Anopheles mosquito) | P. falciparum is most lethal; no widely deployed vaccine until RTS,S (Mosquirix) |
| Dengue | Viral | Dengue virus (via Aedes aegypti mosquito) | No specific antiviral treatment; vector control is primary prevention |
| COVID-19 | Viral | SARS-CoV-2 | Pandemic since 2020; mRNA vaccines (Pfizer, Moderna), viral vector (Covishield), inactivated (Covaxin) |
| Diabetes | Metabolic/Non-communicable | Insulin deficiency (Type 1) or resistance (Type 2) | India is called the "diabetes capital of the world" |
| Cancer | Non-communicable | Uncontrolled cell division due to mutations | Leading cancers in India — lung, breast, cervical, oral |
Nutrition
| Nutrient | Function | Sources | Deficiency Disease |
|---|---|---|---|
| Vitamin A | Vision, immune function | Carrots, liver, dairy | Night blindness (Nyctalopia) |
| Vitamin B12 | Red blood cell formation, nerve function | Meat, dairy, eggs | Pernicious anaemia |
| Vitamin C | Collagen synthesis, antioxidant | Citrus fruits, amla | Scurvy |
| Vitamin D | Calcium absorption, bone health | Sunlight, fish, fortified milk | Rickets (children), Osteomalacia (adults) |
| Iron | Haemoglobin formation | Spinach, red meat, legumes | Anaemia |
| Iodine | Thyroid hormone production | Iodised salt, seafood | Goitre, cretinism |
| Protein | Growth, repair, enzymes | Pulses, eggs, meat, dairy | Kwashiorkor, Marasmus |
Immunity
| Type | Description | Examples |
|---|---|---|
| Innate Immunity | Non-specific, present from birth | Skin, mucous membranes, phagocytes, fever response |
| Adaptive (Acquired) Immunity | Specific, develops after exposure to pathogen | Antibody production, memory cells |
| Active Immunity | Body produces own antibodies | Vaccination, natural infection |
| Passive Immunity | Pre-formed antibodies received externally | Mother's milk (IgA), anti-venom, convalescent plasma |
| Herd Immunity | Community-level protection when sufficient proportion is immune | Achieved through vaccination programmes |
Recent Science Developments
Quantum Computing
| Aspect | Details |
|---|---|
| Principle | Uses quantum bits (qubits) that can exist in superposition (0 and 1 simultaneously) unlike classical bits (0 or 1) |
| Key Phenomena | Superposition, entanglement, quantum interference |
| Advantage | Exponentially faster for specific problems — cryptography, drug discovery, optimisation, climate modelling |
| Current Status | Google, IBM, and other companies developing quantum processors; "quantum advantage" demonstrated for specific tasks |
| India's Initiative | National Quantum Mission (NQM) approved in 2023 with Rs 6,003 crore outlay for 2023–2031 |
| Limitations | Extremely fragile (decoherence); requires near absolute zero temperatures; error rates still high |
Artificial Intelligence & Machine Learning
| Concept | Description |
|---|---|
| AI | Machines performing tasks that typically require human intelligence — reasoning, learning, problem-solving |
| Machine Learning | Subset of AI — algorithms that learn from data and improve without explicit programming |
| Deep Learning | Subset of ML using artificial neural networks with multiple layers |
| Natural Language Processing | AI understanding and generating human language (chatbots, translation) |
| Computer Vision | AI interpreting visual information (facial recognition, medical imaging) |
| Applications in India | Agriculture (crop disease detection), healthcare (diagnostics), governance (document processing), defence (surveillance) |
| Ethical Concerns | Bias in algorithms, job displacement, privacy, deepfakes, autonomous weapons |
Graphene
| Property | Details |
|---|---|
| Structure | Single layer of carbon atoms arranged in a two-dimensional hexagonal lattice |
| Discovery | Isolated in 2004 by Andre Geim and Konstantin Novoselov at the University of Manchester (Nobel Prize in Physics, 2010) |
| Strength | Strongest material ever measured — ~130 GPa tensile strength (about 200 times stronger than steel) |
| Conductivity | Excellent conductor of both electricity and heat |
| Flexibility | Highly flexible despite its strength |
| Applications | Flexible electronics, water filtration, energy storage (supercapacitors), biosensors, composite materials |
Hydrogen Fuel
| Aspect | Details |
|---|---|
| Principle | Hydrogen reacts with oxygen in a fuel cell to produce electricity, with water as the only by-product |
| Types | Grey hydrogen (from natural gas — CO2 emitted), Blue hydrogen (grey + carbon capture), Green hydrogen (from renewable energy electrolysis) |
| Advantages | Zero emissions at point of use; high energy density by weight; versatile fuel |
| Challenges | Production cost of green hydrogen; storage and transportation; lack of infrastructure |
| India's Initiative | National Green Hydrogen Mission (2023) — target of 5 million tonnes per annum (MTPA) of green hydrogen production by 2030; initial outlay of Rs 19,744 crore |
| Applications | Transportation (fuel cell vehicles), industrial decarbonisation (steel, refining, fertilisers), energy storage |
Important for UPSC
Prelims Focus
- Newton's three laws of motion and their applications
- Nuclear fission vs fusion — fuel, conditions, waste
- pH scale values for common substances
- DNA vs RNA — structure, bases, function
- Vitamins and deficiency diseases
- Graphene — discovery year (2004), Nobel Prize (2010)
- National Quantum Mission (2023) — outlay, duration
- National Green Hydrogen Mission — targets (5 MTPA by 2030)
Mains Dimensions
- Nuclear energy debate — India's three-stage nuclear programme, thorium reserves, safety concerns
- AI and governance — ethical use, bias, privacy, regulation
- Green hydrogen — role in energy transition, India's potential, challenges
- Semiconductor self-reliance — India Semiconductor Mission, geopolitical significance
- Nanotechnology applications — medicine, agriculture, environment
- Quantum computing — implications for cryptography, national security
Interview Angles
- "What is the significance of green hydrogen for India's climate goals?"
- "Should India invest more in nuclear energy or renewables?"
- "How can AI be used to improve governance while protecting privacy?"
- "What are the ethical challenges of genetic engineering?"
Previous Year Questions (PYQs)
Prelims
Q1. (2016): Which of the following is/are the example(s) of chemical change?
- Crystallization of sodium chloride
- Melting of ice
- Souring of milk
Select the correct answer using the code given below: (a) 1 and 2 only (b) 3 only (c) 1, 2 and 3 (d) None of the above Answer: (b) (Souring of milk is a chemical change involving bacterial action; crystallization and melting are physical changes) (Prelims PYQ, GS Paper I)
Q2. (2014): With reference to the properties of electromagnetic waves, consider the following statements:
- In electromagnetic spectrum, the wavelength of visible light is shorter than that of microwaves.
- Gamma rays have the shortest wavelength in the electromagnetic spectrum.
Which of the above statements is/are correct? (a) 1 only (b) 2 only (c) Both 1 and 2 (d) Neither 1 nor 2 Answer: (c) (Prelims PYQ, GS Paper I)
Q3. (2019): RNA interference (RNAi) technology has gained popularity in the last few years. Why?
- It is used in developing pest-resistant GM plants.
- It can be used for the treatment of diseases.
- It is used in the production of biofuels.
Select the correct answer using the code given below: (a) 1 and 2 only (b) 2 and 3 only (c) 1 and 3 only (d) 1, 2 and 3 Answer: (a) (RNAi technology is used in pest-resistant GM crops and has therapeutic applications; not primarily for biofuel production) (Prelims PYQ, GS Paper I)
Q4. (2015): In the context of heredity, consider the following statements:
- Both DNA and RNA carry genetic information.
- DNA is found in the nucleus of a cell while RNA is found only in the cytoplasm.
Which of the above statements is/are correct? (a) 1 only (b) 2 only (c) Both 1 and 2 (d) Neither 1 nor 2 Answer: (a) (Both DNA and RNA carry genetic information; however, RNA is found in both the nucleus and cytoplasm, not only cytoplasm) (Prelims PYQ, GS Paper I)
Mains
Q5. (2017): Discuss the work of 'Bose-Einstein Condensate' and its applications. Also examine the significance of India's contribution to this field. (GS Paper III, 250 words)
Q6. (2019): How is science interwoven deeply with our lives? What are the recent developments in science which can be used for the betterment of the human race? (GS Paper III, 250 words)
Current Affairs Connect
| Resource | Link |
|---|---|
| Ujiyari — General Science News | Ujiyari — General Science News |
| Ujiyari — Editorials | Ujiyari — Editorials |
| Ujiyari — Daily Updates | Ujiyari — Daily Updates |
Sources: NASA Glenn Research Center — Newton's Laws; Department of Atomic Energy (dae.gov.in) — India's Nuclear Programme; Ministry of New and Renewable Energy (mnre.gov.in) — National Green Hydrogen Mission; PIB — National Quantum Mission; MeitY — India Semiconductor Mission; WHO — Disease factsheets.