RRB Technician Grade III 2024, 2025 PYQs

Concept: Vascular (conducting) tissue – xylem and phloem – is a distinctive feature of complex plants and made their survival on land possible.

1. Xylem carries water and minerals from roots upward.
2. Phloem carries food from leaves to other parts.
3. This allows plants to grow tall and live away from water.
4. Connective and epithelial tissues are animal tissues.

Yaad rakhein: Xylem → water (one way, up); phloem → food (both ways).

Answer: (A) Vascular tissue

Concept: Hard water contains $\mathrm{C}{\mathrm{a}}^{2+}$ and $\mathrm{M}{\mathrm{g}}^{2+}$ ions, which react with soap.

1. Soap (sodium salt of fatty acid) reacts with these ions.
2. An insoluble precipitate called scum forms.
3. Much soap is wasted and little lather forms – so (B) is wrong.

Yaad rakhein: Detergents work well even in hard water because they do not form scum.

Answer: (C) Formation of soap scum due to the reaction with calcium and magnesium ions.

Concept: Sublimation is the direct change of a solid into vapour (gas) without passing through the liquid state.

1. Examples: camphor, naphthalene, ammonium chloride, iodine, dry ice.
2. Deposition is the reverse: gas → solid directly.
3. Fusion: solid → liquid; solidification: liquid → solid.

Yaad rakhein: Solid → gas = sublimation; gas → solid = deposition.

Answer: (B) Sublimation

Concept: Vegetative propagation is the formation of new plants from vegetative parts – root, stem and leaves.

1. Stem: potato tuber, ginger, sugarcane.
2. Root: sweet potato, dahlia.
3. Leaves: Bryophyllum (buds on leaf margin).
4. The flower is a reproductive part (sexual reproduction), not vegetative.

Yaad rakhein: Vegetative = non-flower parts; flower = sexual reproduction.

Answer: (C) Flower

Concept: In a non-dividing nucleus, DNA and protein exist as a thread-like network called chromatin.

1. When the cell is about to divide, chromatin condenses.
2. It becomes compact rod-shaped structures called chromosomes.
3. Chromosomes carry genes and pass them to daughter cells.

Yaad rakhein: Chromatin (thread, interphase) → chromosomes (rods, division).

Answer: (A) Chromosomes

Concept: Carbon monoxide combines with hydrogen (catalyst, high pressure) to form methanol – a combination reaction.

1. $\mathrm{C}\mathrm{O}(\mathrm{g})+2{\mathrm{H}}_2(\mathrm{g})\to \mathrm{C}{\mathrm{H}}_3\mathrm{O}\mathrm{H}(\mathrm{l})$
2. Atoms: C = 1, O = 1, H = 4 on both sides – balanced.
3. Other options contain O or extra products that cannot come only from CO and H₂ without balance.

Yaad rakhein: Methanol is made industrially from 'syn gas' (CO + H₂).

Answer: (C) ${\text{CH}}_3\text{OH(I)}$

Concept: Regeneration is the ability of an organism to regrow lost or cut body parts (e.g. Planaria, Hydra).

1. Reproduction is the normal process of producing new individuals.
2. Regeneration is carried out by specialised cells and is not the usual way most organisms reproduce.
3. So regeneration is not the same as reproduction; many organisms can regenerate, so (C) is wrong.

Yaad rakhein: Planaria cut into pieces – each piece grows into a complete Planaria.

Answer: (B) Regeneration is not the same as reproduction.

Concept: The principal axis is the straight line passing through the pole (P) and the centre of curvature (C) of a spherical mirror.

1. Any radius (line from C) meets the mirror surface at right angles.
2. The principal axis is the radius through P.
3. So it is normal to the mirror at its pole, making ${90}^{\circ }$ with the surface there.

Yaad rakhein: P, F and C all lie on the principal axis; F is midway between P and C.

Answer: (B) It is normal to the mirror at its pole.

Concept: Colloidal particles are too small to be stopped by filter paper and do not settle on standing; they are separated by centrifugation.

1. In a centrifuge, the mixture is spun very fast.
2. Denser particles are forced to the bottom; lighter liquid stays on top.
3. Examples: separating cream from milk, blood tests, butter making.

Yaad rakhein: Filtration → suspension; sublimation → camphor/NH₄Cl; centrifugation → colloid (cream from milk).

Answer: (B) Centrifugation technique

Concept: Ores mined from the earth contain large amounts of impurities such as soil, sand and rock; these impurities are called gangue.

1. Gangue is removed first (concentration/enrichment of ore).
2. Roasting: heating sulphide ore in excess air.
3. Calcination: heating carbonate ore in limited air.
4. Anode mud: impurities settling below the anode in electrolytic refining.

Yaad rakhein: Gangue + flux → slag.

Answer: (A) Gangue

Concept: In plants, xylem carries water and minerals absorbed by roots; phloem carries food (translocation).

1. a. Phloem absorbs water and minerals from soil – incorrect (this is xylem's role with root hairs).
2. b. Root hairs increase surface area for absorption – correct.
3. c. Vascular tissue transports water and nutrients – correct.
4. d. Xylem forms a continuous channel from roots to leaves – correct.

Yaad rakhein: Xylem = water up; phloem = food (sugar) everywhere.

Answer: (C) Only a

Concept: Almost the entire mass of an atom lies in its nucleus, which contains protons and neutrons (together called nucleons).

1. Mass of proton ≈ neutron ≈ $1\text{u}$.
2. Electron mass is about $\frac{1}{1836}$ of a proton – negligible.
3. Mass number A = protons + neutrons = number of nucleons.

Trick: Example: ${}_{11}^{23}\mathrm{N}\mathrm{a}$ has 23 nucleons → mass ≈ $23\text{u}$.

Answer: (C) nucleons

Concept: Some organelles are present only in plant cells, while others are common to both plant and animal cells.

1. Mitochondria and Golgi apparatus – present in both.
2. Lysosomes – mainly in animal cells.
3. Plastids and cell wall – only in plant cells.
4. Large central vacuole – characteristic of plant cells (animal cells have small or no vacuoles).

Yaad rakhein: Plant-only trio: cell wall, plastids, large vacuole.

Answer: (B) b, d and e

Concept: Power of a lens is the reciprocal of its focal length: $P=\frac{1}{f}$ (f in metre, P in dioptre).

1. So $P\propto \frac{1}{f}$ – inversely proportional to focal length.
2. Not $\frac{1}{f^2}$, so (A) is wrong.
3. Example: $f=0.25\text{m}\Rightarrow P=4\text{D}$.

Trick: Halve the focal length → power doubles.

Answer: (B) Power is inversely proportional to focal length.

Concept: Magnetic field lines show the direction and strength of a magnetic field.

1. Closer lines → stronger field – (A) true.
2. Lines are closed curves (N to S outside, S to N inside) – (C) true.
3. Direction = where the compass north pole points – (D) true.
4. Parallel, equidistant lines show a uniform field (e.g. inside a solenoid), not zero field – (B) false.

Yaad rakhein: Two field lines never intersect.

Answer: (B) If magnetic field lines are parallel and equidistant, they represent zero field strength.

Concept: Chlorine occurs as ${}^{35}\mathrm{C}\mathrm{l}$ and ${}^{37}\mathrm{C}\mathrm{l}$ in the ratio $3:1$, which explains its fractional atomic mass $35.5\text{u}$.

1. Average mass $=\frac{35\times 3+37\times 1}{4}$
2. $=\frac{105+37}{4}=\frac{142}{4}=35.5\text{u}$
3. This matches the known atomic mass of chlorine.

Trick: Check any ratio with the average: only $3:1$ gives $35.5$.

Answer: (A) 3 : 1

Concept: Non-biodegradable substances (plastics, DDT, glass) cannot be broken down by microbes.

1. A. Not broken down by biological processes – correct.
2. B. They persist for a long time, not a short period – incorrect.
3. C. They harm organisms and can accumulate in food chains (biomagnification) – correct.

Yaad rakhein: DDT concentration increases at each trophic level – biological magnification.

Answer: (D) Both A and C

Concept: Endoplasmic reticulum (ER) is a network of membrane-bound tubes and sheets in the cell.

1. Rough ER (RER): has ribosomes on its surface; makes proteins.
2. Smooth ER (SER): no ribosomes; makes lipids and helps detoxify poisons and drugs.
3. So there are two types.

Yaad rakhein: SER also helps in making membrane lipids (membrane biogenesis).

Answer: (D) Two

Concept: For a concave mirror, rays parallel to the principal axis, after reflection, converge at a single point on the axis – the principal focus (F).

1. Parallel rays strike the mirror (see figure).
2. After reflection all of them pass through F.
3. F lies midway between P and C: $f=\frac{R}{2}$.

Yaad rakhein: Concave mirror: real focus (rays actually meet); convex mirror: rays only appear to come from F.

Answer: (A) at the principal focus

Concept: Magnification $m=\frac{h^{\prime }}{h}=\frac{\text{image height}}{\text{object height}}$.

1. $h=30\text{cm},h^{\prime }=10\text{cm}$
2. $m=\frac{10}{30}=\frac{1}{3}$
3. A concave lens always forms a virtual, erect, diminished image, so m is positive and less than 1.

Trick: Concave lens → $0<m<1$; only $\frac{1}{3}$ fits among the options.

Answer: (B) $1/3$