RRB Technician Grade III 2024, 2025 PYQs

Concept: Glass is optically denser than air, and its refractive index differs for each colour.

1. White light splits into VIBGYOR, so (i) is true
2. Light slows down in a denser medium ($v=\frac{c}{n}$, $n\approx 1.5$ for glass), so (iii) is true and (ii) is false

Trick: (ii) and (iii) contradict each other, so only one can be true. Speed falls in glass, so the answer is (i) + (iii).

Answer: (B) Both (i) and (iii)

Concept: $\text{Power}=\frac{\text{Work}}{\text{Time}}=\frac{\text{Weight}\times \text{height}}{\text{time}}$.

1. Work = $420\text{N}\times 6\text{m}=2520\text{J}$
2. Power = $2520÷20=126$ W

Trick: Weight is already in newtons, so do not multiply by g again: $P=\frac{W\times h}{t}$ directly.

Answer: (A) 126 W

Concept: Alcohol + carboxylic acid → ester (sweet smell) + water, in the presence of conc. H₂SO₄.

1. CH₃COOH + C₂H₅OH → CH₃COOC₂H₅ (ethyl ethanoate) + H₂O
2. Conc. H₂SO₄ acts as a catalyst and removes the water formed (dehydrating agent), which pushes the reaction forward

Trick: Sweet smell = ester, so the reaction is esterification. Only option C names it.

Answer: (C) It is an esterification reaction; H₂SO₄ acts as a catalyst and a dehydrating agent.

Concept: Energy released depends on how completely glucose is broken down.

1. Anaerobic: glucose is only partly broken down to ethanol + CO₂ or lactic acid, giving 2 ATP
2. Aerobic: glucose is fully oxidised to CO₂ + H₂O, giving about 36–38 ATP
3. Both use enzymes, so A is wrong

Yaad rakhein: Yeast gives ethanol + CO₂; tired muscles give lactic acid (which causes cramps).

Answer: (B) It partially breaks down glucose.

Concept: Speed of a wave v = frequency × wavelength; time = distance/speed.

1. $v=2000\text{Hz}\times 0.45\text{m}=900\text{m/s}$
2. $t=1800\text{m}÷900\text{m/s}=2\text{s}$

Trick: Convert units first: 2 kHz = 2000 Hz, 45 cm = 0.45 m, 1.8 km = 1800 m.

Answer: (A) 2 seconds

Concept: $F=\frac{G{m}_1{m}_2}{r^2}$, so $G=\frac{F{r}^2}{m_1{m}_2}$.

1. Unit = $\frac{\text{N}\times {\text{m}}^2}{{\text{kg}}^2}$
2. $=\text{N}{\text{m}}^2{\text{kg}}^{-2}$

Yaad rakhein: $G=6.67\times {10}^{-11}\text{N}{\text{m}}^2{\text{kg}}^{-2}$; it is the same everywhere in the universe, unlike g.

Answer: (A) Nm2kg-2

Concept: Epithelial tissue covers body surfaces and lines organs.

1. It forms a protective covering (skin, lining of mouth)
2. Glandular epithelium secretes substances (e.g. sweat, enzymes)
3. Coordination is done by nervous tissue, support by connective tissue, contraction by muscle

Yaad rakhein: Types: squamous (skin, lungs), cuboidal (kidney tubules), columnar (intestine), ciliated, glandular.

Answer: (B) Secretion and protection

Concept: A more reactive element displaces a less reactive one from its compound.

1. A displaces B, so A > B
2. C displaces A, so C > A
3. Order: C > A > B

Trick: The displacer is always on the left: chain the two clues as C > A > B.

Answer: (B) C > A > B

Concept: Groundwater is stored in porous water-bearing layers (aquifers).

1. A dug well draws water that seeps from the water-bearing strata around it
2. Impervious strata (clay, hard rock) do not let water through, so they cannot supply a well

Yaad rakhein: The upper level of groundwater is called the water table; it falls when we take out more water than rain recharges.

Answer: (C) Water-bearing strata

Concept: Only about 10% of energy passes from one trophic level to the next.

1. About 90% is lost as heat and in life processes at each level
2. After 4 levels, too little energy remains to support another level

Trick: 10% law: 1000 J → 100 → 10 → 1 J. By the 4th level almost nothing is left.

Answer: (D) of large loss of energy at each level

Concept: Lens formula: $\frac{1}{v}-\frac{1}{u}=\frac{1}{f}$; magnification $m=\frac{v}{u}$.

1. $u=-20$ cm, $f=+15$ cm: $\frac{1}{v}=\frac{1}{15}-\frac{1}{20}=\frac{1}{60}$, so $v=+60$ cm
2. $m=\frac{60}{-20}=-3$ (real, inverted, 3 times enlarged)

Trick: The object is between f and 2f (20 cm lies between 15 and 30 cm), so the image is real, inverted and magnified: m must be negative with $|m|>1$, which is −3.

Answer: (B) -3

Concept: The pistil (carpel) is the female reproductive part.

1. Pistil = stigma + style + ovary (ovules inside)
2. Stamen (anther + filament) is the male part; sepals and petals are non-reproductive

Yaad rakhein: After fertilisation the ovary becomes the fruit and the ovules become seeds.

Answer: (D) pistil

Concept: Thumb, first finger and middle finger are held mutually perpendicular.

1. First (index) finger = magnetic Field
2. Middle finger = Current
3. Thumb = Motion (force on the conductor)

Trick: FBI order: F (thumb) = Force, B (index) = magnetic field, I (middle) = current. Or 'Father, Mother, Child' = Motion (thumb), Field (first), Current (middle).

Answer: (C) First (index) finger

Concept: $R=\frac{V}{I}$.

1. $R=1\text{V}÷1\text{A}$
2. $=1\Omega$

Yaad rakhein: This is the definition of 1 ohm: the resistance of a conductor through which 1 A flows when 1 V is applied across it.

Answer: (D) 1 Ω

Concept: Add the atomic masses: N = 14, H = 1, S = 32, O = 16 u. The formula is $({\text{NH}}_4{)}_2{\text{SO}}_4$.

1. $2\times {\text{NH}}_4=2\times (14+4)=36$
2. ${\text{SO}}_4=32+4\times 16=96$
3. Total = $36+96=132$ u

Trick: Remember ${\text{NH}}_4=18$ and ${\text{SO}}_4=96$ (${\text{H}}_2{\text{SO}}_4=98$, take away 2 H). So $2\times 18+96=132$.

Answer: (C) 132 u

Concept: Acid + base → salt + water; H⁺ and OH⁻ cancel each other.

1. When neutralisation is complete, the solution is neither acidic nor basic, so pH ≈ 7
2. The reaction is exothermic, so the temperature rises (it does not fall)
3. Blue → red litmus shows an acid, not neutralisation; a pungent gas is not a sign of it

Trick: 'Neutral' means pH 7. The option with pH 7 is the right one.

Answer: (C) The pH of the solution becomes close to 7.

Concept: Each observation of α-scattering leads to one conclusion.

1. Most α-particles passed straight through, so the atom is mostly empty space
2. A few were deflected, so the positive charge is concentrated in a small region
3. Very few (about 1 in 12,000) bounced back, so the nucleus is very small and dense

Yaad rakhein: The nucleus is about 10⁵ times smaller than the atom (radius ~10⁻¹⁵ m vs ~10⁻¹⁰ m).

Answer: (B) the atom is mostly empty space

Concept: A complex tissue is made of more than one type of cell, all working together for one function.

1. Xylem: tracheids, vessels, xylem parenchyma, xylem fibres; carries water and minerals
2. Phloem: sieve tubes, companion cells, phloem parenchyma, phloem fibres; carries food
3. They are 'permanent' because their cells have lost the ability to divide

Yaad rakhein: Simple permanent tissues (parenchyma, collenchyma, sclerenchyma) have only one type of cell.

Answer: (C) They contain different types of cells working together for transport.

Concept: A molecule of an element contains only one kind of atom.

1. Examples: O₂, N₂, O₃, P₄, S₈ (same atoms bonded together)
2. Noble gases (He, Ne) are monoatomic, but not all elements are, so B is wrong
3. Different types of atoms make a compound, not an element (A is wrong)

Yaad rakhein: Atomicity: Ar = 1, O₂ = 2, O₃ = 3, P₄ = 4, S₈ = 8.

Answer: (C) A molecule of an element consists of only one type of atom bonded together.

Concept: 3R = Reduce, Reuse, Recycle.

1. Steel plates and bottles are used again and again, which is reuse
2. Fewer disposable cups thrown away means waste is reduced
3. Nothing is reprocessed, so this is not recycling

Yaad rakhein: Reuse is better than recycle because it needs no energy for reprocessing.

Answer: (D) Reduction and reuse of waste