RRB Technician Grade III 2024, 2025 PYQs

Concept: Ernest Rutherford's alpha-particle scattering (gold foil) experiment (1911) revealed the nucleus.

1. Most alpha particles passed straight through → most of the atom is empty space.
2. A very few bounced back → a tiny, dense, positively charged centre exists – the nucleus.
3. Thomson discovered the electron, Chadwick the neutron, Bohr gave fixed orbits.

Yaad rakhein: Electron – Thomson; proton – Goldstein (canal rays); neutron – Chadwick; nucleus – Rutherford.

Answer: (B) E Rutherford

Concept: For uniform acceleration, the first equation of motion gives final velocity: $v=u+at$.

1. Starting from rest, so $u=0$.
2. $a=0.5{\text{m/s}}^2$, $t=20\text{s}$.
3. $v=0+0.5\times 20=10\text{m/s}$.

Trick: From rest, velocity is simply $a\times t$.

Answer: (D) 10 m/s

Concept: Air layers of different density bend (refract) light. Near the horizon, sunlight bends towards the Earth.

1. When the Sun is just below the horizon, refracted rays still reach us, so we see it about 2 minutes early.
2. Similarly the Sun stays visible about 2 minutes after it actually sets.
3. Plane mirror and curved mirror images are reflection; a rainbow is dispersion with internal reflection in drops.

Yaad rakhein: Atmospheric refraction: twinkling of stars, advance sunrise and delayed sunset (day longer by about 4 minutes).

Answer: (C) Advance sunrise and delayed sunset

Concept: A sol is a colloid in which the dispersed phase is a solid and the dispersion medium is a liquid.

1. Milk of magnesia: solid $\mathrm{M}\mathrm{g}(\mathrm{O}\mathrm{H}{)}_2$ dispersed in water → sol.
2. Foam (shaving cream): gas in liquid.
3. Rubber: gas in solid (solid foam); face cream: liquid in liquid (emulsion).

Yaad rakhein: Sol = solid in liquid (milk of magnesia, mud, paint); Gel = liquid in solid (jelly, cheese); Emulsion = liquid in liquid.

Answer: (B) Milk of magnesia

Concept: The endoplasmic reticulum (ER) is a network of membrane-bound tubes and sheets in the cytoplasm.

1. Its channels transport proteins and other materials between parts of the cell (and to the nucleus).
2. Its surface works as a factory floor: RER (with ribosomes) makes proteins, SER makes lipids.
3. Ribosomes only make proteins; mitochondria make energy; plastids store/photosynthesise.

Yaad rakhein: ER = cell's 'highway + workshop'; it also helps in membrane biogenesis.

Answer: (A) Endoplasmic reticulum

Concept: Ovaries secrete the female hormones oestrogen and progesterone.

1. Oestrogen develops female sex organs and secondary sexual characters.
2. Oestrogen and progesterone together regulate the menstrual cycle.
3. Pituitary is stimulated by hypothalamus; metabolism → thyroid; growth of all organs → growth hormone.

Yaad rakhein: Testes → testosterone; Ovaries → oestrogen/progesterone (menstrual cycle).

Answer: (D) Menstrual cycle

Concept: Growth hormone (GH) is secreted by the pituitary gland.

1. GH stimulates growth in all organs of the body.
2. Deficiency in childhood → dwarfism; excess → gigantism.
3. Metabolism → thyroxin; female sex organs → oestrogen; blood sugar → insulin.

Yaad rakhein: Pituitary = 'master gland'; its growth hormone controls overall body growth.

Answer: (D) It stimulates growth in all organs.

Concept: In electrolytic refining, impure metal is the anode, a thin strip of pure metal is the cathode, and a salt solution of the metal is the electrolyte.

1. On passing current, pure metal from the anode dissolves and deposits on the cathode.
2. Soluble impurities go into the solution.
3. Insoluble impurities settle below the anode — called anode mud.

Yaad rakhein: Impure → Anode, Pure → Cathode, waste below anode → anode mud.

Answer: (D) anode mud

Concept: A soap molecule has two ends: a long hydrocarbon tail and an ionic (carboxylate) head.

1. The ionic end is hydrophilic — it dissolves in (interacts with) water.
2. The hydrocarbon tail is hydrophobic — it dissolves in oil/grease.
3. In a micelle, tails point inward to trap oil and heads face the water.

Yaad rakhein: Hydro-PHILIC = water-loving (ionic head); hydro-PHOBIC = water-hating (oil-loving tail).

Answer: (C) Water

Concept: Rutherford's alpha-particle scattering experiment showed that the atom has a tiny, dense, positively charged centre — the nucleus.

1. Most alpha particles passed straight → most of the atom is empty space.
2. A very few bounced back → positive charge and mass are concentrated in a small region.
3. Electrons revolve around the nucleus and have negligible mass.

Yaad rakhein: Rutherford: nucleus holds nearly all the mass; size of nucleus is about ${10}^{-5}$ times that of the atom.

Answer: (B) In the nucleus

Concept: A helium atom has 2 protons and 2 electrons. Removing both electrons gives $\mathrm{H}{\mathrm{e}}^{2+}$ — a doubly-charged helium ion.

1. $\mathrm{H}{\mathrm{e}}^{2+}$ has 2 protons + 2 neutrons, mass 4 u, charge $+2$.
2. This is exactly an alpha particle (used by Rutherford).
3. Beta particles are electrons; gamma rays and X-rays are electromagnetic waves (no charge).

Yaad rakhein: Alpha = $\mathrm{H}{\mathrm{e}}^{2+}$ nucleus; Beta = electron; Gamma = EM radiation.

Answer: (C) Alpha particles

Concept: Food passes through the alimentary canal in a fixed sequence.

1. Mouth: chewing and saliva (starch digestion begins).
2. Oesophagus (food pipe): carries food by peristalsis.
3. Stomach → small intestine → large intestine → anus.

Yaad rakhein: Order: Mouth → Oesophagus → Stomach → Small intestine → Large intestine.

Answer: (B) Mouth - Oesophagus - Stomach

Concept: In uniform motion speed is constant, so distance is proportional to time: $d=v\times t$.

1. $v=\frac{25}{5}=5\text{m/s}$.
2. Distance in 3 s $=5\times 3=15\text{m}$.

Trick: Unitary method: 5 s → 25 m, so 3 s → $\frac{25}{5}\times 3=15\text{m}$.

Answer: (C) 15 m

Concept: A current-carrying solenoid behaves like a bar magnet; inside it the field lines are parallel and the field is strong and uniform.

1. More turns → stronger field: (A) correct.
2. Acts like a bar magnet with N and S ends: (B) correct.
3. Near the centre of a long solenoid field is nearly uniform: (C) correct.
4. Outside, field lines spread out, so the field is weak, not extremely large: (D) is INCORRECT.

Trick: Solenoid: strong & uniform INSIDE, weak OUTSIDE.

Answer: (D) The magnitude of the magnetic field outside but close to the solenoid is extremely large.

Concept: In a double displacement reaction two compounds exchange their ions: $AB+CD\to AD+CB$.

1. $2\mathrm{K}\mathrm{B}\mathrm{r}+\mathrm{B}\mathrm{a}{\mathrm{I}}_2\to 2\mathrm{K}\mathrm{I}+\mathrm{B}\mathrm{a}\mathrm{B}{\mathrm{r}}_2$.
2. ${\mathrm{K}}^{+}$ pairs with ${\mathrm{I}}^{-}$ and $\mathrm{B}{\mathrm{a}}^{2+}$ pairs with $\mathrm{B}{\mathrm{r}}^{-}$ — partners swapped.
3. A product separates out as a solid (precipitate), typical of such reactions.

Trick: Both sides have two compounds with swapped partners → double displacement.

Answer: (C) Double displacement reaction

Concept: Binary fission is division of a unicellular organism into two daughter cells.

1. In Amoeba, the splitting can occur in any plane (irregular binary fission).
2. In Leishmania, division occurs in a definite plane (longitudinal) because of its flagellum.
3. Plasmodium shows multiple fission; Hydra reproduces by budding (and is not a protozoan).

Yaad rakhein: Amoeba – any plane; Leishmania – definite plane; Plasmodium – multiple fission.

Answer: (B) Amoeba

Concept: Each step of a food chain is a trophic level.

1. 1st level: autotrophs/producers (green plants) fix solar energy.
2. 2nd level: herbivores = primary consumers.
3. 3rd level: small carnivores = secondary consumers; 4th: larger carnivores = tertiary consumers.
4. So options A, B, D misplace the organisms; C is correct.

Yaad rakhein: Producer → Primary (herbivore) → Secondary → Tertiary consumer; only about 10% energy passes to the next level.

Answer: (C) The autotrophs or the producers are at the first trophic level.

Concept: A chemical formula shows the elements in a substance and, through subscripts, how many atoms of each are present.

1. ${\mathrm{H}}_2\mathrm{O}$: subscript 2 → 2 hydrogen atoms, 1 oxygen atom.
2. $\mathrm{C}{\mathrm{O}}_2$: 1 carbon, 2 oxygen atoms.
3. Charge is written as a superscript (e.g. $\mathrm{C}{\mathrm{a}}^{2+}$), not a subscript.

Trick: Subscript (below) = atom count; superscript (above) = charge.

Answer: (D) The number of atoms of each element in a molecule

Concept: When a plant cell is placed in a hypertonic solution, water leaves the cell by osmosis.

1. The cell contents (protoplasm) shrink away from the cell wall.
2. This shrinking is called plasmolysis.
3. The reverse (cell swelling in hypotonic solution) gives turgidity / deplasmolysis.

Yaad rakhein: Plasmolysis = 'plasma moves away' from the wall; seen only in cells with a cell wall.

Answer: (C) Plasmolysis

Concept: Biotic components are living (plants, animals, microbes); abiotic components are non-living (soil, water, air, minerals, temperature).

1. A: Living organisms are biotic, not abiotic → wrong.
2. B: Soil is abiotic, not biotic → wrong.
3. C: Minerals are abiotic → correct.

Trick: 'Bio' = life: if it is alive it is biotic, otherwise abiotic.

Answer: (C) Only C