RRB Technician Grade III 2024, 2025 PYQs

Concept: Osmosis is the movement of solvent (water) through a semipermeable membrane from a dilute to a concentrated solution.

1. The membrane lets water pass but not sugar
2. Water moves into the concentrated side, so its level rises and the other side falls
3. Diffusion is wrong because sugar cannot cross a semipermeable membrane

Trick: Semipermeable membrane + change in levels = osmosis. Water moves toward more solute.

Answer: (D) Osmosis – because solvent molecules move from the dilute solution to the concentrated solution through the semipermeable membrane

Concept: In a hypotonic medium water enters the cell by osmosis and the cell swells.

1. The rigid cellulose cell wall resists the swelling, so the cell becomes turgid but does not burst
2. Animal cells have no cell wall, so they can burst (e.g. RBCs in water)

Yaad rakhein: The pressure of the cell contents against the wall is called turgor pressure; it keeps soft plant parts firm.

Answer: (C) Cell wall made of cellulose

Concept: At maximum height all the initial KE has changed into PE.

1. $KE=\frac{1}{2}m{v}^2=\frac{1}{2}\times 10\times {10}^2=500$ J
2. PE at the top = 500 J (check: $h=\frac{v^2}{2g}=5$ m, so $mgh=10\times 10\times 5=500$ J)

Trick: PE at the top = KE at launch, so you do not need to find the height.

Answer: (A) 500 J

Concept: To convert km/h to m/s, multiply by $\frac{5}{18}$.

1. $40\times \frac{5}{18}=\frac{200}{18}$
2. $=11.11$ m/s (the 10 minutes is extra data)

Trick: Divide by 3.6: $40÷3.6\approx 11.1$.

Answer: (D) 11.11 m/s

Concept: The atomic number (number of protons) decides which element an atom is.

1. Same atomic number but different mass numbers means isotopes of the same element (e.g. ${}^{12}\text{C}$, ${}^{14}\text{C}$)
2. Different atomic numbers always mean different elements (isobars, isotones)

Yaad rakhein: Isotopes: same Z. Isobars: same A (e.g. ${}^{40}\text{Ca}$, ${}^{40}\text{Ar}$). Isotones: same number of neutrons.

Answer: (D) Same atomic number, different mass numbers

Concept: Ions are held by strong electrostatic forces in a rigid crystal lattice.

1. Strong attraction gives a high melting point (A ✓); the rigid lattice makes them brittle (D ✓)
2. They dissolve in water but not in non-polar solvents like kerosene (B ✗)
3. They conduct only when molten or in solution, not as solids, since the ions cannot move (C ✗)

Trick: Rule out B and C (both are false), which leaves only A and D.

Answer: (D) Only (A) and (D)

Concept: Dendrite → cell body → axon → nerve ending.

1. Dendrites receive the signal; the axon carries the electrical impulse away from the cell body
2. At the axon ending, chemicals are released across the synapse to the next neuron or to a muscle/gland

Yaad rakhein: The longest cell in the human body is the nerve cell (neuron).

Answer: (C) Transmit electrical impulses to other neurons or target organs.

Concept: Acid + carbonate/hydrogen carbonate → salt + CO₂ + water.

1. ${\text{NaHCO}}_3+\text{HCl}\to \text{NaCl}+{\text{H}}_2\text{O}+{\text{CO}}_2\uparrow$
2. CO₂ turns lime water milky

Trick: 'Carbonate' means CO₂ will be formed. Acid + metal gives H₂; acid + carbonate gives CO₂.

Answer: (B) Salt, carbon dioxide and water

Concept: Smooth muscle is involuntary and found in the walls of internal organs.

1. Peristalsis (movement of food in the alimentary canal) is done by smooth muscle
2. Walking and waving use striated (voluntary) muscle; the heart has cardiac muscle (striated + involuntary)

Trick: Heart = involuntary but striated, so it is the trap option. Only gut movement is both involuntary and unstriated.

Answer: (C) Movement of food in the alimentary canal

Concept: Mature plant cells have one large central vacuole filled with cell sap.

1. It stores water, sugars, amino acids, salts and wastes
2. It keeps the cell turgid (turgor pressure), giving rigidity to the plant
3. Heredity = nucleus, respiration = mitochondria, protein synthesis = ribosomes

Yaad rakhein: A vacuole can take up 50–90% of a mature plant cell's volume; animal cells have small vacuoles.

Answer: (D) Store cell sap and help maintain turgor pressure.

Concept: Mass = amount of matter (constant); weight $W=mg$ (depends on g).

1. g changes from place to place (e.g. on the Moon it is about $\frac{1}{6}$ of Earth's)
2. So weight changes with location, but mass stays the same

Yaad rakhein: On the Moon your weight becomes about $\frac{1}{6}$, but your mass stays the same. Mass is measured in kg, weight in N.

Answer: (C) Mass stays the same everywhere, but weight changes with location.

Concept: Maximum electrons in a shell = $2n^2$; M is the 3rd shell ($n=3$).

1. Maximum in M = $2\times 3^2=18$
2. Ca (20): K = 2, L = 8, M = 8, N = 2, so M has 8 electrons

Yaad rakhein: The outermost shell cannot have more than 8 electrons, so after M has 8 the 19th and 20th electrons go to N.

Answer: (B) 18, 8

Concept: Average velocity = total displacement/time (not distance).

1. She swims there and back, so she ends at the start point and displacement = 0
2. Average velocity = $\frac{0}{60}=0$ m/s (average speed would be $\frac{240}{60}=4$ m/s)

Trick: Back to the starting point means velocity = 0. 4 m/s is the trap answer, since that is the average speed.

Answer: (A) 0 m/s

Concept: A condom is a barrier method: it stops sperm and body fluids from passing.

1. It prevents pregnancy and also reduces the spread of STDs like HIV-AIDS, gonorrhoea and syphilis
2. No method is 100% safe, so 'completely eliminate' (A) is wrong; it does not raise fertility or any law

Trick: Words like 'completely' or 'always' usually mark a wrong option. 'To some extent' is the realistic choice.

Answer: (C) Condoms help prevent the transmission of sexually transmitted diseases to some extent

Concept: The sky looks blue because air molecules scatter blue light.

1. At very high altitude the air is very thin, so there is very little scattering
2. Little scattered light reaches the eye, so the sky looks dark
3. Passengers are still inside the atmosphere, so B is wrong

Yaad rakhein: For the same reason the sky looks black from the Moon and to astronauts in space.

Answer: (A) Scattering of light is not prominent at such heights.

Concept: Hybridisation = crossing genetically dissimilar plants.

1. The aim is to bring desirable traits (high yield, disease resistance, quality) together in one variety
2. Types: intervarietal, interspecific, intergeneric
3. Cloning gives identical plants, which is the opposite of hybridisation

Yaad rakhein: Hybridisation was a key method behind the high-yielding wheat and rice varieties of the Green Revolution.

Answer: (B) To combine desirable traits by crossing genetically dissimilar plants

Concept: A soft iron core inside a current-carrying solenoid becomes a strong magnet only while current flows.

1. The magnetism is temporary, so it is an electromagnet
2. Soft iron loses its magnetism quickly when the current is switched off, so it is not a permanent magnet (steel is used for those)

Yaad rakhein: Electromagnets are used in electric bells, cranes for lifting scrap, relays and MRI machines.

Answer: (D) Electromagnet

Concept: $g=\frac{GM}{R^2}$, so $g\propto \frac{1}{R^2}$ when M is constant.

1. New g = $\frac{GM}{(2R{)}^2}=\frac{GM}{4R^2}$
2. $=\frac{g}{4}$, which is one-fourth

Trick: Inverse square: doubling R divides g by $2^2=4$; tripling it would divide g by 9.

Answer: (B) One-fourth

Concept: Olfactory indicators are substances whose smell changes in acidic or basic media.

1. Statement I is the correct definition
2. Onion and vanilla essence lose their smell in a base but keep it in an acid; clove oil is another example
3. So both statements are true

Yaad rakhein: Natural indicators: litmus (lichen), turmeric (turns red-brown in a base), red cabbage, hydrangea petals.

Answer: (A) Both statements I and II are true.

Concept: Carbon compounds are mostly covalent: they have no free ions and only weak intermolecular forces.

1. No ions means they are poor conductors of electricity, so Statement I is true
2. Weak forces between molecules give low melting and boiling points compared with ionic compounds, so Statement II is true

Yaad rakhein: Ionic compounds have high m.p. and conduct when molten/in solution. Covalent compounds have low m.p. and do not conduct.

Answer: (D) Both the statements are true.