RRB Technician Grade III 2024, 2025 PYQs

Concept: A parasitic plant depends on another living plant (host) for its food.

1. Cuscuta (amarbel) has no chlorophyll and grows on host plants, sucking nutrients through haustoria.
2. Cucumber, cabbage and cactus are green plants that photosynthesise – autotrophs.
3. Cactus is only adapted to deserts, not parasitic.

Yaad rakhein: Yellow, leafless, thread-like climber on trees = Cuscuta (amarbel).

Answer: (B) Cuscuta

Concept: Each change of state has a specific name.

1. Gas → solid directly: deposition (correct).
2. Solid → gas directly: sublimation (correct).
3. Liquid → gas below boiling point: evaporation (correct).
4. Gas → liquid is condensation, not sublimation – so this pair is wrong.

Yaad rakhein: Melting (S→L), Freezing (L→S), Evaporation (L→G), Condensation (G→L), Sublimation (S→G), Deposition (G→S).

Answer: (B) Gas to Liquid: Sublimation

Concept: Glucose first breaks into pyruvate in the cytoplasm; pyruvate then follows different pathways.

1. (i) Yeast (anaerobic): pyruvate → ethanol + $\mathrm{C}{\mathrm{O}}_2$ + energy. Correct.
2. (ii) Aerobic breakdown of pyruvate with oxygen occurs in the mitochondria, not chloroplast. Incorrect.
3. (iii) Muscles (lack of oxygen): pyruvate → lactic acid (causes cramps). Correct.

Yaad rakhein: Chloroplast = photosynthesis; mitochondria = aerobic respiration (powerhouse).

Answer: (C) Only (i) and (iii)

Concept: In many animals sex is fixed by genes/chromosomes, but in some it is not genetically predetermined.

1. Humans, dogs and pigeons – sex is decided by sex chromosomes.
2. In snails, individuals can change sex, so sex is not genetically fixed.
3. In some reptiles, egg incubation temperature decides the sex.

Yaad rakhein: NCERT: snail – sex can change; turtle/crocodile – temperature decides sex.

Answer: (D) Snail

Concept: Potential energy of a body at height $h$: $E_p=mgh$.

1. $m=8\text{ kg}$, $h=5\text{ m}$
2. $E_p=8\times g\times 5=40g\text{ J}$

Trick: Just multiply mass × height and keep $g$ as it is: $8\times 5=40$.

Answer: (C) 40g J

Concept: A heterogeneous mixture has non-uniform composition; its components can be seen as separate layers or particles.

1. Oil does not dissolve in water – it forms a separate layer → heterogeneous.
2. Ethanol in water, lemonade and tincture of iodine (iodine in alcohol) are uniform → homogeneous solutions.

Yaad rakhein: Oil + water = immiscible = heterogeneous; separated using a separating funnel.

Answer: (B) Mixture of oil in water

Concept: Electric power $P=VI$; combine it with Ohm's law $V=IR$.

1. Put $I=\frac{V}{R}$ in $P=VI$.
2. $P=V\times \frac{V}{R}=\frac{V^2}{R}$
3. Also $P=I^{2}R$.

Yaad rakhein: Three forms: $P=VI=I^{2}R=\frac{V^2}{R}$.

Answer: (A) $P=\frac{V^2}{R}$

Concept: Hot air is less dense (optically rarer) than cooler air above it, so its refractive index differs from place to place.

1. Above a fire or hot road, the refractive index keeps changing as the air moves.
2. Light from objects bends (refracts) by varying amounts.
3. So the apparent position of the object keeps fluctuating – it looks wavy.

Yaad rakhein: Wavy objects over fire, twinkling of stars, advance sunrise – all due to atmospheric refraction.

Answer: (A) Refraction of light

Concept: A colloid has particles of size about 1–1000 nm – between a true solution and a suspension.

1. It appears homogeneous but is actually a heterogeneous mixture.
2. Particles are too small to settle down when left undisturbed.
3. Particles scatter a beam of light – Tyndall effect.
4. So the statement 'colloid is a homogeneous mixture' is incorrect.

Yaad rakhein: Colloid: looks homogeneous, is heterogeneous, shows Tyndall effect, does not settle.

Answer: (A) Colloid is a homogeneous mixture.

Concept: Some plants reproduce vegetatively through their leaves.

1. In Bryophyllum, buds form in the notches along the leaf margin.
2. When the leaf falls on moist soil, these buds grow into new plants.
3. Grapes, rose and jasmine are usually propagated by stem cuttings or layering.

Yaad rakhein: Leaf buds in notches = Bryophyllum (patharchatta).

Answer: (B) Bryophyllum

Concept: Tiny air molecules scatter light of shorter wavelength much more than longer wavelength.

1. Blue light has a shorter wavelength than red, so it is scattered the most.
2. This scattered blue light reaches our eyes from all directions.
3. Hence the sky appears blue. Without atmosphere (e.g. in space) the sky looks dark.

Yaad rakhein: Blue sky, red sunrise/sunset, Tyndall effect – all due to scattering.

Answer: (A) Scattering of light

Concept: The fixed temperature at which a liquid turns into a solid on cooling is its freezing point.

1. For pure water, the freezing point is $0^{\circ }\text{C}$.
2. Melting point is for solid → liquid (on heating); for a pure substance both have the same value.
3. Boiling point is liquid → gas; condensation is gas → liquid.

Yaad rakhein: Cooling a liquid → freezing point; heating a solid → melting point.

Answer: (B) Freezing point

Concept: In myopia (near-sightedness) a person sees near objects clearly but not distant ones, because the image forms in front of the retina.

1. Cause: eye lens too converging (excessive curvature) or eyeball too long.
2. A concave (diverging) lens spreads the rays slightly before they enter the eye.
3. The image then forms exactly on the retina.

Trick: Myopia → Minus (concave) lens; Hypermetropia → convex (plus) lens.

Answer: (C) a concave lens of suitable power

Concept: A suspension is a heterogeneous mixture whose solid particles are large (above about 1000 nm).

1. Particles are big enough to be seen with the naked eye – statement true.
2. It is heterogeneous, not homogeneous.
3. Particles settle down when left undisturbed and can be separated by filtration.

Yaad rakhein: Suspension: visible particles, settles, filterable, scatters light (e.g. muddy water, chalk in water).

Answer: (A) The particles of a suspension can be seen by the naked eye.

Concept: Unicellular organisms reproduce by binary fission; the plane of division may be random or definite.

1. Leishmania (causes kala-azar) has a whip-like flagellum at one end.
2. Its binary fission occurs in a definite plane relative to the flagellum.
3. In Amoeba, fission can happen in any plane; Plasmodium shows multiple fission; yeast shows budding.

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

Answer: (D) Leishmania

Concept: In a parallel combination, every resistor is connected directly between the same two points P and Q.

1. So the potential difference across each resistor is the same → (A) correct.
2. Current divides: $I_1=\frac{V}{R_1}$, $I_2=\frac{V}{R_2}$.
3. If $R_1\ne R_2$, then $I_1\ne I_2$ → (B) incorrect. Total $I=I_1+I_2$.

Yaad rakhein: Series: same current; Parallel: same voltage.

Answer: (C) ‘A’ is correct and ‘B’ is incorrect.

Concept: Change of a liquid into vapour at any temperature below its boiling point is evaporation.

1. It is a surface phenomenon – only surface particles with enough energy escape.
2. Fusion = solid → liquid (melting); sublimation = solid → gas; deposition = gas → solid.
3. Evaporation increases with temperature, surface area and wind speed, and decreases with humidity.

Yaad rakhein: Evaporation causes cooling – e.g. sweating, earthen pot (matka) keeps water cool.

Answer: (C) evaporation

Concept: Newton's third law: to every action there is an equal and opposite reaction, acting on different bodies.

1. When the sailor jumps forward, he pushes the boat backward (action).
2. The boat pushes the sailor forward (reaction).
3. So the boat moves backward – a direct example of the third law (also momentum conservation).

Yaad rakhein: Recoil of gun, rocket launch, swimming, jumping from a boat – third law.

Answer: (A) Newton’s third law of motion

Concept: The Tyndall effect is the visible path of a light beam through a colloid, caused by scattering of light by its particles.

1. Colloidal particles are large enough to scatter light sideways.
2. The scattered light makes the beam's path visible.
3. Examples: sunlight beams through a dense forest canopy, light beam in a dusty room.

Yaad rakhein: True solution – no Tyndall effect; colloid & suspension – show it (scattering).

Answer: (A) Scattering of light

Concept: Refractive index $n=\frac{c}{v}$, so speed of light $v=\frac{c}{n}$ – lower $n$ means higher speed.

1. Values: water $1.33$, oil $1.46$, glycerine $1.5$, glass slab $1.65$.
2. Smallest $n=1.33$ (water).
3. So light travels fastest in water: $v=\frac{3\times {10}^8}{1.33}\approx 2.26\times {10}^8\text{ m/s}$.

Trick: Speed is inversely proportional to refractive index – pick the smallest $n$.

Answer: (C) water