RRB Technician Grade III 2024, 2025 PYQs

Concept: Liquids have particles closer than gases but free to slide past each other.

1. Fixed volume: particles are held by fairly strong attraction.
2. No fixed shape: liquid takes the shape of its container.
3. Liquids are almost incompressible and not hard; fixed shape and volume belong to solids; high compressibility to gases.

Yaad rakhein: Solid: fixed shape + volume; Liquid: fixed volume only; Gas: neither.

Answer: (C) It has fixed volume but not fixed shape.

Concept: Acceleration is the rate of change of velocity: $a=\frac{v-u}{t}$.

1. Velocity not changing with time → uniform motion (A is wrong).
2. Change in velocity per unit time → acceleration (B is correct).
3. Free fall → uniform acceleration $g$ (C wrong); velocity varying with time → non-uniform motion (D wrong).

Yaad rakhein: Free fall is the classic example of uniform acceleration ($g\approx 9.8{\text{m/s}}^2$).

Answer: (B) Change in velocity per unit time - Acceleration

Concept: A suspension is a heterogeneous mixture whose solid particles are visible to the naked eye and settle down on standing.

1. Chalk powder in water: particles visible and settle → suspension.
2. Sugar in water → true solution.
3. Few drops of milk in water → colloid; oil in water → emulsion (colloid type).

Yaad rakhein: Suspension examples: chalk/sand/muddy water, flour in water; particle size more than 100 nm.

Answer: (C) Chalk powder in water

Concept: In electrolytic refining, metal ions move from the impure anode through the electrolyte and deposit as pure metal on the cathode.

1. Anode: thick block of impure metal.
2. Cathode: thin strip of pure metal.
3. Electrolyte: solution of a salt of the same metal (e.g. acidified $\mathrm{C}\mathrm{u}\mathrm{S}{\mathrm{O}}_4$ for copper).

Yaad rakhein: Pure metal collects on the pure-metal cathode; impurities fall as anode mud.

Answer: (D) pure metal

Concept: Olfactory indicators change their smell in acidic or basic medium.

1. Vanilla essence, onion and clove oil are olfactory indicators.
2. Vanilla smell disappears in a base but remains in an acid.
3. Phenolphthalein, litmus and methyl orange are visual (colour-change) indicators.

Yaad rakhein: Olfactory = smell: vanilla, onion, clove.

Answer: (B) Vanilla essence

Concept: A triangular prism has two triangular bases and three rectangular lateral faces.

1. Light enters through one lateral face and leaves through another.
2. The angle between these two refracting lateral faces is the angle of prism ($A$).
3. Angle of deviation is the angle between incident ray and emergent ray.

Yaad rakhein: For a prism: $A+\delta =i+e$.

Answer: (D) Angle of prism

Concept: Colloidal particles are too small to be stopped by filter paper and do not settle on their own.

1. Centrifugation spins the mixture very fast.
2. The denser particles are forced to the bottom and separate out.
3. Example: separating cream from milk; blood cells from plasma.

Trick: Filter paper fails for colloids → spin them out (centrifuge).

Answer: (D) Centrifugation

Concept: Newton's first law: a body tends to remain in its state of rest or motion (inertia).

1. When the bus starts suddenly, our feet in contact with the floor move forward with the bus.
2. The upper body, due to inertia of rest, tends to stay where it was.
3. So we fall backwards. (On sudden braking we fall forward — inertia of motion.)

Trick: Bus starts → fall backward; bus stops → fall forward.

Answer: (A) backwards

Concept: Speed = distance ÷ time. In one round of a circle the distance covered is its circumference $2\pi r$.

1. Distance in one round $=2\pi r$.
2. Time for one round $=t$.
3. $v=\frac{2\pi r}{t}$.

Yaad rakhein: $\pi r^2$ is area, not distance — reject such options at once.

Answer: (A) $v=2\pi r/t$

Concept: Evaporation needs latent heat; the liquid takes this heat from its surroundings, which cool down.

1. Sweat on the skin evaporates.
2. The heat needed for evaporation is absorbed from the body surface.
3. So the body loses heat and feels cool.

Yaad rakhein: Same reason: earthen pot cools water; we wear cotton clothes in summer.

Answer: (D) Sweating causes rapid evaporation, which absorbs heat from the body surface and cools the body.

Concept: Displacement is the shortest straight-line distance from initial to final position (with direction); distance is the total path length.

1. A → B: 15 m right; B → A: 15 m left.
2. Final position = initial position A.
3. Displacement $=0\text{m}$ (distance $=15+15=30\text{m}$).

Trick: Back to the starting point → displacement is always zero.

Answer: (A) 0 m

Concept: If velocity changes by equal amounts in equal time intervals, acceleration is uniform; otherwise it is non-uniform.

1. The speed increases, so the car is accelerating (not uniform speed/velocity).
2. Increases are unequal in equal intervals.
3. Hence the acceleration is non-uniform.

Trick: Equal change in equal time → uniform; unequal change → non-uniform.

Answer: (A) non-uniform acceleration

Concept: Fertilisation is the fusion of the male gamete with the female gamete.

1. The male gamete is formed in the pollen grain (from the stamen).
2. The female gamete (egg) lies in the ovule inside the ovary (pistil).
3. Sepals, petals and thalamus are non-essential (accessory) parts.

Yaad rakhein: Essential whorls: stamen and pistil; accessory whorls: sepals and petals.

Answer: (A) Pollen grain and ovule

Concept: Mitochondria carry out cellular respiration and release energy in the form of ATP.

1. ATP is the 'energy currency' of the cell, so mitochondria are called the powerhouse of the cell.
2. They have their own DNA and ribosomes.
3. Lysosomes = suicide bags; plastids = kitchen (chloroplast); vacuoles = storage sacs.

Yaad rakhein: Powerhouse → mitochondria; suicide bag → lysosome; kitchen → chloroplast.

Answer: (B) Mitochondria

Concept: The ozone layer in the stratosphere absorbs harmful UV radiation from the Sun.

1. In the 1980s ozone levels fell sharply.
2. The main cause: synthetic chlorofluorocarbons (CFCs) used in refrigerators, ACs and fire extinguishers.
3. UV breaks CFCs, releasing chlorine atoms that destroy ozone molecules.

Yaad rakhein: Montreal Protocol (1987) agreed to phase out CFCs; ozone is ${\mathrm{O}}_3$.

Answer: (D) Chlorofluorocarbons

Concept: An object in a liquid experiences upward buoyant force (upthrust) and downward force of gravity (its weight).

1. If upthrust $>$ weight → net force is upward → the object floats.
2. If upthrust $<$ weight → the object sinks.
3. Here upthrust is greater, so the iron rod floats on the surface.

Trick: Compare the two forces: upthrust wins → float; weight wins → sink.

Answer: (A) The iron rod would float on water surface.

Concept: The closeness of field lines shows field strength and their direction shows field direction.

1. Uniform field = same strength and same direction everywhere.
2. Same direction → lines are parallel and straight.
3. Same strength → lines are equally spaced (equidistant).

Yaad rakhein: Concentric circles → field of a straight current-carrying wire; parallel lines → inside a solenoid (uniform).

Answer: (C) parallel and equidistant straight lines

Concept: Simple permanent tissues in plants: parenchyma, collenchyma and sclerenchyma.

1. Collenchyma cells are living, elongated and irregularly thickened at the corners.
2. This gives flexibility and mechanical support, so tendrils and climber stems bend without breaking.
3. Found in leaf stalks below the epidermis.

Yaad rakhein: Chlorenchyma → photosynthesis; aerenchyma → buoyancy in aquatic plants; sclerenchyma → hardness (husk of coconut).

Answer: (B) Collenchyma

Concept: Connective tissue is an animal tissue whose cells lie in a matrix; it connects and supports body parts.

1. Blood (fluid matrix plasma), bone and cartilage are animal connective tissues.
2. Tracheid is a plant tissue — an element of xylem (complex permanent tissue).
3. So tracheid is the odd one out.

Trick: Spot the plant word: tracheid, vessel, sieve tube → plant tissues.

Answer: (B) tracheid

Concept: The hypothalamus links the nervous system with the endocrine system and controls the pituitary.

1. When growth hormone level is low, the hypothalamus releases growth hormone releasing factor.
2. This factor stimulates the pituitary gland.
3. The pituitary then releases growth hormone.

Yaad rakhein: Hypothalamus → releasing factors → pituitary → hormones (feedback control).

Answer: (B) Hypothalamus