RRB Technician Grade III 2024, 2025 PYQs

Concept: In fission a unicellular organism divides to form daughter cells.

1. Multiple fission (e.g. Plasmodium) – one cell gives many daughter cells.
2. Binary fission (e.g. Amoeba) – one cell divides into two cells.
3. So the analogy gives 'two cells'.

Yaad rakhein: Binary = two (bi = 2).

Answer: (B) two cells

Concept: $\text{Average speed}=\frac{\text{Total distance}}{\text{Total time}}$

1. Total distance $=60+80=140m$
2. Total time $=30+40=70s$
3. Average speed $=\frac{140}{70}=2\mathrm{m}{\mathrm{s}}^{-1}$

Trick: Both parts have speed $\frac{60}{30}=\frac{80}{40}=2$; equal speeds give the same average.

Answer: (D) 2 m s${}^{-1}$

Concept: Power $P=\frac{1}{f}$ ($f$ in metres). Negative power means a concave (diverging) lens.

1. $P=-0.5D$
2. $f=\frac{1}{P}=\frac{1}{-0.5}=-2.0m$
3. Negative $f$ → concave lens (used to correct myopia).

Yaad rakhein: Minus power = concave lens = myopia correction.

Answer: (C) –2.0 m, concave lens

Concept: A compound is formed by chemical combination of elements in a fixed ratio.

1. It is a chemical change, not a physical one.
2. Its constituents cannot be separated by physical methods.
3. The compound has properties totally different from its elements, e.g. $\mathrm{F}\mathrm{e}\mathrm{S}$ is not magnetic though iron is.

Yaad rakhein: Compound = new substance, new properties; mixture keeps old properties.

Answer: (C) The new product formed has totally different properties.

Concept: Pentane is an alkane (saturated); alkanes follow ${\mathrm{C}}_{\mathrm{n}}{\mathrm{H}}_{2\mathrm{n}+2}$.

1. 'Pent' means 5 carbons: $n=5$.
2. $2n+2=2\times 5+2=12$
3. Formula: ${\mathrm{C}}_5{\mathrm{H}}_{12}$

Yaad rakhein: Alkane ${\mathrm{C}}_{\mathrm{n}}{\mathrm{H}}_{2\mathrm{n}+2}$, alkene ${\mathrm{C}}_{\mathrm{n}}{\mathrm{H}}_{2\mathrm{n}}$, alkyne ${\mathrm{C}}_{\mathrm{n}}{\mathrm{H}}_{2\mathrm{n}-2}$.

Answer: (A) C₅H₁₂

Concept: Ligaments and tendons are fibrous connective tissues that join body parts.

1. Ligament – joins bone to bone; it is elastic.
2. Tendon – joins muscle to bone; it is strong with limited flexibility.
3. Cartilage smoothens joint surfaces; blood is a fluid connective tissue.

Yaad rakhein: Ligament: Bone–Bone; Tendon: Muscle–Bone.

Answer: (C) Tendon

Concept: A true solution is a homogeneous mixture with particles smaller than about $1\mathrm{n}\mathrm{m}$.

1. Particles are too small to be seen with the naked eye – statement A is false.
2. They do not settle down when left undisturbed – true.
3. They cannot be separated by filtration – true; it is homogeneous – true.

Yaad rakhein: Solution particles: invisible, non-settling, pass through filter paper.

Answer: (A) Particles of the solution can be seen by the naked eye.

Concept: The stomach secretes hydrochloric acid, so gastric juice is strongly acidic.

1. HCl in the stomach activates pepsin and kills germs.
2. pH of gastric juice ≈ 1.2.
3. For comparison: blood ≈ 7.4 (slightly basic); lemon juice ≈ 2.2.

Yaad rakhein: Stomach ≈ 1.2, Lemon ≈ 2.2, Blood ≈ 7.4.

Answer: (C) 1.2

Concept: In electrolytic refining, impure metal is the anode, pure metal is the cathode and a solution of a soluble salt of that metal is the electrolyte.

1. Example (copper): anode – impure Cu; cathode – thin strip of pure Cu.
2. Electrolyte – acidified $\mathrm{C}\mathrm{u}\mathrm{S}{\mathrm{O}}_4$ solution (a metal salt).
3. On passing current, pure metal deposits on the cathode; impurities fall as anode mud.

Yaad rakhein: Anode = impure, Cathode = pure, Electrolyte = metal salt solution.

Answer: (C) Metal salt

Concept: Speed = distance ÷ time; one round of a circle covers its circumference $2\pi r$.

1. Distance in one round $=2\pi r$
2. Time taken $t=2s$
3. $v=\frac{2\pi r}{2}=\pi r$ metre/second

Trick: $v=\frac{2\pi r}{T}$; put $T=2$ and the 2's cancel.

Answer: (B) $\pi r$ metre/second

Concept: Ozone (${\mathrm{O}}_3$) in the stratosphere absorbs harmful UV rays; synthetic CFCs destroy it.

1. CFCs were used as refrigerants and in fire extinguishers/aerosols.
2. In the upper atmosphere UV light releases chlorine atoms from CFCs.
3. Chlorine breaks down ozone, so ozone levels dropped sharply (from 1980s).

Yaad rakhein: CFC → chlorine → ozone hole. Montreal Protocol (1987) limits CFCs.

Answer: (B) Chlorofluorocarbons

Concept: Pascal's law: pressure applied to a confined fluid is transmitted undiminished in all directions.

1. Fluid particles push equally on every side.
2. Pressure applied at one point reaches every part of the fluid and the container walls equally.
3. Used in hydraulic lifts, hydraulic brakes and presses.

Yaad rakhein: Pascal = all directions, undiminished → hydraulic lift.

Answer: (B) Undiminished in all directions.

Concept: $T{(}^{\circ }C)=T(K)-273$

1. Given $T=298K$
2. $298-273=25$
3. So the temperature is ${25}^{\circ }C$ (room temperature).

Yaad rakhein: K → °C: subtract 273; °C → K: add 273.

Answer: (C) 25 degree Celsius

Concept: Arrhenius idea: acids give ${\mathrm{H}}^{+}$ ions and bases give $\mathrm{O}{\mathrm{H}}^{-}$ ions in water.

1. $\mathrm{H}\mathrm{C}\mathrm{l}\to {\mathrm{H}}^{+}+\mathrm{C}{\mathrm{l}}^{-}$ (in water ${\mathrm{H}}^{+}$ forms ${\mathrm{H}}_3{\mathrm{O}}^{+}$).
2. $\mathrm{N}\mathrm{a}\mathrm{O}\mathrm{H}\to \mathrm{N}{\mathrm{a}}^{+}+\mathrm{O}{\mathrm{H}}^{-}$
3. So acid → ${\mathrm{H}}^{+}$, base → $\mathrm{O}{\mathrm{H}}^{-}$.

Yaad rakhein: Acid – ${\mathrm{H}}^{+}$; Base – $\mathrm{O}{\mathrm{H}}^{-}$; together they form water (neutralisation).

Answer: (B) H⁺ ions and OH^- ions, respectively

Concept: Ohm's law: $V=IR$

1. $I=2A$, $R=12\Omega$
2. $V=2\times 12=24V$

Trick: Remember the triangle V on top, I and R below: $V=IR$, $I=\frac{V}{R}$, $R=\frac{V}{I}$.

Answer: (B) 24 V

Concept: Work done $W=F\times s$ (force along the displacement).

1. $F=5N$, $s=3m$
2. $W=5\times 3=15J$

Yaad rakhein: $1J=1N\times 1m$.

Answer: (D) 15 J

Concept: Inside a long current-carrying solenoid the field lines are straight, parallel to the axis and equally spaced – a uniform field.

1. Uniform field ⇒ same at all points inside (C, D true).
2. Lines run along the axis, parallel to each other (A true).
3. Magnetic field lines never intersect and are not ellipsoidal inside – B is NOT true.

Yaad rakhein: Field lines never cross – two directions at one point is impossible.

Answer: (B) Ellipsoidal and intersects with each other

Concept: $W=F\times s\Rightarrow s=\frac{W}{F}$

1. $W=3J$, $F=2N$
2. $s=\frac{3}{2}=1.5m$

Trick: Check: $2\times 1.5=3$ ✔.

Answer: (A) 1.5 m

Concept: Heating ferrous sulphate crystals is a thermal decomposition reaction.

1. $2\mathrm{F}\mathrm{e}\mathrm{S}{\mathrm{O}}_4(\mathrm{s})\stackrel{\mathrm{h}\mathrm{e}\mathrm{a}\mathrm{t}}{\to }\mathrm{F}{\mathrm{e}}_2{\mathrm{O}}_3(\mathrm{s})+\mathrm{S}{\mathrm{O}}_2(\mathrm{g})+\mathrm{S}{\mathrm{O}}_3(\mathrm{g})$
2. Products: ferric oxide, sulphur dioxide, sulphur trioxide.
3. Sulphuric acid is not formed; green crystals first lose water and turn white, then brown.

Yaad rakhein: $\mathrm{F}\mathrm{e}\mathrm{S}{\mathrm{O}}_4$ on heating → $\mathrm{F}{\mathrm{e}}_2{\mathrm{O}}_3$ + $\mathrm{S}{\mathrm{O}}_2$ + $\mathrm{S}{\mathrm{O}}_3$ (smell of burning sulphur).

Answer: (D) Sulphuric acid

Concept: Displacement is the shortest distance from the initial to the final position.

1. Path: A → B (20 m) → A (20 m).
2. Distance travelled $=20+20=40m$.
3. Initial and final positions are both A, so displacement $=0m$.

Yaad rakhein: Back to start ⇒ displacement zero, though distance is not.

Answer: (B) 0 m