RRB Technician Grade III 2024, 2025 PYQs

Concept: In a displacement reaction, a more reactive metal pushes out a less reactive metal from its salt solution.

1. Example: $\mathrm{F}\mathrm{e}+\mathrm{C}\mathrm{u}\mathrm{S}{\mathrm{O}}_4\to \mathrm{F}\mathrm{e}\mathrm{S}{\mathrm{O}}_4+\mathrm{C}\mathrm{u}$ – iron is above copper in the series.
2. $\mathrm{C}\mathrm{u}+\mathrm{F}\mathrm{e}\mathrm{S}{\mathrm{O}}_4$ → no reaction, as copper is below iron.
3. So the deciding factor is the relative position of the metals in the reactivity series.

Yaad rakhein: Higher in the reactivity series displaces lower – never the reverse.

Answer: (D) Position of the metals in the reactivity series

Concept: Covalent compounds form by sharing of electrons, usually between non-metals. Ionic compounds form by transfer of electrons from a metal to a non-metal.

1. $\mathrm{M}\mathrm{g}\mathrm{C}{\mathrm{l}}_2$, NaCl, MgO – metal + non-metal → ionic.
2. $\mathrm{C}{\mathrm{H}}_4$ – carbon shares its 4 valence electrons with 4 H atoms.
3. So $\mathrm{C}{\mathrm{H}}_4$ is covalent (4 single C–H bonds).

Trick: Metal + non-metal → ionic; non-metal + non-metal → covalent.

Answer: (D) ${\text{CH}}_4$

Concept: In multiple fission, the nucleus of a single-celled organism divides many times and the cell splits into many daughter cells at once.

1. Plasmodium (malaria parasite) reproduces by multiple fission.
2. Leishmania – binary fission (in a definite plane).
3. Yeast and Hydra – budding.

Yaad rakhein: Plasmodium → multiple; Amoeba, Leishmania → binary; Yeast, Hydra → budding.

Answer: (A) Plasmodium

Concept: A solution is a homogeneous mixture of two or more substances. The component present in larger amount is the solvent; the one in smaller amount is the solute.

1. (A) Wrong – a solution is homogeneous.
2. (B) Wrong – concentration can also be mass by volume, volume by volume, etc.
3. (D) Wrong – solute particles are too small to be separated by filtration.
4. (C) Correct – solute is present in a smaller amount than the solvent.

Yaad rakhein: Solution particles $<1\text{ nm}$ – they pass through filter paper and do not settle.

Answer: (C) The solute is present in a smaller amount than the solvent.

Concept: Rhizopus (bread mould) reproduces by spore formation. The thread-like hyphae form the vegetative body, not the reproductive part.

1. Sporangiophores – vertical hyphae carrying the sporangia (reproductive).
2. Sporangium – knob-like sac containing spores (reproductive).
3. Spores – develop into new Rhizopus (reproductive).
4. Hyphae – fine threads that spread over bread for nutrition, i.e. vegetative.

Yaad rakhein: Rhizopus: hyphae = body; blob on top (sporangium) = spore bag.

Answer: (D) Hyphae

Concept: The reaction between an acid and a base to give salt and water is called a neutralisation reaction.

1. General form: acid + base → salt + water.
2. Example: $\mathrm{N}\mathrm{a}\mathrm{O}\mathrm{H}+\mathrm{H}\mathrm{C}\mathrm{l}\to \mathrm{N}\mathrm{a}\mathrm{C}\mathrm{l}+{\mathrm{H}}_2\mathrm{O}$.
3. The ${\mathrm{H}}^{+}$ of the acid and $\mathrm{O}{\mathrm{H}}^{-}$ of the base combine to form ${\mathrm{H}}_2\mathrm{O}$.

Yaad rakhein: Antacid for acidity, baking soda for ant/bee sting, lime for acidic soil – all neutralisation.

Answer: (A) Neutralisation reaction

Concept: Work done $W=F\times s$. When force and displacement are in the same direction, the work is positive.

1. $F=1\text{ N}$, $s=1\text{ m}$ along the force.
2. $W=1\times 1=1\text{ J}$.
3. Same direction → positive, so $W=+1\text{ J}$.

Yaad rakhein: 1 joule = work done when a force of 1 N moves an object by 1 m along the force.

Answer: (C) $+1$ J

Concept: Tides (periodic rise and fall of sea water) are caused mainly by the gravitational pull of the moon on the earth's oceans.

1. The moon pulls the ocean water facing it more strongly, causing a bulge (high tide).
2. As the earth rotates, places pass through bulges, giving high and low tides.
3. Blue sky and rainbow are due to scattering/dispersion of light; thunderstorms are weather phenomena.

Yaad rakhein: Gravitation explains: tides, the moon orbiting the earth, planets orbiting the sun.

Answer: (C) Tides

Concept: For a spherical mirror, the distance between the pole (P) and the principal focus (F) is called the focal length $f$.

1. Radius of curvature $R$ = distance from pole to centre of curvature C.
2. Aperture = diameter of the reflecting surface.
3. Relation: $R=2f$, i.e. $f=\frac{R}{2}$.

Trick: PF = $f$, PC = $R$ = $2f$.

Answer: (B) focal length

Concept: A concave (diverging) lens always forms a virtual, erect and diminished image between F and the optical centre, on the same side as the object – wherever the object is placed.

1. Ray parallel to the axis diverges as if coming from F.
2. Ray through the optical centre O goes straight.
3. Their backward extensions meet between F and O → virtual, erect, smaller image.

Trick: Concave lens and convex mirror: image always virtual, erect, diminished.

Answer: (B) Virtual and diminished

Concept: Growth hormone is secreted by the pituitary gland and regulates growth and development of the body (all organs, bones, muscles).

1. Blood sugar is regulated by insulin (pancreas).
2. Menstrual cycle – by oestrogen/progesterone and pituitary sex-related hormones.
3. Metabolism – by thyroxin (thyroid).
4. Deficiency of growth hormone in childhood → dwarfism; excess → gigantism.

Yaad rakhein: Growth hormone – growth; thyroxin – metabolism; insulin – sugar.

Answer: (C) It stimulates growth in all organs.

Concept: In binary fission, a single-celled organism divides into two equal halves, each becoming a new individual.

1. Seen in Amoeba, Paramecium, bacteria, Leishmania.
2. Spore formation – Rhizopus; budding – Yeast, Hydra.
3. Regeneration – Planaria, Hydra (body pieces grow into new organisms).

Trick: "Bi" = two → binary fission gives two equal daughter cells.

Answer: (A) Binary fission

Concept: Metals differ in reactivity; arranging them in decreasing order gives the reactivity series: K > Na > Ca > Mg > Al > Zn > Fe > Pb > H > Cu > Hg > Ag > Au.

1. Silver is far less reactive than sodium – true.
2. Potassium (top) is more reactive than gold (bottom) – true.
3. Metals are not equally reactive – true; so "all metals are equally reactive" is incorrect.

Trick: Please Send Charlie's Monkeys And Zebras In Lead Hidden Cages Made of Silver and Gold (K, Na, Ca, Mg, Al, Zn, Fe, Pb, H, Cu, Hg, Ag, Au).

Answer: (A) All metals are equally reactive.

Concept: Organisms made of only one cell are called unicellular; that single cell performs all life functions.

1. Examples: Amoeba, Paramecium, Chlamydomonas, bacteria.
2. Organisms with many cells (humans, plants) are multicellular.
3. Unisexual refers to separate sexes, not cell number.

Yaad rakhein: Uni = one, multi = many.

Answer: (B) unicellular

Concept: Sexually transmitted diseases (STDs) are caused by bacteria or viruses and spread through sexual contact.

1. Bacterial: gonorrhoea and syphilis (treatable with antibiotics).
2. Viral: warts (HPV) and HIV-AIDS.
3. Only option (C) groups them correctly.

Trick: G-S = bacteria (Gonorrhoea, Syphilis); W-H = virus (Warts, HIV).

Answer: (C) Bacterial infections : Gonorrhoea and syphilis Viral infections : Warts and HIV-AIDS

Concept: Neurons are found in the nervous system – brain, spinal cord and nerves.

1. Brain and spinal cord form the central nervous system – made of neurons.
2. Nerves are bundles of axons of neurons.
3. An adipocyte is a fat-storing cell of adipose (connective) tissue – it has no neurons.

Yaad rakhein: Adipo = fat; adipocyte = fat cell, stores fat below skin and around organs.

Answer: (A) Adipocyte

Concept: Displacement is the shortest (straight-line) distance from the initial to the final position of an object, along with direction.

1. Distance = total path length (scalar).
2. Displacement = shortest distance between start and end (vector); it can be zero.
3. Speed and velocity are rates, and acceleration is rate of change of velocity.

Trick: Go around a circular track once – distance $=2\pi r$, displacement $=0$.

Answer: (C) displacement

Concept: Baking powder is a mixture of baking soda ($\mathrm{N}\mathrm{a}\mathrm{H}\mathrm{C}{\mathrm{O}}_3$) and a mild edible acid, tartaric acid.

1. On heating or mixing with water, $\mathrm{N}\mathrm{a}\mathrm{H}\mathrm{C}{\mathrm{O}}_3$ + ${\mathrm{H}}^{+}$ (from tartaric acid) → sodium salt + $\mathrm{C}{\mathrm{O}}_2$ + ${\mathrm{H}}_2\mathrm{O}$.
2. $\mathrm{C}{\mathrm{O}}_2$ makes bread and cakes soft and spongy.
3. Tartaric acid neutralises the bitter taste of sodium carbonate.

Yaad rakhein: Baking powder = baking soda + tartaric acid.

Answer: (B) Tartaric acid

Concept: When an object moves along a circular path with constant speed, its motion is called uniform circular motion.

1. Speed stays constant.
2. Direction of motion changes at every point (along the tangent).
3. So velocity changes → it is an accelerated motion, even though speed is uniform.

Yaad rakhein: Examples: the moon around the earth, a stone whirled on a string, tip of a clock's hand.

Answer: (B) uniform circular motion

Concept: Growth hormone is secreted by the pituitary gland, located at the base of the brain.

1. Pituitary – growth hormone; often called the master gland.
2. Thyroid – thyroxin (metabolism); adrenal – adrenaline (emergency).
3. Testes – testosterone (male characteristics).

Yaad rakhein: Too little growth hormone in childhood → dwarfism; too much → gigantism.

Answer: (A) Pituitary gland