Quick Theory Capsule

Science & Technology (S&T) questions in Railway exams test three broad buckets:

1. Core Physics-Chemistry-Biology facts (Noble gases, cell organelles, Ohm’s law, pH scale, vaccines).
2. Everyday Applications—why sky is blue, how CFL saves power, MRI vs. CT scan, ultrasonic rail-flaw detection.
3. Contemporary & Government S&T Initiatives—Gaganyaan, Chandrayaan-3, 5G, Li-ion battery mission, National Super-computing Mission, hydrogen train, Kavach ATP, COVID vaccine types, DRDO’s ABHYAS drone.

Railways itself is a live lab: regenerative braking in 3-phase locos, GPS-based “Real-time Train Info”, fog-pilot assistance system, bio-toilets with anaerobic bacteria, solar-panel atop coaches, and “Head-on-Generation” (HOG) that saves 4 crore litre diesel/yr. Linking these real examples to textbook concepts is the examiner’s favourite trick.

Cheat-sheet thumb rules

• Nobel prizes & their years (Physics/Chem/Med) are asked verbatim—memorise last 5 yr winners.
• Acronyms: ISRO’s GSLV vs. PSLV, NASA’s JWST vs. LISA, DRDO’s Astra, BrahMos.
• “Firsts” in Indian space: 1st satellite (Aryabhata), 1st indigenous cryo engine (C25), 1st woman in space (Kalpana Chawla).
• Digital India: what is 5Gi, UPI, Digilocker, UMANG app—expect 1-liner facts.
• Environment linkage: LED saves 50-90 % energy, e-waste rules 2022, green crackers (CSIR-NESAC formula).

Practice MCQs

1. Which colour of light is scattered the most by atmospheric molecules?
   A. Red B. Yellow C. Blue D. Green

2. The working principle of a transformer is
   A. Joule’s law B. Faraday’s law of EMI C. Ohm’s law D. Lenz’s law only

3. Which gas is filled in the electric bulb to prolong filament life?
   A. O₂ B. CO₂ C. Argon D. Methane

4. The pH of human blood is approximately
   A. 6.4 B. 7.0 C. 7.4 D. 8.0

5. Which Indian satellite first carried an indigenous cryogenic upper stage?
   A. GSLV Mk III B. GSLV-D5 C. PSLV-C37 D. RISAT-1

6. The energy of 1 eV is closest to
   A. 1.6×10⁻¹⁹ J B. 1.6×10⁻²¹ J C. 9.1×10⁻³¹ J D. 6.6×10⁻³⁴ J

7. Which part of the cell is called its “transport department”?
   A. Lysosome B. Golgi body C. Ribosome D. Nucleus

8. The Kavach automatic train protection system uses which band?
   A. GSM-R B. ISM 2.4 GHz C. Ultra-sonic D. Optical fibre

9. Which vaccine type uses a harmless vector virus?
   A. Inactivated B. mRNA C. Viral-vector D. Toxoid

10. The specific resistance of a wire depends on
    A. length B. area C. material D. current

11. LED lights are preferred over CFL because
    A. emit IR B. contain mercury C. longer life & lower wattage D. operate at high voltage only

12. “Project 75 Alpha” recently approved by Govt. relates to
    A. Nuclear submarines B. Hydrogen trains C. Fighter jets D. Semiconductor fab

13. The main constituent of bio-gas is
    A. CO₂ B. H₂ C. CH₄ D. N₂

14. Which mirror is used as shop security mirror?
    A. Plane B. Convex C. Concave D. Cylindrical

15. 5G’s highest frequency band (mmWave) is roughly
    A. 600 MHz B. 2.1 GHz C. 3.5 GHz D. 28 GHz

16. A current-carrying conductor experiences a force in magnetic field; this is the principle of
    A. Electric motor B. Generator C. Transformer D. Thermocouple

17. The alloy used in railway track joints that expands minimally is
    A. Brass B. Invar C. Duralumin D. Solder

18. Which CRISPR pioneer won 2020 Chemistry Nobel?
    A. Doudna & Charpentier B. Zhang C. Banerjee D. Sharp

19. “Sodium lauryl sulphate” in toothpaste acts as
    A. Fluoride source B. Detergent & foaming agent C. Anti-bacterial D. Abrasive

20. The fastest supercomputer of India (2023) is
    A. Param Siddhi B. Pratyush C. Mihir D. Anupam-Varun

21. A train’s regenerative braking converts kinetic energy into
    A. Heat in rheostat B. Electrical energy back to grid C. Potential energy D. Sound

22. If a radioactive isotope has half-life 10 days, after 30 days remaining fraction is
    A. 1/2 B. 1/3 C. 1/8 D. 1/16

23. “Blue hydrogen” is produced by
    A. Electrolysis using renewables B. Steam methane reforming + CO₂ capture C. Coal gasification D. Bacterial fermentation

24. The minimum safe distance (km) between two trains protected by “Kavach” is
    A. 50 m B. 250 m C. 1 km D. 10 km

25. Which material is used in solar panel top-layer anti-reflection coating?
    A. SiO₂ B. MgF₂ C. TiO₂ D. Graphene

Shortcuts & Final Tips

• Rule of 72: Radioactive decay—divide 72 by half-life in days to get ≈ % left after 1 week.
• Fleming’s Left = Motor, Right = Generator—never mix directions.
• G-S-L-V: G (Geo, heavy), P-S-L-V: P (Polar, light) → remember “G for Geo-stationary, P for Polar”.
• pH scale rhyme: “0 Acid, 14 Base, 7 in the middle neutral face.”
• LED wattage swap: 9 W LED ≈ 15 W CFL ≈ 75 W bulb—always 1:1.6:8 ratio.
• Nobel trio: Physics → black holes & Peebles (2020), Chem → CRISPR (2020), Med → Hep-C virus (2020) — favourite RRB fact triplet.
• Kavach keywords: SIL-4 (highest safety integrity), GSM-R, 1 km, 3 sec reaction—fit in synonym MCQ traps.

Revise these 25 Qs twice; 20 % of RRB Science MCQs are verbatim lifts from previous year patterns. All the best!