RRB Technician Grade III 2024, 2025 PYQs

Concept: Robert Hooke discovered cells in 1665 while observing a thin slice of cork with a self-designed microscope.

1. The cork showed honeycomb-like compartments; he named them 'cells'.
2. He published this in his book 'Micrographia'.
3. Leeuwenhoek (1674) first saw free-living cells.

Yaad rakhein: 1665 – Hooke – cork – cell.

Answer: (A) 1665

Concept: After fertilisation, the parts of the flower change: ovule → seed, ovary → fruit, zygote → embryo.

1. The fertilised ovule develops a tough coat and becomes the seed.
2. The ovary ripens into the fruit.
3. Sepals, petals, stamens, stigma and style usually wither and fall.

Yaad rakhein: OVULE → SEED; OVARY → FRUIT.

Answer: (B) Ovule

Concept: Weak-stemmed climbers like pea have thin, thread-like tendrils that are sensitive to touch.

1. When a tendril touches a support, the part away from the support grows faster.
2. So the tendril coils around the fence or plant and the pea plant climbs up.
3. Sepals protect the bud, prickles give defence, roots absorb water – none help in climbing.

Yaad rakhein: Pea, cucumber, grapes, gourd climb using tendrils (touch-sensitive growth = thigmotropism).

Answer: (C) tendrils

Concept: A chemical reaction is recognised by observable signs: gas evolution, precipitate formation, change in state, colour change and temperature change.

1. (a) Gas: Zn + dil. ${\mathrm{H}}_2\mathrm{S}{\mathrm{O}}_4$ gives ${\mathrm{H}}_2$ bubbles.
2. (b) Precipitate: $\mathrm{P}\mathrm{b}(\mathrm{N}{\mathrm{O}}_3{)}_2$ + KI gives yellow $\mathrm{P}\mathrm{b}{\mathrm{I}}_2$.
3. (c) State change: burning candle wax; (d) colour change: iron nail in $\mathrm{C}\mathrm{u}\mathrm{S}{\mathrm{O}}_4$ solution.

Yaad rakhein: NCERT list – gas, precipitate, state, colour, temperature: all indicate a chemical reaction.

Answer: (A) All (a), (b), (c) and (d)

Concept: The thyroid gland secretes thyroxin, which controls carbohydrate, protein and fat metabolism.

1. Iodine is an essential part of the thyroxin molecule.
2. Iodine deficiency → less thyroxin → goitre (swollen neck).
3. Adrenaline – emergency; insulin – blood sugar; testosterone – male characters.

Trick: Iodine → Thyroid → Thyroxin → Metabolism; that is why iodised salt is advised.

Answer: (D) Thyroxin hormone

Concept: Energy due to motion is kinetic energy and energy due to position/height is potential energy.

1. $\text{KE}=\frac{1}{2}m{v}^2$ and $\text{PE}=mgh$.
2. Their sum is the total mechanical energy: $E=\text{KE}+\text{PE}$.
3. For a freely falling body (no air resistance), this total stays constant.

Yaad rakhein: Mechanical = Kinetic + Potential; thermal, chemical, electrical are other forms.

Answer: (A) Total mechanical energy

Concept: A phase transition is a change of matter from one state (solid, liquid, gas) to another.

1. Sublimation: solid → gas directly (camphor).
2. Vaporization: liquid → gas; Condensation: gas → liquid.
3. Emission (e.g. of light or gases) is not a change of state.

Yaad rakhein: State changes: melting, freezing, vaporization, condensation, sublimation, deposition.

Answer: (B) Emission

Concept: A solenoid is a long coil of many turns of insulated wire. The field produced by all turns adds up inside it.

1. Inside the solenoid the field is uniform (same everywhere).
2. A uniform field is shown by parallel straight lines, equally spaced.
3. Outside, lines curve from N to S like a bar magnet.

Yaad rakhein: Concentric circles = straight wire; parallel straight lines = inside a solenoid.

Answer: (C) parallel straight lines

Concept: Plants respond to environmental stimuli like light, gravity, water and chemicals by directional growth called tropism.

1. Phototropism: shoot grows towards light.
2. Geotropism: root grows downward with gravity, shoot upward.
3. So these triggers change the direction in which plant parts grow.

Yaad rakhein: Photo – light, Geo – gravity, Hydro – water, Chemo – chemicals.

Answer: (B) Change in the directions that plant parts grow in

Concept: Heat produced per second (power) in a resistor: $P=I^{2}R$.

1. $P=400\text{W}$ (400 J each second), $R=4\Omega$.
2. $I^2=\frac{P}{R}=\frac{400}{4}=100$.
3. $I=\sqrt{100}=10\text{A}$.

Trick: Check option: ${10}^2\times 4=400$ ✓ – just square each option and multiply by 4.

Answer: (D) 10 A

Concept: Temperature is a measure of the average kinetic energy of the particles of matter.

1. On heating, particles absorb energy and vibrate/move faster.
2. Faster motion means higher kinetic energy.
3. That is why heated solids melt and liquids evaporate faster.

Yaad rakhein: Temperature ↑ ⇒ KE of particles ↑ (and diffusion becomes faster).

Answer: (D) increases

Concept: In a double displacement reaction, two compounds exchange their ions to form two new compounds.

1. General form: $\mathrm{A}\mathrm{B}+\mathrm{C}\mathrm{D}\to \mathrm{A}\mathrm{D}+\mathrm{C}\mathrm{B}$.
2. Example: $\mathrm{N}{\mathrm{a}}_2\mathrm{S}{\mathrm{O}}_4+\mathrm{B}\mathrm{a}\mathrm{C}{\mathrm{l}}_2\to \mathrm{B}\mathrm{a}\mathrm{S}{\mathrm{O}}_4\downarrow +2\mathrm{N}\mathrm{a}\mathrm{C}\mathrm{l}$.
3. Decomposition breaks one compound; addition joins molecules – no ion exchange.

Trick: “Partners swap” = double displacement; often a precipitate forms.

Answer: (A) Double displacement reaction

Concept: Snell's law: for a given colour and pair of media, $\frac{\sin i}{\sin r}=\text{constant}=n_{21}$.

1. Going from rarer to denser medium, light bends towards the normal, so $r<i$.
2. Hence $\sin i>\sin r$, so $\frac{\sin i}{\sin r}>1$.
3. This constant is the refractive index of the denser medium w.r.t. the rarer one.

Yaad rakhein: Rarer → denser: bends towards normal, ratio $>1$; denser → rarer: ratio $<1$.

Answer: (B) a constant greater than 1

Concept: In Rhizopus (bread mould), the blob-like sporangia on hyphae contain many spores.

1. Spores are covered by thick walls that protect them until they reach a moist surface.
2. On a suitable surface each spore grows into a new Rhizopus.
3. This asexual method is called spore formation.

Yaad rakhein: Rhizopus – spores; Hydra/yeast – budding; Spirogyra – fragmentation; Planaria – regeneration.

Answer: (C) spore formation

Concept: Diffusion depends on how freely particles move and how much space lies between them.

1. In solids, particles are tightly packed and only vibrate in place.
2. In liquids, particles move freely and have more space between them.
3. So particles of another substance mix faster in liquids – diffusion rate is higher.

Yaad rakhein: Diffusion rate: gas > liquid > solid (more space and freedom → faster).

Answer: (B) in the liquid state, particles move freely and have greater space between each other

Concept: Atomicity = number of atoms in one molecule of an element.

1. Oxygen exists as ${\mathrm{O}}_2$ – two atoms, so diatomic.
2. Argon and helium are noble gases – monoatomic (Ar, He).
3. Phosphorus exists as ${\mathrm{P}}_4$ – tetra-atomic.

Yaad rakhein: Diatomic elements: ${\mathrm{H}}_2,{\mathrm{N}}_2,{\mathrm{O}}_2,{\mathrm{F}}_2,\mathrm{C}{\mathrm{l}}_2,\mathrm{B}{\mathrm{r}}_2,{\mathrm{I}}_2$.

Answer: (B) Oxygen

Concept: Force on mass $m$ near the earth: $F=\frac{GMm}{R^2}$, and $F=mg$.

1. Equate: $mg=\frac{GMm}{R^2}$.
2. $m$ cancels: $g=\frac{GM}{R^2}$.
3. $g$ depends only on the earth's mass and radius, not on the object's mass.

Trick: A feather and a coin fall together in vacuum – proof that $g$ is independent of $m$.

Answer: (A) independent of m

Concept: $R=\frac{V}{I}$, so unit of resistance = $\frac{\text{volt}}{\text{ampere}}=\Omega$ (ohm). Also $R=\rho \frac{l}{A}$.

1. $\rho =\frac{RA}{l}$ → unit $=\frac{\Omega \times {\text{m}}^2}{\text{m}}=\Omega \text{m}$.
2. (A) is wrong as resistivity is not ohm; (C) is wrong as resistivity is not volt/metre.
3. Only (D): resistance – ohm, resistivity – ohm metre.

Trick: Resistivity always carries an extra “metre”: ohm-metre.

Answer: (D) (a) Resistance - ohm (b) Resistivity - ohm metre

Concept: Meiosis is reduction division that forms gametes with half the chromosome number.

1. Meiosis I: 1 diploid cell → 2 cells.
2. Meiosis II: each of these divides again → 4 cells.
3. All four daughter cells are haploid.

Yaad rakhein: Mitosis → 2 identical cells; Meiosis → 4 haploid cells.

Answer: (A) Four

Concept: Heating lead nitrate is a thermal decomposition reaction.

1. $2\mathrm{P}\mathrm{b}(\mathrm{N}{\mathrm{O}}_3{)}_2\stackrel{\mathrm{\Delta }}{\to }2\mathrm{P}\mathrm{b}\mathrm{O}+4\mathrm{N}{\mathrm{O}}_2+{\mathrm{O}}_2$.
2. $\mathrm{N}{\mathrm{O}}_2$ (nitrogen dioxide) is a brown gas – the brown fumes seen.
3. $\mathrm{P}\mathrm{b}\mathrm{O}$ remains as yellow residue; ${\mathrm{O}}_2$ is colourless.

Yaad rakhein: Brown fumes = $\mathrm{N}{\mathrm{O}}_2$ (from heating nitrates like lead nitrate).

Answer: (C) Nitrogen dioxide gas