RRB Technician Grade III 2024, 2025 PYQs

Concept: A soap molecule is the sodium/potassium salt of a long-chain fatty acid with two ends of different nature.

1. Ionic end ($-\mathrm{C}\mathrm{O}{\mathrm{O}}^{-}\mathrm{N}{\mathrm{a}}^{+}$) is hydrophilic — attracted to water.
2. Long hydrocarbon tail is hydrophobic — dissolves in oil/grease.
3. Molecules form micelles that trap oily dirt, which is rinsed away.

Yaad rakhein: Head loves water, tail hates water (loves oil) → micelle.

Answer: (B) Soap

Concept: The placenta is a disc-shaped tissue embedded in the uterine wall that links the embryo with the mother's blood.

1. Villi on the embryo side give a large surface area.
2. Glucose and oxygen pass from mother's blood to the embryo.
3. Wastes from the embryo pass into the mother's blood for removal.

Yaad rakhein: Oviduct → fertilisation site; Uterus → implantation; Placenta → nutrition of embryo.

Answer: (B) placenta

Concept: Testes are the male reproductive organs; they produce sperms and the hormone testosterone.

1. Testes lie outside the abdominal cavity in the scrotum, because sperm formation needs a temperature lower than body temperature – so (A) and (B) are wrong.
2. Sperms are formed in the testes, not in the seminal vesicles – (D) is wrong.
3. Testes secrete testosterone, which controls sperm formation and male secondary sexual characters – (C) is correct.

Yaad rakhein: Testes = sperm + testosterone; scrotum keeps them cooler than the body.

Answer: (C) Testes secrete testosterone hormone.

Concept: Endoplasmic reticulum (ER) is of two types: rough ER (RER) and smooth ER (SER).

1. RER has ribosomes attached to its surface, which give it a rough, granular look.
2. Ribosomes are the sites of protein synthesis, so RER makes proteins.
3. SER has no ribosomes and helps make fats (lipids).

Trick: Rough = Ribosomes (both start with R); Smooth = no ribosomes, makes lipids.

Answer: (B) ribosomes

Concept: Gravity always acts vertically downward, towards the centre of the Earth.

1. When a body is thrown upward, its motion (velocity) is upward.
2. Gravity acts downward, i.e. opposite to the motion, so the body slows down ($a=-g$).
3. At the highest point $v=0$, then the body falls back.

Trick: Going up → gravity opposes motion; coming down → gravity along motion.

Answer: (B) opposite to the direction of motion

Concept: Metals high in the reactivity series (K, Na, Ca, Mg, Al) cannot be reduced by carbon; they are obtained by electrolytic reduction.

1. Sodium is obtained by electrolysis of molten sodium chloride.
2. At cathode: $\mathrm{N}{\mathrm{a}}^{+}+{\mathrm{e}}^{-}\to \mathrm{N}\mathrm{a}$; at anode chlorine gas is released.
3. Zn and Pb are reduced by carbon; Ag is low in the series.

Yaad rakhein: Top of reactivity series (K, Na, Ca, Mg, Al) → electrolysis of molten salt.

Answer: (C) Na

Concept: Acids are sour, release ${\mathrm{H}}^{+}$ ions in water and have pH less than 7.

1. Acids turn blue litmus red – option (B).
2. Turning red litmus blue, pH greater than 7 and slippery (soapy) feel are properties of bases.
3. So only (B) is a property of acids.

Trick: Acid → Red (blue litmus turns red); Base → Blue.

Answer: (B) They turn blue litmus paper red.

Concept: Distance = total path length; displacement = shortest distance between initial and final positions.

1. Upward journey $=5\text{ m}$, downward journey $=5\text{ m}$.
2. Total distance $=5+5=10\text{ m}$.
3. The body returns to the starting point, so displacement $=0\text{ m}$.

Trick: Back to the starting point → displacement is always zero, distance is not.

Answer: (C) 0m, 10m

Concept: First law of refraction: the incident ray, the refracted ray and the normal at the point of incidence all lie in the same plane.

1. Second law (Snell's law): $\frac{\sin i}{\sin r}=\text{constant}$.
2. The blank refers to the ray that strikes the interface – the incident ray.
3. Reflected or emergent rays are not part of this law.

Yaad rakhein: Same-plane law has three members: incident ray, refracted ray, normal.

Answer: (C) Incident

Concept: Metal oxides are basic; they react with acids to form salt and water.

1. Copper oxide is CuO, in which copper is in +2 state.
2. $\mathrm{C}\mathrm{u}\mathrm{O}+2\mathrm{H}\mathrm{C}\mathrm{l}\to \mathrm{C}\mathrm{u}\mathrm{C}{\mathrm{l}}_2+{\mathrm{H}}_2\mathrm{O}$
3. $\mathrm{C}\mathrm{u}\mathrm{C}{\mathrm{l}}_2$ is copper(II) chloride; the solution turns blue-green.

Yaad rakhein: Metal oxide + acid → salt + water; blue-green colour = $\mathrm{C}\mathrm{u}\mathrm{C}{\mathrm{l}}_2$.

Answer: (D) Copper (II) chloride

Concept: Matter is made of extremely small particles.

1. Particles of matter have spaces between them.
2. They are continuously moving (they have kinetic energy).
3. They attract each other.
4. They are very small, not very large – so (C) is NOT a characteristic.

Yaad rakhein: Three properties: space between, constant motion, mutual attraction – and tiny size.

Answer: (C) They are very large in size.

Concept: For a concave mirror, an object placed between pole P and focus F gives an image behind the mirror.

1. A ray parallel to the axis reflects through F; a ray through C reflects back on itself.
2. The reflected rays diverge, so they meet only when extended behind the mirror.
3. Hence the image is virtual, erect and enlarged (used in shaving/make-up mirrors).

Yaad rakhein: Concave mirror gives a virtual, erect image only when the object is between P and F.

Answer: (C) Virtual and erect

Concept: Work is done when a force produces displacement in its direction.

1. $W=F\times s$ (force and displacement along the same direction).
2. In general, $W=Fs\cos \theta$.
3. SI unit: joule ($1\text{ J}=1\text{ N}\times 1\text{ m}$).

Trick: Work is a product, never a sum or difference: $W=F\times s$.

Answer: (A) force × displacement

Concept: The thyroid gland makes the hormone thyroxine, which needs iodine.

1. Thyroxine regulates carbohydrate, protein and fat metabolism.
2. Iodine deficiency → less thyroxine → swollen neck (goitre).
3. That is why iodised salt is recommended.

Yaad rakhein: Iodine → Thyroid → Thyroxine; deficiency → Goitre.

Answer: (A) Thyroid gland

Concept: In free fall, the body moves only under gravity with constant acceleration $g\approx 9.8\mathrm{m}{\mathrm{s}}^{-2}$.

1. Mass of the body does not change.
2. $G=6.67\times {10}^{-11}\mathrm{N}{\mathrm{m}}^2\mathrm{k}{\mathrm{g}}^{-2}$ is a universal constant.
3. Acceleration $g$ stays constant near the Earth.
4. Distance fallen keeps increasing: $s=\frac{1}{2}g{t}^2$ – it does NOT remain constant.

Trick: In free fall, velocity and distance change; $g$, $G$ and mass stay fixed.

Answer: (C) Distance

Concept: A decomposition reaction caused by heat is called thermal decomposition.

1. Limestone (calcium carbonate) on heating gives quicklime and carbon dioxide.
2. $\mathrm{C}\mathrm{a}\mathrm{C}{\mathrm{O}}_3\stackrel{\mathrm{\Delta }}{\to }\mathrm{C}\mathrm{a}\mathrm{O}+\mathrm{C}{\mathrm{O}}_2$
3. Only a carbonate can release $\mathrm{C}{\mathrm{O}}_2$, so the answer is calcium carbonate.

Trick: Need $\mathrm{C}{\mathrm{O}}_2$ as product → look for carbonate ($\mathrm{C}{\mathrm{O}}_3$).

Answer: (B) Calcium carbonate

Concept: Mechanical energy = kinetic energy + potential energy.

1. Kinetic energy: $E_k=\frac{1}{2}m{v}^2$ (due to motion).
2. Potential energy: $E_p=mgh$ (due to position or shape).
3. Light, heat and chemical energy are other forms, not parts of mechanical energy.

Yaad rakhein: Mechanical energy = KE + PE only.

Answer: (D) Potential energy

Concept: A solenoid is a long coil of many turns of insulated wire.

1. Inside the solenoid the field lines are parallel straight lines → field is uniform. (i) true.
2. Outside, the lines spread out, so the field is much weaker – not equal to inside. (ii) false.
3. The field pattern resembles that of a bar magnet, with N and S ends. (iii) true.

Yaad rakhein: Solenoid = bar magnet; uniform field inside (used to make electromagnets).

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

Concept: Fragmentation: the body breaks into pieces and each piece grows into a new individual.

1. Example: Spirogyra (a filamentous alga).
2. It is possible only when the body is simply organised, since every fragment can regrow the whole body.
3. Complex organisms have specialised organs and cannot regrow from fragments; unicellular organisms use fission instead.

Yaad rakhein: Fragmentation → simple multicellular (Spirogyra); fission → unicellular.

Answer: (A) only in simple body organised multicellular organisms

Concept: Photosynthesis: $6\mathrm{C}{\mathrm{O}}_2+12{\mathrm{H}}_2\mathrm{O}\to {\mathrm{C}}_6{\mathrm{H}}_{12}{\mathrm{O}}_6+6{\mathrm{O}}_2+6{\mathrm{H}}_2\mathrm{O}$ (in presence of sunlight and chlorophyll).

1. The glucose made is first used by the plant to provide energy (respiration).
2. The remaining carbohydrate is stored as starch – the internal energy reserve of plants.
3. Glycogen is the storage form in animals, not plants.

Yaad rakhein: Plants store starch; animals store glycogen.

Answer: (C) First, carbohydrates are utilised for energy production and the rest are stored in the form of starch.