RRB Technician Grade III 2024, 2025 PYQs

Concept: Ethyne (acetylene) is an alkyne with general formula ${\mathrm{C}}_{\mathrm{n}}{\mathrm{H}}_{2\mathrm{n}-2}$ and a triple bond $\mathrm{H}-\mathrm{C}\equiv \mathrm{C}-\mathrm{H}$.

1. $n=2$: ${\mathrm{C}}_2{\mathrm{H}}_{2\times 2-2}={\mathrm{C}}_2{\mathrm{H}}_2$
2. ${\mathrm{C}}_2{\mathrm{H}}_6$ = ethane, ${\mathrm{C}}_2{\mathrm{H}}_4$ = ethene, $\mathrm{C}{\mathrm{H}}_4$ = methane.

Trick: Alkane ${\mathrm{C}}_{\mathrm{n}}{\mathrm{H}}_{2\mathrm{n}+2}$, alkene ${\mathrm{C}}_{\mathrm{n}}{\mathrm{H}}_{2\mathrm{n}}$, alkyne ${\mathrm{C}}_{\mathrm{n}}{\mathrm{H}}_{2\mathrm{n}-2}$.

Answer: (C) $C_2{H}_2$

Concept: A body at rest starts moving only when a net (unbalanced) force acts on it (Newton's first law).

1. Balanced forces cancel each other: net force $=0$, so the object stays at rest.
2. Upward and downward forces (weight and normal reaction) are vertical and balanced; they cannot produce horizontal motion.
3. To slide the object along the table, the applied push must exceed friction, giving a net (unbalanced) horizontal force.

Yaad rakhein: Motion changes only when $F_{\text{net}}\ne 0$ – i.e. an unbalanced force.

Answer: (A) unbalanced force

Concept: Solids and gases differ in how closely their particles are packed and how strongly they attract each other.

1. In solids, particles are very closely packed with strong forces of attraction, so they only vibrate in place.
2. In gases, particles are far apart, forces are negligible and they move freely at high speed.
3. Particles of a substance are the same in every state; gas particles have more (not less) kinetic energy.

Yaad rakhein: Packing order: solid > liquid > gas; freedom of movement: gas > liquid > solid.

Answer: (C) Solid particles are more closely packed than gas particles.

Concept: Plant hormones (phytohormones) each have a typical role; the one promoting cell division is cytokinin.

1. Cytokinins are present in higher concentration in areas of rapid cell division, such as fruits and seeds.
2. Auxin – cell elongation and bending of shoots towards light; Gibberellins – stem growth.
3. Abscisic acid inhibits growth and causes wilting of leaves (stress hormone).

Trick: Cytokinin = cytokinesis (cell division).

Answer: (C) Cytokinin

Concept: The testes are the primary male reproductive organs: they produce sperm and secrete the hormone testosterone.

1. Testes lie outside the abdominal cavity in the scrotum – so (A) is wrong.
2. Sperm need a temperature lower than normal body temperature; that is why the scrotum is outside – (D) is wrong.
3. Sperm are formed in the testes; seminal vesicles only add fluid – (B) is wrong.
4. Testosterone regulates sperm formation and male secondary sexual characters – (C) is correct.

Yaad rakhein: Testes: outside body, cooler, make sperm + testosterone.

Answer: (C) Testes secrete testosterone hormone.

Concept: Power is the rate of doing work: $P=\frac{W}{t}$, SI unit watt ($1\text{ W}=1\text{ J/s}$).

1. Work $W=50\text{ J}$, time $t=10\text{ s}$.
2. $P=\frac{50}{10}=5\text{ W}$.

Trick: Joules ÷ seconds = watts: $50÷10=5$.

Answer: (D) 5 W

Concept: CNG and LPG are common gaseous fuels used in vehicles and kitchens.

1. CNG = Compressed Natural Gas – mainly methane ($\mathrm{C}{\mathrm{H}}_4$), stored under high pressure; used in vehicles.
2. LPG = Liquefied Petroleum Gas – mainly butane (${\mathrm{C}}_4{\mathrm{H}}_{10}$) with propane, liquefied under pressure; used as cooking gas.
3. Words like 'Neutral' or 'Pressured' are distractors.

Yaad rakhein: CNG → Natural; LPG → Petroleum.

Answer: (B) Compressed Natural Gas and Liquefied Petroleum Gas

Concept: Glucose made in photosynthesis that is not used immediately is stored by plants as starch.

1. Leaves make glucose (${\mathrm{C}}_6{\mathrm{H}}_{12}{\mathrm{O}}_6$) during photosynthesis.
2. Extra glucose is converted to starch – the internal energy reserve of plants (test: iodine turns it blue-black).
3. Glycogen is the storage form in animals and fungi; cellulose forms the cell wall, not a food reserve.

Yaad rakhein: Plants store starch, animals store glycogen.

Answer: (C) starch

Concept: Our digestive enzymes can break down food substances like carbohydrates, proteins and fats, but not materials like coal or plastic.

1. Rice (carbohydrate) is digested by amylase – correct pair.
2. Protein is digested by pepsin and trypsin – correct pair.
3. Plastic is non-biodegradable; bacteria cannot break it down – correct pair.
4. Coal is not a food; our body cannot digest it – so 'Coal – digested in our body' is the INCORRECT pair.

Trick: Only food (carbohydrate, protein, fat) is digested; coal, plastic are not.

Answer: (D) Coal – digested in our body

Concept: Where cells face wear and tear, epithelial cells are arranged in many layers – stratified squamous epithelium.

1. Skin needs protection from wear and tear, so its epithelium is stratified squamous (NCERT example).
2. Kidney tubules have cuboidal epithelium; the lining of the stomach and intestine has columnar epithelium.
3. Hence, among the given parts, only the skin is made of stratified squamous epithelium.

Yaad rakhein: Stratified = many layers = protection (skin).

Answer: (B) Skin

Concept: In Bohr's model, the maximum number of electrons in the $n^{\text{th}}$ shell is $2n^2$.

1. Second energy level (L shell): $n=2$.
2. Maximum electrons $=2n^2=2\times 2^2=8$.
3. K = 2, L = 8, M = 18, N = 32.

Yaad rakhein: Shell capacity $2n^2$: 2, 8, 18, 32.

Answer: (A) 8

Concept: Liquids have a fixed volume but no fixed shape; their particles move more freely than those of solids.

1. Liquids flow and take the shape of the container – not rigid, no fixed shape: (A), (B) wrong.
2. Liquids do have a fixed volume – (C) wrong.
3. Particles of liquids have more space and kinetic energy than solids, so diffusion in liquids is faster than in solids – (D) correct.

Yaad rakhein: Diffusion rate: gas > liquid > solid.

Answer: (D) The rate of diffusion of liquids is higher than that of solids.

Concept: NCERT: the modes of reproduction used by different organisms depend on their body design.

1. Simple unicellular organisms (Amoeba) reproduce by fission.
2. Simple multicellular organisms like Hydra use budding or regeneration; Planaria regenerates from pieces.
3. Complex organisms with specialised organs use sexual reproduction. Thus body design decides the mode.

Trick: Simple body → simple method (fission); complex body → sexual reproduction.

Answer: (D) body design of the organisms

Concept: Evaporation causes cooling; the faster sweat evaporates, the cooler we feel.

1. In summer we sweat more.
2. Cotton is a good absorber of water; it soaks up sweat.
3. It spreads the sweat and exposes it to air, so it evaporates quickly, absorbing latent heat from the body and cooling it.

Yaad rakhein: Cotton = absorb + evaporate = cooling.

Answer: (C) cotton is a good absorber of water and exposes sweat to atmosphere for evaporation

Concept: A mixture is a physical combination; a compound is a chemical combination in a fixed ratio.

1. Statement 1: a mixture has variable composition (e.g. sugar solution of any strength) – correct.
2. Statement 2: a compound always has fixed composition (water: H and O in mass ratio $1:8$) – correct.
3. Statement 3: a mixture shows properties of its constituents (iron in iron–sulphur mixture is still magnetic) – correct.

Yaad rakhein: Mixture: variable, keeps properties. Compound: fixed, new properties.

Answer: (B) 1, 2 and 3

Concept: The kidney's basic filtration unit is the nephron; each kidney has a large number of them packed closely.

1. Each nephron has a cup-shaped Bowman's capsule enclosing a capillary cluster (glomerulus) and a long tubule.
2. The glomerulus is only a part of the nephron, not the whole unit.
3. Neurone is the unit of the nervous system.

Yaad rakhein: Kidney → nephron; nerve → neurone.

Answer: (B) Nephron

Concept: Blood has a fluid medium (plasma) in which cells are suspended.

1. Plasma transports food, carbon dioxide and nitrogenous wastes in dissolved form.
2. RBCs carry oxygen (haemoglobin); platelets help in clotting.
3. Lymph carries digested fat and drains excess tissue fluid.

Yaad rakhein: Dissolved transport → plasma; oxygen → RBC.

Answer: (B) Plasma

Concept: In a double displacement reaction, two compounds exchange ions: $\mathrm{A}\mathrm{B}+\mathrm{C}\mathrm{D}\to \mathrm{A}\mathrm{D}+\mathrm{C}\mathrm{B}$ (often a precipitate forms).

1. (1) $\mathrm{C}+{\mathrm{O}}_2\to \mathrm{C}{\mathrm{O}}_2$: combination.
2. (2) $\mathrm{N}{\mathrm{a}}_2\mathrm{S}{\mathrm{O}}_4+\mathrm{B}\mathrm{a}\mathrm{C}{\mathrm{l}}_2\to \mathrm{B}\mathrm{a}\mathrm{S}{\mathrm{O}}_4\downarrow +2\mathrm{N}\mathrm{a}\mathrm{C}\mathrm{l}$: ions exchanged – double displacement.
3. (3) $\mathrm{P}\mathrm{b}+\mathrm{C}\mathrm{u}\mathrm{C}{\mathrm{l}}_2\to \mathrm{P}\mathrm{b}\mathrm{C}{\mathrm{l}}_2+\mathrm{C}\mathrm{u}$: single displacement.
4. (4) $\mathrm{C}\mathrm{a}\mathrm{C}{\mathrm{O}}_3\to \mathrm{C}\mathrm{a}\mathrm{O}+\mathrm{C}{\mathrm{O}}_2$: decomposition.

Trick: Two compounds in, two compounds out with partner swap = double displacement.

Answer: (C) Only 2

Concept: A nerve is a bundle of many nerve fibres (axons) held together by connective tissue.

1. Nerve cells (neurons) have long fibres.
2. Many such fibres are bound together by connective tissue to form a nerve.
3. Vascular and meristematic tissues are plant tissues; epithelial tissue covers surfaces.

Yaad rakhein: Connective tissue binds and joins – bones, ligaments, and nerve fibres.

Answer: (B) Connective tissue

Concept: Pollination is the transfer of pollen from the anther (stamen) to the stigma.

1. If pollen reaches the stigma of the same flower – self-pollination.
2. If it reaches the stigma of another flower – cross-pollination (by wind, water, insects).
3. Fertilisation is the later fusion of male and female gametes.

Yaad rakhein: Same flower = self; different flower = cross.

Answer: (B) self-pollination