80 marks · 3 hours · 43 questions · NIOS board pattern (312/TUS/104A)
Full syllabus · Mechanics & fluids
43 Q · 80 marks
Full syllabus · E&M & optics
43 Q · 80 marks
Full syllabus · Modern physics & semiconductors
43 Q · 80 marks
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Q1. A 4 kg block on a smooth table is pulled by a 12 N horizontal force. What is its acceleration?
How to approach: Read all four options. Eliminate choices with wrong units, sign or formula. Select the option matching NIOS textbook/PYQ.
NIOS marking: NIOS awards 1 mark all-or-nothing for the correct option. No partial marking in Section A MCQ.
Example: Example: F = ma with m = 2 kg, a = 3 m·s⁻² → F = 6 N (not 5 N or 6 kg).
Common mistakes: Picking a plausible but wrong formula; unit mismatch; confusing similar laws (e.g. Lenz vs Fleming).
Model answer: F = ma → a = F/m = 12/4 = 3 m·s⁻² (Newton's second law, L3).
Q2. A 0.5 kg ball moves at 4 m·s⁻¹. Its kinetic energy is:
How to approach: Read all four options. Eliminate choices with wrong units, sign or formula. Select the option matching NIOS textbook/PYQ.
NIOS marking: NIOS awards 1 mark all-or-nothing for the correct option. No partial marking in Section A MCQ.
Example: Example: F = ma with m = 2 kg, a = 3 m·s⁻² → F = 6 N (not 5 N or 6 kg).
Common mistakes: Picking a plausible but wrong formula; unit mismatch; confusing similar laws (e.g. Lenz vs Fleming).
Model answer: K = ½mv² = ½ × 0.5 × 16 = 4 J.
Q3. According to Archimedes' principle, the buoyant force on a body equals:
How to approach: Read all four options. Eliminate choices with wrong units, sign or formula. Select the option matching NIOS textbook/PYQ.
NIOS marking: NIOS awards 1 mark all-or-nothing for the correct option. No partial marking in Section A MCQ.
Example: Example: F = ma with m = 2 kg, a = 3 m·s⁻² → F = 6 N (not 5 N or 6 kg).
Common mistakes: Picking a plausible but wrong formula; unit mismatch; confusing similar laws (e.g. Lenz vs Fleming).
Model answer: Buoyant force = weight of the fluid displaced by the submerged part of the body.
Q4. A Carnot engine operates between 500 K and 300 K. Its maximum efficiency is:
How to approach: Read all four options. Eliminate choices with wrong units, sign or formula. Select the option matching NIOS textbook/PYQ.
NIOS marking: NIOS awards 1 mark all-or-nothing for the correct option. No partial marking in Section A MCQ.
Example: Example: F = ma with m = 2 kg, a = 3 m·s⁻² → F = 6 N (not 5 N or 6 kg).
Common mistakes: Picking a plausible but wrong formula; unit mismatch; confusing similar laws (e.g. Lenz vs Fleming).
Model answer: η = 1 − T₂/T₁ = 1 − 300/500 = 0.40 = 40%.
Q5. A wave has frequency 200 Hz and wavelength 1.7 m. Its speed is:
How to approach: Read all four options. Eliminate choices with wrong units, sign or formula. Select the option matching NIOS textbook/PYQ.
NIOS marking: NIOS awards 1 mark all-or-nothing for the correct option. No partial marking in Section A MCQ.
Example: Example: F = ma with m = 2 kg, a = 3 m·s⁻² → F = 6 N (not 5 N or 6 kg).
Common mistakes: Picking a plausible but wrong formula; unit mismatch; confusing similar laws (e.g. Lenz vs Fleming).
Model answer: v = fλ = 200 × 1.7 = 340 m·s⁻¹.
Q6. The SI unit of electric field intensity is:
How to approach: Read all four options. Eliminate choices with wrong units, sign or formula. Select the option matching NIOS textbook/PYQ.
NIOS marking: NIOS awards 1 mark all-or-nothing for the correct option. No partial marking in Section A MCQ.
Example: Example: F = ma with m = 2 kg, a = 3 m·s⁻² → F = 6 N (not 5 N or 6 kg).
Common mistakes: Picking a plausible but wrong formula; unit mismatch; confusing similar laws (e.g. Lenz vs Fleming).
Model answer: E = F/q → unit N·C⁻¹ (also equivalent to V·m⁻¹).
Q7. Energy stored in a capacitor C charged to potential V is:
How to approach: Read all four options. Eliminate choices with wrong units, sign or formula. Select the option matching NIOS textbook/PYQ.
NIOS marking: NIOS awards 1 mark all-or-nothing for the correct option. No partial marking in Section A MCQ.
Example: Example: F = ma with m = 2 kg, a = 3 m·s⁻² → F = 6 N (not 5 N or 6 kg).
Common mistakes: Picking a plausible but wrong formula; unit mismatch; confusing similar laws (e.g. Lenz vs Fleming).
Model answer: U = ½CV² (energy stored in electric field between plates).
Q8. A 10 Ω resistor carries 2 A current. Power dissipated is:
How to approach: Read all four options. Eliminate choices with wrong units, sign or formula. Select the option matching NIOS textbook/PYQ.
NIOS marking: NIOS awards 1 mark all-or-nothing for the correct option. No partial marking in Section A MCQ.
Example: Example: F = ma with m = 2 kg, a = 3 m·s⁻² → F = 6 N (not 5 N or 6 kg).
Common mistakes: Picking a plausible but wrong formula; unit mismatch; confusing similar laws (e.g. Lenz vs Fleming).
Model answer: P = I²R = 4 × 10 = 40 W.
Q9. Fleming's left-hand rule is used to find the direction of:
How to approach: Read all four options. Eliminate choices with wrong units, sign or formula. Select the option matching NIOS textbook/PYQ.
NIOS marking: NIOS awards 1 mark all-or-nothing for the correct option. No partial marking in Section A MCQ.
Example: Example: F = ma with m = 2 kg, a = 3 m·s⁻² → F = 6 N (not 5 N or 6 kg).
Common mistakes: Picking a plausible but wrong formula; unit mismatch; confusing similar laws (e.g. Lenz vs Fleming).
Model answer: Left-hand rule gives direction of force on conductor carrying current in external B field.
Q10. In a step-down transformer, the secondary coil has:
How to approach: Read all four options. Eliminate choices with wrong units, sign or formula. Select the option matching NIOS textbook/PYQ.
NIOS marking: NIOS awards 1 mark all-or-nothing for the correct option. No partial marking in Section A MCQ.
Example: Example: F = ma with m = 2 kg, a = 3 m·s⁻² → F = 6 N (not 5 N or 6 kg).
Common mistakes: Picking a plausible but wrong formula; unit mismatch; confusing similar laws (e.g. Lenz vs Fleming).
Model answer: Step-down: N_s < N_p so V_s < V_p (V ∝ N).
Q11. In a prism, violet light is deviated more than red because:
How to approach: Read all four options. Eliminate choices with wrong units, sign or formula. Select the option matching NIOS textbook/PYQ.
NIOS marking: NIOS awards 1 mark all-or-nothing for the correct option. No partial marking in Section A MCQ.
Example: Example: F = ma with m = 2 kg, a = 3 m·s⁻² → F = 6 N (not 5 N or 6 kg).
Common mistakes: Picking a plausible but wrong formula; unit mismatch; confusing similar laws (e.g. Lenz vs Fleming).
Model answer: μ increases as λ decreases; δ ∝ (μ−1) so violet bends more.
Q12. In Young's double-slit experiment, fringe width β is proportional to:
How to approach: Read all four options. Eliminate choices with wrong units, sign or formula. Select the option matching NIOS textbook/PYQ.
NIOS marking: NIOS awards 1 mark all-or-nothing for the correct option. No partial marking in Section A MCQ.
Example: Example: F = ma with m = 2 kg, a = 3 m·s⁻² → F = 6 N (not 5 N or 6 kg).
Common mistakes: Picking a plausible but wrong formula; unit mismatch; confusing similar laws (e.g. Lenz vs Fleming).
Model answer: β = λD/d — fringe width proportional to wavelength λ.
Q13. In Bohr model of hydrogen, angular momentum in nth orbit is:
How to approach: Read all four options. Eliminate choices with wrong units, sign or formula. Select the option matching NIOS textbook/PYQ.
NIOS marking: NIOS awards 1 mark all-or-nothing for the correct option. No partial marking in Section A MCQ.
Example: Example: F = ma with m = 2 kg, a = 3 m·s⁻² → F = 6 N (not 5 N or 6 kg).
Common mistakes: Picking a plausible but wrong formula; unit mismatch; confusing similar laws (e.g. Lenz vs Fleming).
Model answer: Quantisation: mvr = nh/(2π).
Q14. Photoelectric effect demonstrates that light energy is:
How to approach: Read all four options. Eliminate choices with wrong units, sign or formula. Select the option matching NIOS textbook/PYQ.
NIOS marking: NIOS awards 1 mark all-or-nothing for the correct option. No partial marking in Section A MCQ.
Example: Example: F = ma with m = 2 kg, a = 3 m·s⁻² → F = 6 N (not 5 N or 6 kg).
Common mistakes: Picking a plausible but wrong formula; unit mismatch; confusing similar laws (e.g. Lenz vs Fleming).
Model answer: Einstein: E = hν — emission needs hν > work function φ₀.
Q15. Half-life of a radioactive sample is the time in which:
How to approach: Read all four options. Eliminate choices with wrong units, sign or formula. Select the option matching NIOS textbook/PYQ.
NIOS marking: NIOS awards 1 mark all-or-nothing for the correct option. No partial marking in Section A MCQ.
Example: Example: F = ma with m = 2 kg, a = 3 m·s⁻² → F = 6 N (not 5 N or 6 kg).
Common mistakes: Picking a plausible but wrong formula; unit mismatch; confusing similar laws (e.g. Lenz vs Fleming).
Model answer: T₁/₂ = 0.693/λ — time for activity (or number of nuclei) to halve.
Q16. Nuclear fission is best described as:
How to approach: Read all four options. Eliminate choices with wrong units, sign or formula. Select the option matching NIOS textbook/PYQ.
NIOS marking: NIOS awards 1 mark all-or-nothing for the correct option. No partial marking in Section A MCQ.
Example: Example: F = ma with m = 2 kg, a = 3 m·s⁻² → F = 6 N (not 5 N or 6 kg).
Common mistakes: Picking a plausible but wrong formula; unit mismatch; confusing similar laws (e.g. Lenz vs Fleming).
Model answer: Fission: heavy nucleus (e.g. ²³⁵U) splits — releases ~200 MeV per event.
Q17. Define intrinsic semiconductor. Name the two charge carriers at room temperature. (25–35 words.)
Suggested length: up to 30 words · 2 marks
0 / 30 words
How to approach: Answer in 25–35 words. For numerical/fill items: state formula, substitute values, give final answer with units.
NIOS marking: 2 marks = 2 sub-parts × 1 mark each — correct formula/match (1) + correct value/term (1).
Example: Example: P = ρgh → P = 1000×10×2 = 2×10⁴ Pa.
Common mistakes: Formula without value; value without units; exceeding word limit; vague one-word answers.
Model answer: Pure semiconductor (Ge or Si) without intentional doping. At room temperature thermal excitation creates equal numbers of free electrons and holes for conduction.
Q18. State one advantage of LED over ordinary bulb. What determines LED colour? (25–35 words.)
Suggested length: up to 30 words · 2 marks
0 / 30 words
How to approach: Answer in 25–35 words. For numerical/fill items: state formula, substitute values, give final answer with units.
NIOS marking: 2 marks = 2 sub-parts × 1 mark each — correct formula/match (1) + correct value/term (1).
Example: Example: P = ρgh → P = 1000×10×2 = 2×10⁴ Pa.
Common mistakes: Formula without value; value without units; exceeding word limit; vague one-word answers.
Model answer: LED converts more electrical energy to light (low heat loss). Colour depends on semiconductor band-gap energy — determines photon energy hν emitted.
Q19. A 0.2 kg ball moving at 10 m·s⁻¹ is stopped in 0.04 s. Find impulse and average force. (25–35 words.)
Suggested length: up to 35 words · 2 marks
0 / 35 words
How to approach: Answer in 25–35 words. For numerical/fill items: state formula, substitute values, give final answer with units.
NIOS marking: 2 marks = 2 sub-parts × 1 mark each — correct formula/match (1) + correct value/term (1).
Example: Example: P = ρgh → P = 1000×10×2 = 2×10⁴ Pa.
Common mistakes: Formula without value; value without units; exceeding word limit; vague one-word answers.
Model answer: Impulse = Δp = 0 − 0.2×10 = −2 N·s (magnitude 2 N·s). F_avg = Δp/Δt = 2/0.04 = 50 N opposite to initial motion.
Q20. State work-energy theorem. How much work is needed to stop a 3 kg object moving at 6 m·s⁻¹? (25–35 words.)
Suggested length: up to 35 words · 2 marks
0 / 35 words
How to approach: Answer in 25–35 words. For numerical/fill items: state formula, substitute values, give final answer with units.
NIOS marking: 2 marks = 2 sub-parts × 1 mark each — correct formula/match (1) + correct value/term (1).
Example: Example: P = ρgh → P = 1000×10×2 = 2×10⁴ Pa.
Common mistakes: Formula without value; value without units; exceeding word limit; vague one-word answers.
Model answer: Work done on a body equals change in its kinetic energy (W = ΔK). K = ½mv² = ½×3×36 = 54 J; work = −54 J to stop it.
Q21. State Bernoulli's principle in one line. Why does air speed increase over an aircraft wing top? (25–35 words.)
Suggested length: up to 30 words · 2 marks
0 / 30 words
How to approach: Answer in 25–35 words. For numerical/fill items: state formula, substitute values, give final answer with units.
NIOS marking: 2 marks = 2 sub-parts × 1 mark each — correct formula/match (1) + correct value/term (1).
Example: Example: P = ρgh → P = 1000×10×2 = 2×10⁴ Pa.
Common mistakes: Formula without value; value without units; exceeding word limit; vague one-word answers.
Model answer: Along a streamline, higher fluid speed means lower pressure (P + ½ρv² + ρgh = constant). Curved upper surface forces longer path → faster flow → lower pressure above.
Q22. Write first law of thermodynamics. If ΔQ = +300 J and ΔW = +100 J (by system), find ΔU. (25–35 words.)
Suggested length: up to 35 words · 2 marks
0 / 35 words
How to approach: Answer in 25–35 words. For numerical/fill items: state formula, substitute values, give final answer with units.
NIOS marking: 2 marks = 2 sub-parts × 1 mark each — correct formula/match (1) + correct value/term (1).
Example: Example: P = ρgh → P = 1000×10×2 = 2×10⁴ Pa.
Common mistakes: Formula without value; value without units; exceeding word limit; vague one-word answers.
Model answer: ΔQ = ΔU + ΔW. Heat to system +300 J, work done by system +100 J: ΔU = ΔQ − ΔW = 300 − 100 = 200 J.
Q23. Define Doppler effect. When source approaches stationary listener, is observed frequency higher or lower? (25–35 words.)
Suggested length: up to 30 words · 2 marks
0 / 30 words
How to approach: Answer in 25–35 words. For numerical/fill items: state formula, substitute values, give final answer with units.
NIOS marking: 2 marks = 2 sub-parts × 1 mark each — correct formula/match (1) + correct value/term (1).
Example: Example: P = ρgh → P = 1000×10×2 = 2×10⁴ Pa.
Common mistakes: Formula without value; value without units; exceeding word limit; vague one-word answers.
Model answer: Change in observed frequency due to relative motion of source and observer. When source approaches, wavefronts compress — observed frequency is higher (pitch rises).
Q24. State Gauss's law in words. What is the net flux through a closed surface enclosing no charge? (25–35 words.)
Suggested length: up to 30 words · 2 marks
0 / 30 words
How to approach: Answer in 25–35 words. For numerical/fill items: state formula, substitute values, give final answer with units.
NIOS marking: 2 marks = 2 sub-parts × 1 mark each — correct formula/match (1) + correct value/term (1).
Example: Example: P = ρgh → P = 1000×10×2 = 2×10⁴ Pa.
Common mistakes: Formula without value; value without units; exceeding word limit; vague one-word answers.
Model answer: Total electric flux through a closed surface equals q_enclosed/ε₀. With no charge inside, net flux is zero — field lines entering equal those leaving.
Q25. Two capacitors 6 μF and 3 μF are in series. Find equivalent capacitance. (25–35 words.)
Suggested length: up to 35 words · 2 marks
0 / 35 words
How to approach: Answer in 25–35 words. For numerical/fill items: state formula, substitute values, give final answer with units.
NIOS marking: 2 marks = 2 sub-parts × 1 mark each — correct formula/match (1) + correct value/term (1).
Example: Example: P = ρgh → P = 1000×10×2 = 2×10⁴ Pa.
Common mistakes: Formula without value; value without units; exceeding word limit; vague one-word answers.
Model answer: 1/C_s = 1/6 + 1/3 = 1/2 μF⁻¹ → C_s = 2 μF. In series, same charge; voltages add.
Q26. State Ohm's law. A wire of resistance 5 Ω carries 3 A. Find potential difference. (25–35 words.)
Suggested length: up to 30 words · 2 marks
0 / 30 words
How to approach: Answer in 25–35 words. For numerical/fill items: state formula, substitute values, give final answer with units.
NIOS marking: 2 marks = 2 sub-parts × 1 mark each — correct formula/match (1) + correct value/term (1).
Example: Example: P = ρgh → P = 1000×10×2 = 2×10⁴ Pa.
Common mistakes: Formula without value; value without units; exceeding word limit; vague one-word answers.
Model answer: V = IR (at constant temperature). V = 5 × 3 = 15 V across the wire.
Q27. Write the force on a wire of length L carrying current I in field B (θ = 90°). Find F if B = 0.2 T, I = 5 A, L = 0.4 m. (25–35 words.)
Suggested length: up to 35 words · 2 marks
0 / 35 words
How to approach: Answer in 25–35 words. For numerical/fill items: state formula, substitute values, give final answer with units.
NIOS marking: 2 marks = 2 sub-parts × 1 mark each — correct formula/match (1) + correct value/term (1).
Example: Example: P = ρgh → P = 1000×10×2 = 2×10⁴ Pa.
Common mistakes: Formula without value; value without units; exceeding word limit; vague one-word answers.
Model answer: F = BIL sin θ; at 90°, F = BIL = 0.2 × 5 × 0.4 = 0.4 N. Direction from Fleming's left-hand rule.
Q28. State Lenz's law. When north pole approaches a coil, which pole does the coil's near face behave as? (25–35 words.)
Suggested length: up to 30 words · 2 marks
0 / 30 words
How to approach: Answer in 25–35 words. For numerical/fill items: state formula, substitute values, give final answer with units.
NIOS marking: 2 marks = 2 sub-parts × 1 mark each — correct formula/match (1) + correct value/term (1).
Example: Example: P = ρgh → P = 1000×10×2 = 2×10⁴ Pa.
Common mistakes: Formula without value; value without units; exceeding word limit; vague one-word answers.
Model answer: Induced effects oppose the cause of flux change. Approaching north increases flux — coil's near face acts as north pole to repel it (induced current opposes increase).
Q29. Why does a prism produce a spectrum from white light? Name the phenomenon. (30–50 words.)
Suggested length: up to 45 words · 2 marks
0 / 45 words
How to approach: Write 30–50 words. Open with the law/formula/name, then one-line explanation or numerical step.
NIOS marking: 2 marks = correct law/formula (1) + brief explanation/application (1).
Example: Example: Lenz's law — induced current opposes the change in magnetic flux causing it.
Common mistakes: Long derivation; missing law statement; wrong units; copying notes without answering the question.
Model answer: White light contains many wavelengths. Refractive index μ varies with λ — violet bends more than red. Separation of colours on refraction is dispersion, producing a visible spectrum.
Q30. Distinguish interference and diffraction in one sentence each. (30–50 words.)
Suggested length: up to 45 words · 2 marks
0 / 45 words
How to approach: Write 30–50 words. Open with the law/formula/name, then one-line explanation or numerical step.
NIOS marking: 2 marks = correct law/formula (1) + brief explanation/application (1).
Example: Example: Lenz's law — induced current opposes the change in magnetic flux causing it.
Common mistakes: Long derivation; missing law statement; wrong units; copying notes without answering the question.
Model answer: Interference: superposition of waves from coherent sources giving alternate bright/dark fringes. Diffraction: spreading of waves around edges or through apertures — bending of wavefronts (Huygens principle).
Q31. State one success and one limitation of Rutherford's nuclear model. (30–50 words.)
Suggested length: up to 45 words · 2 marks
0 / 45 words
How to approach: Write 30–50 words. Open with the law/formula/name, then one-line explanation or numerical step.
NIOS marking: 2 marks = correct law/formula (1) + brief explanation/application (1).
Example: Example: Lenz's law — induced current opposes the change in magnetic flux causing it.
Common mistakes: Long derivation; missing law statement; wrong units; copying notes without answering the question.
Model answer: Success: explained scattering — concentrated positive charge (nucleus) with orbiting electrons. Limitation: accelerating electron should radiate and spiral into nucleus; could not explain line spectra.
Q32. Write de Broglie relation. Why are matter waves of macroscopic objects not observable? (30–50 words.)
Suggested length: up to 45 words · 2 marks
0 / 45 words
How to approach: Write 30–50 words. Open with the law/formula/name, then one-line explanation or numerical step.
NIOS marking: 2 marks = correct law/formula (1) + brief explanation/application (1).
Example: Example: Lenz's law — induced current opposes the change in magnetic flux causing it.
Common mistakes: Long derivation; missing law statement; wrong units; copying notes without answering the question.
Model answer: λ = h/p = h/(mv). Macroscopic bodies have very large mass → extremely small λ (<< atomic size) — wave nature undetectable; diffraction/interference negligible.
Q33. Define mass defect and binding energy of a nucleus. (30–50 words.)
Suggested length: up to 45 words · 2 marks
0 / 45 words
How to approach: Write 30–50 words. Open with the law/formula/name, then one-line explanation or numerical step.
NIOS marking: 2 marks = correct law/formula (1) + brief explanation/application (1).
Example: Example: Lenz's law — induced current opposes the change in magnetic flux causing it.
Common mistakes: Long derivation; missing law statement; wrong units; copying notes without answering the question.
Model answer: Mass defect Δm = (Z m_p + N m_n) − M_nucleus. Binding energy is energy equivalent E_b = Δm c² needed to separate nucleus into nucleons — measures nuclear stability.
Q34. Write the fusion reaction in the Sun (proton-proton chain outline). Why is high temperature needed? (30–50 words.)
Suggested length: up to 50 words · 2 marks
0 / 50 words
How to approach: Write 30–50 words. Open with the law/formula/name, then one-line explanation or numerical step.
NIOS marking: 2 marks = correct law/formula (1) + brief explanation/application (1).
Example: Example: Lenz's law — induced current opposes the change in magnetic flux causing it.
Common mistakes: Long derivation; missing law statement; wrong units; copying notes without answering the question.
Model answer: Light nuclei fuse: e.g. 4 ¹H → ⁴He + energy + neutrinos. High temperature gives nuclei enough kinetic energy to overcome Coulomb repulsion and come within nuclear range.
Q35. What is doping? Distinguish n-type and p-type semiconductors. (30–50 words.)
Suggested length: up to 45 words · 2 marks
0 / 45 words
How to approach: Write 30–50 words. Open with the law/formula/name, then one-line explanation or numerical step.
NIOS marking: 2 marks = correct law/formula (1) + brief explanation/application (1).
Example: Example: Lenz's law — induced current opposes the change in magnetic flux causing it.
Common mistakes: Long derivation; missing law statement; wrong units; copying notes without answering the question.
Model answer: Doping adds controlled impurities. n-type: pentavalent donor (e.g. P in Si) gives extra electrons — majority carriers electrons. p-type: trivalent acceptor (e.g. Al) creates holes — majority carriers holes.
Q36. How does a p-n junction diode allow current in forward bias but block in reverse bias? (30–50 words.)
Suggested length: up to 50 words · 2 marks
0 / 50 words
How to approach: Write 30–50 words. Open with the law/formula/name, then one-line explanation or numerical step.
NIOS marking: 2 marks = correct law/formula (1) + brief explanation/application (1).
Example: Example: Lenz's law — induced current opposes the change in magnetic flux causing it.
Common mistakes: Long derivation; missing law statement; wrong units; copying notes without answering the question.
Model answer: Forward bias narrows depletion layer and lowers barrier — majority carriers cross easily, large current. Reverse bias widens depletion layer — only tiny leakage current until breakdown.
Q37. State Newton's three laws of motion in brief. (30–50 words.)
Suggested length: up to 50 words · 2 marks
0 / 50 words
How to approach: Write 30–50 words. Open with the law/formula/name, then one-line explanation or numerical step.
NIOS marking: 2 marks = correct law/formula (1) + brief explanation/application (1).
Example: Example: Lenz's law — induced current opposes the change in magnetic flux causing it.
Common mistakes: Long derivation; missing law statement; wrong units; copying notes without answering the question.
Model answer: First: body remains at rest or uniform motion unless acted by net external force. Second: F = ma — acceleration proportional to net force. Third: every action has equal and opposite reaction.
Q38. A 2 kg block slides down a frictionless incline of height 5 m. Find speed at bottom using energy conservation. (g = 10 m·s⁻², 50–80 words.)
Suggested length: up to 75 words · 3 marks
0 / 75 words
How to approach: Structure: formula/diagram (1) → substitution/working (1) → final answer with units (1). Use 50–80 words.
NIOS marking: 3 marks = formula or labelled diagram (1) + correct working (1) + answer with units (1).
Example: Example: W = mgh = 5×10×2 = 100 J work done against gravity.
Common mistakes: Skipping working; missing units; wrong sign convention; diagram without labels.
Model answer: Initial K = 0, PE = mgh = 2×10×5 = 100 J. At bottom PE = 0, so ½mv² = 100 → v² = 100 → v = 10 m·s⁻¹. Mechanical energy conserved on frictionless path.
Q39. Calculate gauge pressure at 8 m depth in water and total pressure if atmospheric pressure is 1.01×10⁵ Pa. (ρ = 1000 kg·m⁻³, g = 10 m·s⁻², 50–80 words.)
Suggested length: up to 75 words · 3 marks
0 / 75 words
How to approach: Structure: formula/diagram (1) → substitution/working (1) → final answer with units (1). Use 50–80 words.
NIOS marking: 3 marks = formula or labelled diagram (1) + correct working (1) + answer with units (1).
Example: Example: W = mgh = 5×10×2 = 100 J work done against gravity.
Common mistakes: Skipping working; missing units; wrong sign convention; diagram without labels.
Model answer: Gauge pressure P_g = ρgh = 1000×10×8 = 8×10⁴ Pa. Total absolute pressure P = P_atm + P_g = 1.01×10⁵ + 0.8×10⁵ = 1.81×10⁵ Pa.
Q40. An ideal gas expands isothermally at 300 K from 2 L to 4 L. Write expression for work done and sign of ΔU. (50–80 words.)
Suggested length: up to 75 words · 3 marks
0 / 75 words
How to approach: Structure: formula/diagram (1) → substitution/working (1) → final answer with units (1). Use 50–80 words.
NIOS marking: 3 marks = formula or labelled diagram (1) + correct working (1) + answer with units (1).
Example: Example: W = mgh = 5×10×2 = 100 J work done against gravity.
Common mistakes: Skipping working; missing units; wrong sign convention; diagram without labels.
Model answer: Isothermal: temperature constant → ΔU = 0 for ideal gas. Work by gas W = nRT ln(V₂/V₁) = nRT ln 2 (positive for expansion). Heat absorbed Q = W.
Q41. An LCR series circuit has R = 10 Ω, L = 0.1 H, C = 100 μF. Find resonant frequency and impedance at resonance. (50–80 words.)
Suggested length: up to 80 words · 3 marks
0 / 80 words
How to approach: Structure: formula/diagram (1) → substitution/working (1) → final answer with units (1). Use 50–80 words.
NIOS marking: 3 marks = formula or labelled diagram (1) + correct working (1) + answer with units (1).
Example: Example: W = mgh = 5×10×2 = 100 J work done against gravity.
Common mistakes: Skipping working; missing units; wrong sign convention; diagram without labels.
Model answer: ν_r = 1/(2π√LC) = 1/(2π√(0.1 × 10⁻⁴)) ≈ 50.3 Hz. At resonance X_L = X_C, so Z = R = 10 Ω (minimum) and current is maximum.
Q42. State Coulomb's law. Derive electric field at distance r from a point charge +q. Explain why field lines radiate outward from positive charge. (80–120 words.)
Suggested length: up to 110 words · 5 marks
0 / 110 words
How to approach: Plan 80–120 words: state law/principle (1) → formula/diagram (1) → derivation or worked example (2) → conclusion (1).
NIOS marking: 5 marks = statement of law (1) + diagram/formula (1) + derivation/working (2) + conclusion with units (1).
Example: Example: State Gauss's law, draw Gaussian surface, derive E = σ/(2ε₀) for infinite sheet, note direction.
Common mistakes: Only definition without working; no diagram where required; arithmetic errors; missing conclusion.
Model answer: Coulomb: F = kq₁q₂/r² along line joining charges (k = 1/(4πε₀)). Field E = F/q₀ = kq/r² directed radially outward for +q. Test positive charge experiences repulsive force along radius — field lines start on + charge and point outward, never cross, density shows field strength.
Q43. Explain Bohr's postulates for hydrogen atom. Show how second postulate leads to quantised energy E_n = −13.6/n² eV. Relate to line spectrum. (80–120 words.)
Suggested length: up to 115 words · 5 marks
0 / 115 words
How to approach: Plan 80–120 words: state law/principle (1) → formula/diagram (1) → derivation or worked example (2) → conclusion (1).
NIOS marking: 5 marks = statement of law (1) + diagram/formula (1) + derivation/working (2) + conclusion with units (1).
Example: Example: State Gauss's law, draw Gaussian surface, derive E = σ/(2ε₀) for infinite sheet, note direction.
Common mistakes: Only definition without working; no diagram where required; arithmetic errors; missing conclusion.
Model answer: Postulates: (1) electrons revolve in certain stable orbits without radiation; (2) angular momentum mvr = nh/(2π); (3) radiation occurs only on transition between orbits with hν = E_i − E_f. Centripetal force gives r ∝ n² and E_n ∝ −1/n² → E_n = −13.6/n² eV for hydrogen. Transitions between levels emit/absorb photons of definite frequency — Balmer/Lyman line spectra.
Q1. A book rests on a table. The reaction force to the book's weight acts on:
How to approach: Read all four options. Eliminate choices with wrong units, sign or formula. Select the option matching NIOS textbook/PYQ.
NIOS marking: NIOS awards 1 mark all-or-nothing for the correct option. No partial marking in Section A MCQ.
Example: Example: F = ma with m = 2 kg, a = 3 m·s⁻² → F = 6 N (not 5 N or 6 kg).
Common mistakes: Picking a plausible but wrong formula; unit mismatch; confusing similar laws (e.g. Lenz vs Fleming).
Model answer: Third law pair: book pushes table down; table pushes book up — reaction to book's weight on book is table's normal force.
Q2. A spring (k = 100 N·m⁻¹) is stretched by 0.2 m. Elastic PE stored is:
How to approach: Read all four options. Eliminate choices with wrong units, sign or formula. Select the option matching NIOS textbook/PYQ.
NIOS marking: NIOS awards 1 mark all-or-nothing for the correct option. No partial marking in Section A MCQ.
Example: Example: F = ma with m = 2 kg, a = 3 m·s⁻² → F = 6 N (not 5 N or 6 kg).
Common mistakes: Picking a plausible but wrong formula; unit mismatch; confusing similar laws (e.g. Lenz vs Fleming).
Model answer: U_s = ½kx² = ½ × 100 × 0.04 = 2 J.
Q3. Torricelli's law gives speed of efflux from a tank as:
How to approach: Read all four options. Eliminate choices with wrong units, sign or formula. Select the option matching NIOS textbook/PYQ.
NIOS marking: NIOS awards 1 mark all-or-nothing for the correct option. No partial marking in Section A MCQ.
Example: Example: F = ma with m = 2 kg, a = 3 m·s⁻² → F = 6 N (not 5 N or 6 kg).
Common mistakes: Picking a plausible but wrong formula; unit mismatch; confusing similar laws (e.g. Lenz vs Fleming).
Model answer: v = √(2gH) where H is depth of hole below free surface.
Q4. In an adiabatic process for an ideal gas:
How to approach: Read all four options. Eliminate choices with wrong units, sign or formula. Select the option matching NIOS textbook/PYQ.
NIOS marking: NIOS awards 1 mark all-or-nothing for the correct option. No partial marking in Section A MCQ.
Example: Example: F = ma with m = 2 kg, a = 3 m·s⁻² → F = 6 N (not 5 N or 6 kg).
Common mistakes: Picking a plausible but wrong formula; unit mismatch; confusing similar laws (e.g. Lenz vs Fleming).
Model answer: Adiabatic: no heat exchange with surroundings, ΔQ = 0.
Q5. The phase difference between two points separated by λ/4 is:
How to approach: Read all four options. Eliminate choices with wrong units, sign or formula. Select the option matching NIOS textbook/PYQ.
NIOS marking: NIOS awards 1 mark all-or-nothing for the correct option. No partial marking in Section A MCQ.
Example: Example: F = ma with m = 2 kg, a = 3 m·s⁻² → F = 6 N (not 5 N or 6 kg).
Common mistakes: Picking a plausible but wrong formula; unit mismatch; confusing similar laws (e.g. Lenz vs Fleming).
Model answer: Phase change = (path difference/λ) × 2π = (λ/4/λ) × 2π = π/2 rad.
Q6. Two equal like charges are brought closer. Electrostatic potential energy of the system:
How to approach: Read all four options. Eliminate choices with wrong units, sign or formula. Select the option matching NIOS textbook/PYQ.
NIOS marking: NIOS awards 1 mark all-or-nothing for the correct option. No partial marking in Section A MCQ.
Example: Example: F = ma with m = 2 kg, a = 3 m·s⁻² → F = 6 N (not 5 N or 6 kg).
Common mistakes: Picking a plausible but wrong formula; unit mismatch; confusing similar laws (e.g. Lenz vs Fleming).
Model answer: Work done against repulsion is positive — stored PE increases as separation decreases.
Q7. If plate separation of a parallel-plate capacitor is doubled (area constant), capacitance:
How to approach: Read all four options. Eliminate choices with wrong units, sign or formula. Select the option matching NIOS textbook/PYQ.
NIOS marking: NIOS awards 1 mark all-or-nothing for the correct option. No partial marking in Section A MCQ.
Example: Example: F = ma with m = 2 kg, a = 3 m·s⁻² → F = 6 N (not 5 N or 6 kg).
Common mistakes: Picking a plausible but wrong formula; unit mismatch; confusing similar laws (e.g. Lenz vs Fleming).
Model answer: C = ε₀A/d — C ∝ 1/d, so capacitance halves.
Q8. Kirchhoff's junction rule is based on conservation of:
How to approach: Read all four options. Eliminate choices with wrong units, sign or formula. Select the option matching NIOS textbook/PYQ.
NIOS marking: NIOS awards 1 mark all-or-nothing for the correct option. No partial marking in Section A MCQ.
Example: Example: F = ma with m = 2 kg, a = 3 m·s⁻² → F = 6 N (not 5 N or 6 kg).
Common mistakes: Picking a plausible but wrong formula; unit mismatch; confusing similar laws (e.g. Lenz vs Fleming).
Model answer: ΣI_in = ΣI_out at junction — charge conservation, no accumulation at point.
Q9. The magnetic field at centre of a circular loop carrying current I (radius R) is:
How to approach: Read all four options. Eliminate choices with wrong units, sign or formula. Select the option matching NIOS textbook/PYQ.
NIOS marking: NIOS awards 1 mark all-or-nothing for the correct option. No partial marking in Section A MCQ.
Example: Example: F = ma with m = 2 kg, a = 3 m·s⁻² → F = 6 N (not 5 N or 6 kg).
Common mistakes: Picking a plausible but wrong formula; unit mismatch; confusing similar laws (e.g. Lenz vs Fleming).
Model answer: B = μ₀I/(2R) at centre of circular current loop.
Q10. In AC circuit, inductive reactance X_L equals:
How to approach: Read all four options. Eliminate choices with wrong units, sign or formula. Select the option matching NIOS textbook/PYQ.
NIOS marking: NIOS awards 1 mark all-or-nothing for the correct option. No partial marking in Section A MCQ.
Example: Example: F = ma with m = 2 kg, a = 3 m·s⁻² → F = 6 N (not 5 N or 6 kg).
Common mistakes: Picking a plausible but wrong formula; unit mismatch; confusing similar laws (e.g. Lenz vs Fleming).
Model answer: X_L = ωL — opposition to AC by inductor.
Q11. Rayleigh scattering explains blueness of sky because scattering intensity varies as:
How to approach: Read all four options. Eliminate choices with wrong units, sign or formula. Select the option matching NIOS textbook/PYQ.
NIOS marking: NIOS awards 1 mark all-or-nothing for the correct option. No partial marking in Section A MCQ.
Example: Example: F = ma with m = 2 kg, a = 3 m·s⁻² → F = 6 N (not 5 N or 6 kg).
Common mistakes: Picking a plausible but wrong formula; unit mismatch; confusing similar laws (e.g. Lenz vs Fleming).
Model answer: Intensity ∝ 1/λ⁴ — shorter blue wavelengths scatter more strongly.
Q12. Brewster's angle i_p satisfies:
How to approach: Read all four options. Eliminate choices with wrong units, sign or formula. Select the option matching NIOS textbook/PYQ.
NIOS marking: NIOS awards 1 mark all-or-nothing for the correct option. No partial marking in Section A MCQ.
Example: Example: F = ma with m = 2 kg, a = 3 m·s⁻² → F = 6 N (not 5 N or 6 kg).
Common mistakes: Picking a plausible but wrong formula; unit mismatch; confusing similar laws (e.g. Lenz vs Fleming).
Model answer: tan i_p = μ — at Brewster angle reflected ray is plane-polarised.
Q13. Maximum number of electrons in M-shell (n = 3) is:
How to approach: Read all four options. Eliminate choices with wrong units, sign or formula. Select the option matching NIOS textbook/PYQ.
NIOS marking: NIOS awards 1 mark all-or-nothing for the correct option. No partial marking in Section A MCQ.
Example: Example: F = ma with m = 2 kg, a = 3 m·s⁻² → F = 6 N (not 5 N or 6 kg).
Common mistakes: Picking a plausible but wrong formula; unit mismatch; confusing similar laws (e.g. Lenz vs Fleming).
Model answer: Maximum 2n² = 2×9 = 18 electrons in n = 3 shell.
Q14. In photoelectric effect, stopping potential depends on:
How to approach: Read all four options. Eliminate choices with wrong units, sign or formula. Select the option matching NIOS textbook/PYQ.
NIOS marking: NIOS awards 1 mark all-or-nothing for the correct option. No partial marking in Section A MCQ.
Example: Example: F = ma with m = 2 kg, a = 3 m·s⁻² → F = 6 N (not 5 N or 6 kg).
Common mistakes: Picking a plausible but wrong formula; unit mismatch; confusing similar laws (e.g. Lenz vs Fleming).
Model answer: eV_s = hν − φ₀ — stopping potential set by frequency, not intensity.
Q15. β-decay converts a neutron in nucleus to:
How to approach: Read all four options. Eliminate choices with wrong units, sign or formula. Select the option matching NIOS textbook/PYQ.
NIOS marking: NIOS awards 1 mark all-or-nothing for the correct option. No partial marking in Section A MCQ.
Example: Example: F = ma with m = 2 kg, a = 3 m·s⁻² → F = 6 N (not 5 N or 6 kg).
Common mistakes: Picking a plausible but wrong formula; unit mismatch; confusing similar laws (e.g. Lenz vs Fleming).
Model answer: n → p + e⁻ + ν̄ (beta-minus decay).
Q16. Critical mass in fission refers to:
How to approach: Read all four options. Eliminate choices with wrong units, sign or formula. Select the option matching NIOS textbook/PYQ.
NIOS marking: NIOS awards 1 mark all-or-nothing for the correct option. No partial marking in Section A MCQ.
Example: Example: F = ma with m = 2 kg, a = 3 m·s⁻² → F = 6 N (not 5 N or 6 kg).
Common mistakes: Picking a plausible but wrong formula; unit mismatch; confusing similar laws (e.g. Lenz vs Fleming).
Model answer: Below critical mass too many neutrons escape — chain reaction not sustained.
Q17. What is a hole in a semiconductor? Which type of doping increases hole concentration? (25–35 words.)
Suggested length: up to 30 words · 2 marks
0 / 30 words
How to approach: Answer in 25–35 words. For numerical/fill items: state formula, substitute values, give final answer with units.
NIOS marking: 2 marks = 2 sub-parts × 1 mark each — correct formula/match (1) + correct value/term (1).
Example: Example: P = ρgh → P = 1000×10×2 = 2×10⁴ Pa.
Common mistakes: Formula without value; value without units; exceeding word limit; vague one-word answers.
Model answer: Hole is vacancy left when covalent bond loses electron — acts as positive charge carrier. Trivalent acceptor doping (p-type, e.g. boron in Si) increases hole concentration.
Q18. Name two applications of Zener diode. What property is used in voltage regulation? (25–35 words.)
Suggested length: up to 30 words · 2 marks
0 / 30 words
How to approach: Answer in 25–35 words. For numerical/fill items: state formula, substitute values, give final answer with units.
NIOS marking: 2 marks = 2 sub-parts × 1 mark each — correct formula/match (1) + correct value/term (1).
Example: Example: P = ρgh → P = 1000×10×2 = 2×10⁴ Pa.
Common mistakes: Formula without value; value without units; exceeding word limit; vague one-word answers.
Model answer: Voltage regulation and reference voltage supply. Zener operates in reverse breakdown — maintains nearly constant voltage over a range of current (sharp breakdown characteristic).
Q19. Distinguish static and kinetic friction. Which is generally larger for same surfaces? (25–35 words.)
Suggested length: up to 30 words · 2 marks
0 / 30 words
How to approach: Answer in 25–35 words. For numerical/fill items: state formula, substitute values, give final answer with units.
NIOS marking: 2 marks = 2 sub-parts × 1 mark each — correct formula/match (1) + correct value/term (1).
Example: Example: P = ρgh → P = 1000×10×2 = 2×10⁴ Pa.
Common mistakes: Formula without value; value without units; exceeding word limit; vague one-word answers.
Model answer: Static friction acts when body at rest, opposes impending motion; kinetic friction acts during sliding. Limiting static friction is generally greater than kinetic friction for same pair of surfaces.
Q20. Define power. A motor lifts 100 kg by 2 m in 4 s (g = 10 m·s⁻²). Find average power. (25–35 words.)
Suggested length: up to 35 words · 2 marks
0 / 35 words
How to approach: Answer in 25–35 words. For numerical/fill items: state formula, substitute values, give final answer with units.
NIOS marking: 2 marks = 2 sub-parts × 1 mark each — correct formula/match (1) + correct value/term (1).
Example: Example: P = ρgh → P = 1000×10×2 = 2×10⁴ Pa.
Common mistakes: Formula without value; value without units; exceeding word limit; vague one-word answers.
Model answer: Power = work/time. W = mgh = 100×10×2 = 2000 J. P = W/t = 2000/4 = 500 W.
Q21. State Pascal's law. A force 50 N on piston area 5 cm² transmits to area 250 cm². Find output force. (25–35 words.)
Suggested length: up to 35 words · 2 marks
0 / 35 words
How to approach: Answer in 25–35 words. For numerical/fill items: state formula, substitute values, give final answer with units.
NIOS marking: 2 marks = 2 sub-parts × 1 mark each — correct formula/match (1) + correct value/term (1).
Example: Example: P = ρgh → P = 1000×10×2 = 2×10⁴ Pa.
Common mistakes: Formula without value; value without units; exceeding word limit; vague one-word answers.
Model answer: Pressure applied to enclosed fluid transmits undiminished. F₂ = F₁ × A₂/A₁ = 50 × 250/5 = 2500 N.
Q22. Define coefficient of performance (COP) of refrigerator. Can COP exceed 1? (25–35 words.)
Suggested length: up to 30 words · 2 marks
0 / 30 words
How to approach: Answer in 25–35 words. For numerical/fill items: state formula, substitute values, give final answer with units.
NIOS marking: 2 marks = 2 sub-parts × 1 mark each — correct formula/match (1) + correct value/term (1).
Example: Example: P = ρgh → P = 1000×10×2 = 2×10⁴ Pa.
Common mistakes: Formula without value; value without units; exceeding word limit; vague one-word answers.
Model answer: COP = heat removed from cold reservoir / work input = Q₂/W. Yes, COP can exceed 1 — heat transferred exceeds work supplied (not efficiency of engine).
Q23. A tuning fork vibrates at 512 Hz. Calculate wavelength in air if v = 340 m·s⁻¹. (25–35 words.)
Suggested length: up to 35 words · 2 marks
0 / 35 words
How to approach: Answer in 25–35 words. For numerical/fill items: state formula, substitute values, give final answer with units.
NIOS marking: 2 marks = 2 sub-parts × 1 mark each — correct formula/match (1) + correct value/term (1).
Example: Example: P = ρgh → P = 1000×10×2 = 2×10⁴ Pa.
Common mistakes: Formula without value; value without units; exceeding word limit; vague one-word answers.
Model answer: λ = v/f = 340/512 ≈ 0.66 m. Sound speed in air at room temperature ≈ 340 m·s⁻¹.
Q24. Define electric dipole moment. Write its SI unit. (25–35 words.)
Suggested length: up to 30 words · 2 marks
0 / 30 words
How to approach: Answer in 25–35 words. For numerical/fill items: state formula, substitute values, give final answer with units.
NIOS marking: 2 marks = 2 sub-parts × 1 mark each — correct formula/match (1) + correct value/term (1).
Example: Example: P = ρgh → P = 1000×10×2 = 2×10⁴ Pa.
Common mistakes: Formula without value; value without units; exceeding word limit; vague one-word answers.
Model answer: p = q × 2a — product of magnitude of either charge and separation between charges. SI unit: C·m (coulomb-metre).
Q25. Three capacitors 2 μF each are connected in parallel. Find equivalent capacitance. (25–35 words.)
Suggested length: up to 30 words · 2 marks
0 / 30 words
How to approach: Answer in 25–35 words. For numerical/fill items: state formula, substitute values, give final answer with units.
NIOS marking: 2 marks = 2 sub-parts × 1 mark each — correct formula/match (1) + correct value/term (1).
Example: Example: P = ρgh → P = 1000×10×2 = 2×10⁴ Pa.
Common mistakes: Formula without value; value without units; exceeding word limit; vague one-word answers.
Model answer: Parallel: C_eq = C₁ + C₂ + C₃ = 2 + 2 + 2 = 6 μF. Same voltage across each; charges add.
Q26. In balanced Wheatstone bridge P = 10 Ω, Q = 5 Ω, R = 8 Ω. Find S. (25–35 words.)
Suggested length: up to 35 words · 2 marks
0 / 35 words
How to approach: Answer in 25–35 words. For numerical/fill items: state formula, substitute values, give final answer with units.
NIOS marking: 2 marks = 2 sub-parts × 1 mark each — correct formula/match (1) + correct value/term (1).
Example: Example: P = ρgh → P = 1000×10×2 = 2×10⁴ Pa.
Common mistakes: Formula without value; value without units; exceeding word limit; vague one-word answers.
Model answer: P/Q = R/S → 10/5 = 8/S → S = 4 Ω. At balance galvanometer shows zero deflection.
Q27. State properties of magnetic field lines. Do they form closed loops? (25–35 words.)
Suggested length: up to 30 words · 2 marks
0 / 30 words
How to approach: Answer in 25–35 words. For numerical/fill items: state formula, substitute values, give final answer with units.
NIOS marking: 2 marks = 2 sub-parts × 1 mark each — correct formula/match (1) + correct value/term (1).
Example: Example: P = ρgh → P = 1000×10×2 = 2×10⁴ Pa.
Common mistakes: Formula without value; value without units; exceeding word limit; vague one-word answers.
Model answer: Field lines are continuous closed curves (no magnetic monopoles). Tangent gives B direction; density indicates field strength; lines never cross.
Q28. Write transformer equation relating voltages to turns. If N_p:N_s = 1:10 and V_p = 220 V, find V_s. (25–35 words.)
Suggested length: up to 35 words · 2 marks
0 / 35 words
How to approach: Answer in 25–35 words. For numerical/fill items: state formula, substitute values, give final answer with units.
NIOS marking: 2 marks = 2 sub-parts × 1 mark each — correct formula/match (1) + correct value/term (1).
Example: Example: P = ρgh → P = 1000×10×2 = 2×10⁴ Pa.
Common mistakes: Formula without value; value without units; exceeding word limit; vague one-word answers.
Model answer: V_s/V_p = N_s/N_p. With ratio 10:1, V_s = 220 × 10 = 2200 V (step-up transformer).
Q29. What is angular dispersion in a prism? How does it depend on refractive index? (30–50 words.)
Suggested length: up to 45 words · 2 marks
0 / 45 words
How to approach: Write 30–50 words. Open with the law/formula/name, then one-line explanation or numerical step.
NIOS marking: 2 marks = correct law/formula (1) + brief explanation/application (1).
Example: Example: Lenz's law — induced current opposes the change in magnetic flux causing it.
Common mistakes: Long derivation; missing law statement; wrong units; copying notes without answering the question.
Model answer: Angular dispersion is difference in deviation between extreme colours (δ_v − δ_r). Since μ varies with λ, violet (higher μ) deviates more — spectrum spreads.
Q30. State conditions for sustained interference fringes. What is coherent source? (30–50 words.)
Suggested length: up to 45 words · 2 marks
0 / 45 words
How to approach: Write 30–50 words. Open with the law/formula/name, then one-line explanation or numerical step.
NIOS marking: 2 marks = correct law/formula (1) + brief explanation/application (1).
Example: Example: Lenz's law — induced current opposes the change in magnetic flux causing it.
Common mistakes: Long derivation; missing law statement; wrong units; copying notes without answering the question.
Model answer: Sources must be coherent — constant phase difference, same frequency (monochromatic). Superposition of waves from such sources gives stable alternate bright and dark fringes.
Q31. Write three postulates of Bohr model. Why are orbits called stationary? (30–50 words.)
Suggested length: up to 50 words · 2 marks
0 / 50 words
How to approach: Write 30–50 words. Open with the law/formula/name, then one-line explanation or numerical step.
NIOS marking: 2 marks = correct law/formula (1) + brief explanation/application (1).
Example: Example: Lenz's law — induced current opposes the change in magnetic flux causing it.
Common mistakes: Long derivation; missing law statement; wrong units; copying notes without answering the question.
Model answer: Electrons in certain orbits; angular momentum quantised (mvr = nh/2π); radiation only on transitions. Stationary orbits — no energy radiation while electron remains in allowed orbit.
Q32. State two experimental facts explained by photoelectric effect but not wave theory. (30–50 words.)
Suggested length: up to 45 words · 2 marks
0 / 45 words
How to approach: Write 30–50 words. Open with the law/formula/name, then one-line explanation or numerical step.
NIOS marking: 2 marks = correct law/formula (1) + brief explanation/application (1).
Example: Example: Lenz's law — induced current opposes the change in magnetic flux causing it.
Common mistakes: Long derivation; missing law statement; wrong units; copying notes without answering the question.
Model answer: Emission occurs only if frequency exceeds threshold (hν > φ₀) — independent of intensity. Photoelectrons emitted almost instantaneously — supports quantum photon model.
Q33. Define activity of radioactive sample. Write relation between activity and decay constant. (30–50 words.)
Suggested length: up to 45 words · 2 marks
0 / 45 words
How to approach: Write 30–50 words. Open with the law/formula/name, then one-line explanation or numerical step.
NIOS marking: 2 marks = correct law/formula (1) + brief explanation/application (1).
Example: Example: Lenz's law — induced current opposes the change in magnetic flux causing it.
Common mistakes: Long derivation; missing law statement; wrong units; copying notes without answering the question.
Model answer: Activity A = rate of disintegration (decays per second); unit Bq. A = λN where λ is decay constant and N is number of undecayed nuclei at that instant.
Q34. Compare fission and fusion on fuel, products and energy per event. (30–50 words.)
Suggested length: up to 50 words · 2 marks
0 / 50 words
How to approach: Write 30–50 words. Open with the law/formula/name, then one-line explanation or numerical step.
NIOS marking: 2 marks = correct law/formula (1) + brief explanation/application (1).
Example: Example: Lenz's law — induced current opposes the change in magnetic flux causing it.
Common mistakes: Long derivation; missing law statement; wrong units; copying notes without answering the question.
Model answer: Fission splits heavy nuclei (²³⁵U) — ~200 MeV/event, radioactive products. Fusion combines light nuclei (²H) — ~24 MeV/event, cleaner products, abundant fuel (deuterium).
Q35. Explain forward and reverse bias of p-n junction with barrier height change. (30–50 words.)
Suggested length: up to 50 words · 2 marks
0 / 50 words
How to approach: Write 30–50 words. Open with the law/formula/name, then one-line explanation or numerical step.
NIOS marking: 2 marks = correct law/formula (1) + brief explanation/application (1).
Example: Example: Lenz's law — induced current opposes the change in magnetic flux causing it.
Common mistakes: Long derivation; missing law statement; wrong units; copying notes without answering the question.
Model answer: Forward: p to +ve, n to −ve — barrier lowers, depletion layer narrows, large forward current. Reverse: opposite polarity — barrier rises, layer widens, negligible current.
Q36. How does a transistor work as an amplifier in CE configuration? Name three terminals. (30–50 words.)
Suggested length: up to 50 words · 2 marks
0 / 50 words
How to approach: Write 30–50 words. Open with the law/formula/name, then one-line explanation or numerical step.
NIOS marking: 2 marks = correct law/formula (1) + brief explanation/application (1).
Example: Example: Lenz's law — induced current opposes the change in magnetic flux causing it.
Common mistakes: Long derivation; missing law statement; wrong units; copying notes without answering the question.
Model answer: Small base current controls larger collector current (I_C = βI_B). Terminals: emitter, base, collector. CE configuration gives voltage and current gain for amplification.
Q37. Explain why a passenger lurches forward when a bus stops suddenly. Which law applies? (30–50 words.)
Suggested length: up to 45 words · 2 marks
0 / 45 words
How to approach: Write 30–50 words. Open with the law/formula/name, then one-line explanation or numerical step.
NIOS marking: 2 marks = correct law/formula (1) + brief explanation/application (1).
Example: Example: Lenz's law — induced current opposes the change in magnetic flux causing it.
Common mistakes: Long derivation; missing law statement; wrong units; copying notes without answering the question.
Model answer: Body tends to continue uniform motion (Newton's first law — inertia). Lower body stops with bus but upper body tends to keep moving forward — passenger lurches.
Q38. A 1500 kg car brakes from 20 m·s⁻¹ to 5 m·s⁻¹. Find change in KE and work done by brakes. (50–80 words.)
Suggested length: up to 75 words · 3 marks
0 / 75 words
How to approach: Structure: formula/diagram (1) → substitution/working (1) → final answer with units (1). Use 50–80 words.
NIOS marking: 3 marks = formula or labelled diagram (1) + correct working (1) + answer with units (1).
Example: Example: W = mgh = 5×10×2 = 100 J work done against gravity.
Common mistakes: Skipping working; missing units; wrong sign convention; diagram without labels.
Model answer: K_i = ½×1500×400 = 300 000 J; K_f = ½×1500×25 = 18 750 J. ΔK = −281 250 J. Work by brakes = ΔK = −281 250 J (energy removed).
Q39. A wooden block (ρ = 600 kg·m⁻³) of volume 0.005 m³ floats in water (ρ_w = 1000 kg·m⁻³). Find submerged volume. (50–80 words.)
Suggested length: up to 75 words · 3 marks
0 / 75 words
How to approach: Structure: formula/diagram (1) → substitution/working (1) → final answer with units (1). Use 50–80 words.
NIOS marking: 3 marks = formula or labelled diagram (1) + correct working (1) + answer with units (1).
Example: Example: W = mgh = 5×10×2 = 100 J work done against gravity.
Common mistakes: Skipping working; missing units; wrong sign convention; diagram without labels.
Model answer: Weight = 600×0.005×10 = 30 N. Floating: buoyant = weight. V_sub = 30/(1000×10) = 0.003 m³. Fraction submerged = 0.003/0.005 = 0.60.
Q40. Define entropy. State second law of thermodynamics for an isolated system. (50–80 words.)
Suggested length: up to 75 words · 3 marks
0 / 75 words
How to approach: Structure: formula/diagram (1) → substitution/working (1) → final answer with units (1). Use 50–80 words.
NIOS marking: 3 marks = formula or labelled diagram (1) + correct working (1) + answer with units (1).
Example: Example: W = mgh = 5×10×2 = 100 J work done against gravity.
Common mistakes: Skipping working; missing units; wrong sign convention; diagram without labels.
Model answer: Entropy S measures disorder/unavailable energy. Second law: total entropy of an isolated system never decreases — natural processes tend toward maximum entropy; heat flows spontaneously hot to cold.
Q41. A coil of 200 turns, area 0.01 m², rotates at 50 rev·s⁻¹ in B = 0.1 T. Find maximum emf (ε₀ = NBAω). (50–80 words.)
Suggested length: up to 80 words · 3 marks
0 / 80 words
How to approach: Structure: formula/diagram (1) → substitution/working (1) → final answer with units (1). Use 50–80 words.
NIOS marking: 3 marks = formula or labelled diagram (1) + correct working (1) + answer with units (1).
Example: Example: W = mgh = 5×10×2 = 100 J work done against gravity.
Common mistakes: Skipping working; missing units; wrong sign convention; diagram without labels.
Model answer: ω = 2π × 50 = 100π rad·s⁻¹. ε₀ = NBAω = 200 × 0.1 × 0.01 × 100π = 20π ≈ 62.8 V. Alternating emf varies as sin ωt.
Q42. Define capacitance. Derive expression for parallel-plate capacitor C = ε₀A/d. Explain energy stored U = ½CV². (80–120 words.)
Suggested length: up to 110 words · 5 marks
0 / 110 words
How to approach: Plan 80–120 words: state law/principle (1) → formula/diagram (1) → derivation or worked example (2) → conclusion (1).
NIOS marking: 5 marks = statement of law (1) + diagram/formula (1) + derivation/working (2) + conclusion with units (1).
Example: Example: State Gauss's law, draw Gaussian surface, derive E = σ/(2ε₀) for infinite sheet, note direction.
Common mistakes: Only definition without working; no diagram where required; arithmetic errors; missing conclusion.
Model answer: Capacitance C = Q/V — charge stored per unit potential. Uniform field E = V/d, flux Φ = EA, using C = Q/V and Q = ε₀EA gives C = ε₀A/d. Charging transfers charge from −ve to +ve plate storing energy in field; U = ½CV² = ½QV (work done against field).
Q43. Describe photoelectric effect experimental setup. State Einstein's photoelectric equation and explain threshold frequency. (80–120 words.)
Suggested length: up to 115 words · 5 marks
0 / 115 words
How to approach: Plan 80–120 words: state law/principle (1) → formula/diagram (1) → derivation or worked example (2) → conclusion (1).
NIOS marking: 5 marks = statement of law (1) + diagram/formula (1) + derivation/working (2) + conclusion with units (1).
Example: Example: State Gauss's law, draw Gaussian surface, derive E = σ/(2ε₀) for infinite sheet, note direction.
Common mistakes: Only definition without working; no diagram where required; arithmetic errors; missing conclusion.
Model answer: Light of frequency ν falls on photosensitive cathode; photoelectrons ejected, collected by anode — current measured. Einstein: hν = φ₀ + K_max — photon energy equals work function plus maximum KE. Threshold frequency ν₀ = φ₀/h — below ν₀ no emission however intense light; supports photon theory over classical wave model.
Q1. A 60 kg person stands in a lift accelerating upward at 2 m·s⁻² (g = 10 m·s⁻²). Normal reaction on person is:
How to approach: Read all four options. Eliminate choices with wrong units, sign or formula. Select the option matching NIOS textbook/PYQ.
NIOS marking: NIOS awards 1 mark all-or-nothing for the correct option. No partial marking in Section A MCQ.
Example: Example: F = ma with m = 2 kg, a = 3 m·s⁻² → F = 6 N (not 5 N or 6 kg).
Common mistakes: Picking a plausible but wrong formula; unit mismatch; confusing similar laws (e.g. Lenz vs Fleming).
Model answer: N − mg = ma → N = m(g + a) = 60 × 12 = 720 N.
Q2. Which force is non-conservative?
How to approach: Read all four options. Eliminate choices with wrong units, sign or formula. Select the option matching NIOS textbook/PYQ.
NIOS marking: NIOS awards 1 mark all-or-nothing for the correct option. No partial marking in Section A MCQ.
Example: Example: F = ma with m = 2 kg, a = 3 m·s⁻² → F = 6 N (not 5 N or 6 kg).
Common mistakes: Picking a plausible but wrong formula; unit mismatch; confusing similar laws (e.g. Lenz vs Fleming).
Model answer: Kinetic friction dissipates mechanical energy as heat — path dependent, non-conservative.
Q3. Gauge pressure at depth h in liquid of density ρ is:
How to approach: Read all four options. Eliminate choices with wrong units, sign or formula. Select the option matching NIOS textbook/PYQ.
NIOS marking: NIOS awards 1 mark all-or-nothing for the correct option. No partial marking in Section A MCQ.
Example: Example: F = ma with m = 2 kg, a = 3 m·s⁻² → F = 6 N (not 5 N or 6 kg).
Common mistakes: Picking a plausible but wrong formula; unit mismatch; confusing similar laws (e.g. Lenz vs Fleming).
Model answer: Gauge pressure (above atmospheric) = ρgh.
Q4. In isothermal expansion of ideal gas:
How to approach: Read all four options. Eliminate choices with wrong units, sign or formula. Select the option matching NIOS textbook/PYQ.
NIOS marking: NIOS awards 1 mark all-or-nothing for the correct option. No partial marking in Section A MCQ.
Example: Example: F = ma with m = 2 kg, a = 3 m·s⁻² → F = 6 N (not 5 N or 6 kg).
Common mistakes: Picking a plausible but wrong formula; unit mismatch; confusing similar laws (e.g. Lenz vs Fleming).
Model answer: Isothermal: T constant → internal energy of ideal gas unchanged, ΔU = 0.
Q5. Speed of transverse wave on a stretched string increases when:
How to approach: Read all four options. Eliminate choices with wrong units, sign or formula. Select the option matching NIOS textbook/PYQ.
NIOS marking: NIOS awards 1 mark all-or-nothing for the correct option. No partial marking in Section A MCQ.
Example: Example: F = ma with m = 2 kg, a = 3 m·s⁻² → F = 6 N (not 5 N or 6 kg).
Common mistakes: Picking a plausible but wrong formula; unit mismatch; confusing similar laws (e.g. Lenz vs Fleming).
Model answer: v = √(T/μ) — speed increases with tension T, decreases with μ.
Q6. Electric potential at a point is:
How to approach: Read all four options. Eliminate choices with wrong units, sign or formula. Select the option matching NIOS textbook/PYQ.
NIOS marking: NIOS awards 1 mark all-or-nothing for the correct option. No partial marking in Section A MCQ.
Example: Example: F = ma with m = 2 kg, a = 3 m·s⁻² → F = 6 N (not 5 N or 6 kg).
Common mistakes: Picking a plausible but wrong formula; unit mismatch; confusing similar laws (e.g. Lenz vs Fleming).
Model answer: V = W/q₀ — work per unit positive test charge from infinity to point.
Q7. When a dielectric is inserted between capacitor plates (battery connected), charge on plates:
How to approach: Read all four options. Eliminate choices with wrong units, sign or formula. Select the option matching NIOS textbook/PYQ.
NIOS marking: NIOS awards 1 mark all-or-nothing for the correct option. No partial marking in Section A MCQ.
Example: Example: F = ma with m = 2 kg, a = 3 m·s⁻² → F = 6 N (not 5 N or 6 kg).
Common mistakes: Picking a plausible but wrong formula; unit mismatch; confusing similar laws (e.g. Lenz vs Fleming).
Model answer: V fixed by battery; C increases with dielectric (C = κC₀) → Q = CV increases.
Q8. Resistivity of a conductor depends on:
How to approach: Read all four options. Eliminate choices with wrong units, sign or formula. Select the option matching NIOS textbook/PYQ.
NIOS marking: NIOS awards 1 mark all-or-nothing for the correct option. No partial marking in Section A MCQ.
Example: Example: F = ma with m = 2 kg, a = 3 m·s⁻² → F = 6 N (not 5 N or 6 kg).
Common mistakes: Picking a plausible but wrong formula; unit mismatch; confusing similar laws (e.g. Lenz vs Fleming).
Model answer: ρ is material property; varies with temperature — not geometry.
Q9. Ampere's circuital law relates line integral of B around closed loop to:
How to approach: Read all four options. Eliminate choices with wrong units, sign or formula. Select the option matching NIOS textbook/PYQ.
NIOS marking: NIOS awards 1 mark all-or-nothing for the correct option. No partial marking in Section A MCQ.
Example: Example: F = ma with m = 2 kg, a = 3 m·s⁻² → F = 6 N (not 5 N or 6 kg).
Common mistakes: Picking a plausible but wrong formula; unit mismatch; confusing similar laws (e.g. Lenz vs Fleming).
Model answer: ∮B·dl = μ₀ I_enclosed — circulation of B linked to net current through loop.
Q10. Motional emf induced in rod of length l moving at speed v perpendicular to B is:
How to approach: Read all four options. Eliminate choices with wrong units, sign or formula. Select the option matching NIOS textbook/PYQ.
NIOS marking: NIOS awards 1 mark all-or-nothing for the correct option. No partial marking in Section A MCQ.
Example: Example: F = ma with m = 2 kg, a = 3 m·s⁻² → F = 6 N (not 5 N or 6 kg).
Common mistakes: Picking a plausible but wrong formula; unit mismatch; confusing similar laws (e.g. Lenz vs Fleming).
Model answer: ε = Blv when B, v and l mutually perpendicular (flux change).
Q11. Rainbow formation in sky involves:
How to approach: Read all four options. Eliminate choices with wrong units, sign or formula. Select the option matching NIOS textbook/PYQ.
NIOS marking: NIOS awards 1 mark all-or-nothing for the correct option. No partial marking in Section A MCQ.
Example: Example: F = ma with m = 2 kg, a = 3 m·s⁻² → F = 6 N (not 5 N or 6 kg).
Common mistakes: Picking a plausible but wrong formula; unit mismatch; confusing similar laws (e.g. Lenz vs Fleming).
Model answer: Dispersion splits sunlight; total internal reflection in droplets; observer sees rainbow.
Q12. In single-slit diffraction, central maximum is:
How to approach: Read all four options. Eliminate choices with wrong units, sign or formula. Select the option matching NIOS textbook/PYQ.
NIOS marking: NIOS awards 1 mark all-or-nothing for the correct option. No partial marking in Section A MCQ.
Example: Example: F = ma with m = 2 kg, a = 3 m·s⁻² → F = 6 N (not 5 N or 6 kg).
Common mistakes: Picking a plausible but wrong formula; unit mismatch; confusing similar laws (e.g. Lenz vs Fleming).
Model answer: Central maximum contains most intensity and is twice as wide as secondary maxima.
Q13. Hydrogen spectral line at 656 nm belongs to:
How to approach: Read all four options. Eliminate choices with wrong units, sign or formula. Select the option matching NIOS textbook/PYQ.
NIOS marking: NIOS awards 1 mark all-or-nothing for the correct option. No partial marking in Section A MCQ.
Example: Example: F = ma with m = 2 kg, a = 3 m·s⁻² → F = 6 N (not 5 N or 6 kg).
Common mistakes: Picking a plausible but wrong formula; unit mismatch; confusing similar laws (e.g. Lenz vs Fleming).
Model answer: 656 nm red line — Balmer series (transitions to n = 2).
Q14. de Broglie wavelength of electron accelerated through 400 V is approximately:
How to approach: Read all four options. Eliminate choices with wrong units, sign or formula. Select the option matching NIOS textbook/PYQ.
NIOS marking: NIOS awards 1 mark all-or-nothing for the correct option. No partial marking in Section A MCQ.
Example: Example: F = ma with m = 2 kg, a = 3 m·s⁻² → F = 6 N (not 5 N or 6 kg).
Common mistakes: Picking a plausible but wrong formula; unit mismatch; confusing similar laws (e.g. Lenz vs Fleming).
Model answer: λ = 12.3/√V Å = 12.3/20 = 0.615 Å.
Q15. Binding energy per nucleon is maximum near:
How to approach: Read all four options. Eliminate choices with wrong units, sign or formula. Select the option matching NIOS textbook/PYQ.
NIOS marking: NIOS awards 1 mark all-or-nothing for the correct option. No partial marking in Section A MCQ.
Example: Example: F = ma with m = 2 kg, a = 3 m·s⁻² → F = 6 N (not 5 N or 6 kg).
Common mistakes: Picking a plausible but wrong formula; unit mismatch; confusing similar laws (e.g. Lenz vs Fleming).
Model answer: B/A curve peaks near iron-56 (~8.8 MeV/nucleon) — most stable mid-mass nuclei.
Q16. Moderator in nuclear reactor is used to:
How to approach: Read all four options. Eliminate choices with wrong units, sign or formula. Select the option matching NIOS textbook/PYQ.
NIOS marking: NIOS awards 1 mark all-or-nothing for the correct option. No partial marking in Section A MCQ.
Example: Example: F = ma with m = 2 kg, a = 3 m·s⁻² → F = 6 N (not 5 N or 6 kg).
Common mistakes: Picking a plausible but wrong formula; unit mismatch; confusing similar laws (e.g. Lenz vs Fleming).
Model answer: Moderator (e.g. heavy water, graphite) slows fast fission neutrons for efficient further fission.
Q17. What is energy band gap in semiconductor? Compare with conductor and insulator. (25–35 words.)
Suggested length: up to 35 words · 2 marks
0 / 35 words
How to approach: Answer in 25–35 words. For numerical/fill items: state formula, substitute values, give final answer with units.
NIOS marking: 2 marks = 2 sub-parts × 1 mark each — correct formula/match (1) + correct value/term (1).
Example: Example: P = ρgh → P = 1000×10×2 = 2×10⁴ Pa.
Common mistakes: Formula without value; value without units; exceeding word limit; vague one-word answers.
Model answer: Gap between valence and conduction bands. Conductor: overlapping/partially filled bands; insulator: large gap (~5 eV); semiconductor: small gap (~1 eV) — excitation at room temperature.
Q18. What is a rectifier? Name one semiconductor device used for half-wave rectification. (25–35 words.)
Suggested length: up to 30 words · 2 marks
0 / 30 words
How to approach: Answer in 25–35 words. For numerical/fill items: state formula, substitute values, give final answer with units.
NIOS marking: 2 marks = 2 sub-parts × 1 mark each — correct formula/match (1) + correct value/term (1).
Example: Example: P = ρgh → P = 1000×10×2 = 2×10⁴ Pa.
Common mistakes: Formula without value; value without units; exceeding word limit; vague one-word answers.
Model answer: Rectifier converts AC to pulsating/DC. p-n junction diode allows current mainly in one direction — used in half-wave rectifier circuit.
Q19. State law of conservation of linear momentum. When is it valid? (25–35 words.)
Suggested length: up to 30 words · 2 marks
0 / 30 words
How to approach: Answer in 25–35 words. For numerical/fill items: state formula, substitute values, give final answer with units.
NIOS marking: 2 marks = 2 sub-parts × 1 mark each — correct formula/match (1) + correct value/term (1).
Example: Example: P = ρgh → P = 1000×10×2 = 2×10⁴ Pa.
Common mistakes: Formula without value; value without units; exceeding word limit; vague one-word answers.
Model answer: Total momentum of isolated system (no external net force) remains constant. Valid for collisions/explosions when external forces negligible during short interaction.
Q20. A 1 kg object falls freely from 5 m height (g = 10 m·s⁻²). Find PE lost and KE gained at ground. (25–35 words.)
Suggested length: up to 35 words · 2 marks
0 / 35 words
How to approach: Answer in 25–35 words. For numerical/fill items: state formula, substitute values, give final answer with units.
NIOS marking: 2 marks = 2 sub-parts × 1 mark each — correct formula/match (1) + correct value/term (1).
Example: Example: P = ρgh → P = 1000×10×2 = 2×10⁴ Pa.
Common mistakes: Formula without value; value without units; exceeding word limit; vague one-word answers.
Model answer: PE lost = mgh = 1×10×5 = 50 J. By conservation (no friction), KE gained = 50 J at ground; speed v = √(2gh) = 10 m·s⁻¹.
Q21. Define viscosity. How does temperature affect viscosity of liquids? (25–35 words.)
Suggested length: up to 30 words · 2 marks
0 / 30 words
How to approach: Answer in 25–35 words. For numerical/fill items: state formula, substitute values, give final answer with units.
NIOS marking: 2 marks = 2 sub-parts × 1 mark each — correct formula/match (1) + correct value/term (1).
Example: Example: P = ρgh → P = 1000×10×2 = 2×10⁴ Pa.
Common mistakes: Formula without value; value without units; exceeding word limit; vague one-word answers.
Model answer: Viscosity is internal friction opposing relative motion between fluid layers. For liquids, viscosity generally decreases as temperature rises — molecules move apart, flow easier.
Q22. A gas absorbs 400 J heat and does 250 J work. Find ΔU using first law. (25–35 words.)
Suggested length: up to 35 words · 2 marks
0 / 35 words
How to approach: Answer in 25–35 words. For numerical/fill items: state formula, substitute values, give final answer with units.
NIOS marking: 2 marks = 2 sub-parts × 1 mark each — correct formula/match (1) + correct value/term (1).
Example: Example: P = ρgh → P = 1000×10×2 = 2×10⁴ Pa.
Common mistakes: Formula without value; value without units; exceeding word limit; vague one-word answers.
Model answer: ΔQ = +400 J (to system), ΔW = +250 J (by system). ΔU = ΔQ − ΔW = 400 − 250 = 150 J increase in internal energy.
Q23. Distinguish transverse and longitudinal waves with one example each. (25–35 words.)
Suggested length: up to 30 words · 2 marks
0 / 30 words
How to approach: Answer in 25–35 words. For numerical/fill items: state formula, substitute values, give final answer with units.
NIOS marking: 2 marks = 2 sub-parts × 1 mark each — correct formula/match (1) + correct value/term (1).
Example: Example: P = ρgh → P = 1000×10×2 = 2×10⁴ Pa.
Common mistakes: Formula without value; value without units; exceeding word limit; vague one-word answers.
Model answer: Transverse: particle oscillation perpendicular to propagation (e.g. light on string). Longitudinal: oscillation parallel to propagation (e.g. sound in air).
Q24. Two point charges +2 μC and −2 μC are 0.1 m apart. What is net charge and type of dipole? (25–35 words.)
Suggested length: up to 35 words · 2 marks
0 / 35 words
How to approach: Answer in 25–35 words. For numerical/fill items: state formula, substitute values, give final answer with units.
NIOS marking: 2 marks = 2 sub-parts × 1 mark each — correct formula/match (1) + correct value/term (1).
Example: Example: P = ρgh → P = 1000×10×2 = 2×10⁴ Pa.
Common mistakes: Formula without value; value without units; exceeding word limit; vague one-word answers.
Model answer: Net charge = +2 + (−2) = 0. System is an electric dipole — equal and opposite charges separated by distance, nonzero dipole moment p = q × 2a.
Q25. A 5 μF capacitor is charged to 100 V. Find charge Q and energy stored. (25–35 words.)
Suggested length: up to 35 words · 2 marks
0 / 35 words
How to approach: Answer in 25–35 words. For numerical/fill items: state formula, substitute values, give final answer with units.
NIOS marking: 2 marks = 2 sub-parts × 1 mark each — correct formula/match (1) + correct value/term (1).
Example: Example: P = ρgh → P = 1000×10×2 = 2×10⁴ Pa.
Common mistakes: Formula without value; value without units; exceeding word limit; vague one-word answers.
Model answer: Q = CV = 5×10⁻⁶ × 100 = 5×10⁻⁴ C = 0.5 mC. U = ½CV² = ½ × 5×10⁻⁶ × 10⁴ = 0.025 J.
Q26. Three resistors 2 Ω, 3 Ω, 6 Ω are in parallel. Find equivalent resistance. (25–35 words.)
Suggested length: up to 35 words · 2 marks
0 / 35 words
How to approach: Answer in 25–35 words. For numerical/fill items: state formula, substitute values, give final answer with units.
NIOS marking: 2 marks = 2 sub-parts × 1 mark each — correct formula/match (1) + correct value/term (1).
Example: Example: P = ρgh → P = 1000×10×2 = 2×10⁴ Pa.
Common mistakes: Formula without value; value without units; exceeding word limit; vague one-word answers.
Model answer: 1/R_eq = 1/2 + 1/3 + 1/6 = 3/6 + 2/6 + 1/6 = 1 → R_eq = 1 Ω.
Q27. State right-hand thumb rule for straight current-carrying conductor. What does thumb represent? (25–35 words.)
Suggested length: up to 30 words · 2 marks
0 / 30 words
How to approach: Answer in 25–35 words. For numerical/fill items: state formula, substitute values, give final answer with units.
NIOS marking: 2 marks = 2 sub-parts × 1 mark each — correct formula/match (1) + correct value/term (1).
Example: Example: P = ρgh → P = 1000×10×2 = 2×10⁴ Pa.
Common mistakes: Formula without value; value without units; exceeding word limit; vague one-word answers.
Model answer: Grasp wire with right hand — thumb along current direction; curled fingers show direction of magnetic field lines around conductor.
Q28. Define rms value of AC current. If I₀ = 10 A, find I_rms. (25–35 words.)
Suggested length: up to 30 words · 2 marks
0 / 30 words
How to approach: Answer in 25–35 words. For numerical/fill items: state formula, substitute values, give final answer with units.
NIOS marking: 2 marks = 2 sub-parts × 1 mark each — correct formula/match (1) + correct value/term (1).
Example: Example: P = ρgh → P = 1000×10×2 = 2×10⁴ Pa.
Common mistakes: Formula without value; value without units; exceeding word limit; vague one-word answers.
Model answer: I_rms is effective DC equivalent producing same heating. I_rms = I₀/√2 = 10/√2 ≈ 7.07 A.
Q29. Why do clouds appear white while clear sky looks blue? (30–50 words.)
Suggested length: up to 45 words · 2 marks
0 / 45 words
How to approach: Write 30–50 words. Open with the law/formula/name, then one-line explanation or numerical step.
NIOS marking: 2 marks = correct law/formula (1) + brief explanation/application (1).
Example: Example: Lenz's law — induced current opposes the change in magnetic flux causing it.
Common mistakes: Long derivation; missing law statement; wrong units; copying notes without answering the question.
Model answer: Sky: selective Rayleigh scattering of shorter wavelengths. Cloud droplets are large compared to λ — scatter all wavelengths roughly equally → white appearance.
Q30. State Huygens' principle. How does it explain reflection of light? (30–50 words.)
Suggested length: up to 50 words · 2 marks
0 / 50 words
How to approach: Write 30–50 words. Open with the law/formula/name, then one-line explanation or numerical step.
NIOS marking: 2 marks = correct law/formula (1) + brief explanation/application (1).
Example: Example: Lenz's law — induced current opposes the change in magnetic flux causing it.
Common mistakes: Long derivation; missing law statement; wrong units; copying notes without answering the question.
Model answer: Every point on wavefront acts as source of secondary wavelets; envelope of wavelets gives new wavefront. At boundary, wavelets reconstruct reflected wavefront obeying law of reflection.
Q31. What is ionisation energy? How does it vary in hydrogen-like species with Z? (30–50 words.)
Suggested length: up to 45 words · 2 marks
0 / 45 words
How to approach: Write 30–50 words. Open with the law/formula/name, then one-line explanation or numerical step.
NIOS marking: 2 marks = correct law/formula (1) + brief explanation/application (1).
Example: Example: Lenz's law — induced current opposes the change in magnetic flux causing it.
Common mistakes: Long derivation; missing law statement; wrong units; copying notes without answering the question.
Model answer: Energy to remove electron from ground state to infinity. For hydrogen-like atom E_n ∝ −Z² — higher nuclear charge Z binds electron more strongly, ionisation energy increases with Z.
Q32. State Davisson-Germer experiment conclusion. What did it confirm? (30–50 words.)
Suggested length: up to 45 words · 2 marks
0 / 45 words
How to approach: Write 30–50 words. Open with the law/formula/name, then one-line explanation or numerical step.
NIOS marking: 2 marks = correct law/formula (1) + brief explanation/application (1).
Example: Example: Lenz's law — induced current opposes the change in magnetic flux causing it.
Common mistakes: Long derivation; missing law statement; wrong units; copying notes without answering the question.
Model answer: Electrons scattered from nickel crystal showed diffraction pattern like X-rays. Confirmed de Broglie hypothesis — particles exhibit wave nature with λ = h/p.
Q33. State two properties of nuclear force. Why is it called short-range? (30–50 words.)
Suggested length: up to 45 words · 2 marks
0 / 45 words
How to approach: Write 30–50 words. Open with the law/formula/name, then one-line explanation or numerical step.
NIOS marking: 2 marks = correct law/formula (1) + brief explanation/application (1).
Example: Example: Lenz's law — induced current opposes the change in magnetic flux causing it.
Common mistakes: Long derivation; missing law statement; wrong units; copying notes without answering the question.
Model answer: Strong, charge-independent (similar for p-p, n-n, p-n), saturates. Effective only within ~1–3 fm — negligible beyond nuclear size, hence short-range.
Q34. What is controlled chain reaction? Name one control rod material. (30–50 words.)
Suggested length: up to 45 words · 2 marks
0 / 45 words
How to approach: Write 30–50 words. Open with the law/formula/name, then one-line explanation or numerical step.
NIOS marking: 2 marks = correct law/formula (1) + brief explanation/application (1).
Example: Example: Lenz's law — induced current opposes the change in magnetic flux causing it.
Common mistakes: Long derivation; missing law statement; wrong units; copying notes without answering the question.
Model answer: Each fission releases neutrons causing further fission at steady rate — power controlled. Control rods (cadmium or boron) absorb excess neutrons to maintain critical steady state.
Q35. Explain formation of depletion layer at p-n junction at equilibrium. (30–50 words.)
Suggested length: up to 50 words · 2 marks
0 / 50 words
How to approach: Write 30–50 words. Open with the law/formula/name, then one-line explanation or numerical step.
NIOS marking: 2 marks = correct law/formula (1) + brief explanation/application (1).
Example: Example: Lenz's law — induced current opposes the change in magnetic flux causing it.
Common mistakes: Long derivation; missing law statement; wrong units; copying notes without answering the question.
Model answer: Electrons diffuse n→p, holes p→n, leaving immobile ions. Region near junction depleted of mobile carriers — internal field opposes further diffusion until equilibrium.
Q36. Give two advantages of solar cell over thermal power for rural lighting. (30–50 words.)
Suggested length: up to 45 words · 2 marks
0 / 45 words
How to approach: Write 30–50 words. Open with the law/formula/name, then one-line explanation or numerical step.
NIOS marking: 2 marks = correct law/formula (1) + brief explanation/application (1).
Example: Example: Lenz's law — induced current opposes the change in magnetic flux causing it.
Common mistakes: Long derivation; missing law statement; wrong units; copying notes without answering the question.
Model answer: Direct conversion of sunlight — no fuel transport; low pollution and noise; minimal maintenance; suitable for remote areas without grid connection.
Q37. Draw conclusion from rocket propulsion regarding Newton's third law. (30–50 words.)
Suggested length: up to 45 words · 2 marks
0 / 45 words
How to approach: Write 30–50 words. Open with the law/formula/name, then one-line explanation or numerical step.
NIOS marking: 2 marks = correct law/formula (1) + brief explanation/application (1).
Example: Example: Lenz's law — induced current opposes the change in magnetic flux causing it.
Common mistakes: Long derivation; missing law statement; wrong units; copying notes without answering the question.
Model answer: Rocket expels hot gases backward (action); gases exert equal forward reaction on rocket — propulsion in vacuum without pushing against air. Momentum conservation in isolated system.
Q38. A bullet of mass 10 g moving at 300 m·s⁻¹ embeds in 990 g wooden block at rest on smooth surface. Find common velocity. (50–80 words.)
Suggested length: up to 80 words · 3 marks
0 / 80 words
How to approach: Structure: formula/diagram (1) → substitution/working (1) → final answer with units (1). Use 50–80 words.
NIOS marking: 3 marks = formula or labelled diagram (1) + correct working (1) + answer with units (1).
Example: Example: W = mgh = 5×10×2 = 100 J work done against gravity.
Common mistakes: Skipping working; missing units; wrong sign convention; diagram without labels.
Model answer: Conservation momentum: 0.01×300 + 0.99×0 = (0.01+0.99)v → v = 3/1 = 3 m·s⁻¹. Perfectly inelastic — KE not conserved but momentum is.
Q39. Water flows at 2 m·s⁻¹ in pipe of radius 2 cm. Find volume flow rate. (50–80 words.)
Suggested length: up to 70 words · 3 marks
0 / 70 words
How to approach: Structure: formula/diagram (1) → substitution/working (1) → final answer with units (1). Use 50–80 words.
NIOS marking: 3 marks = formula or labelled diagram (1) + correct working (1) + answer with units (1).
Example: Example: W = mgh = 5×10×2 = 100 J work done against gravity.
Common mistakes: Skipping working; missing units; wrong sign convention; diagram without labels.
Model answer: A = πr² = π × (0.02)² = 4π×10⁻⁴ m². Q = Av = 4π×10⁻⁴ × 2 = 8π×10⁻⁴ ≈ 2.51×10⁻³ m³·s⁻¹.
Q40. Explain why Carnot engine efficiency is maximum for given temperature limits. (50–80 words.)
Suggested length: up to 75 words · 3 marks
0 / 75 words
How to approach: Structure: formula/diagram (1) → substitution/working (1) → final answer with units (1). Use 50–80 words.
NIOS marking: 3 marks = formula or labelled diagram (1) + correct working (1) + answer with units (1).
Example: Example: W = mgh = 5×10×2 = 100 J work done against gravity.
Common mistakes: Skipping working; missing units; wrong sign convention; diagram without labels.
Model answer: Carnot cycle is reversible — no irreversible losses (friction, rapid expansion). Any real engine between same T₁, T₂ has lower η because irreversibilities increase entropy; η_Carnot = 1 − T₂/T₁ is upper limit.
Q41. Explain principle of AC generator. Write expression for induced emf. (50–80 words.)
Suggested length: up to 75 words · 3 marks
0 / 75 words
How to approach: Structure: formula/diagram (1) → substitution/working (1) → final answer with units (1). Use 50–80 words.
NIOS marking: 3 marks = formula or labelled diagram (1) + correct working (1) + answer with units (1).
Example: Example: W = mgh = 5×10×2 = 100 J work done against gravity.
Common mistakes: Skipping working; missing units; wrong sign convention; diagram without labels.
Model answer: Coil rotates in magnetic field — flux Φ changes periodically (Faraday's law). ε = −N dΦ/dt = NBAω sin ωt. Slip rings deliver alternating emf to external circuit.
Q42. State Kirchhoff's voltage and current laws. Apply to a single-loop circuit with battery E, resistor R and current I. (80–120 words.)
Suggested length: up to 110 words · 5 marks
0 / 110 words
How to approach: Plan 80–120 words: state law/principle (1) → formula/diagram (1) → derivation or worked example (2) → conclusion (1).
NIOS marking: 5 marks = statement of law (1) + diagram/formula (1) + derivation/working (2) + conclusion with units (1).
Example: Example: State Gauss's law, draw Gaussian surface, derive E = σ/(2ε₀) for infinite sheet, note direction.
Common mistakes: Only definition without working; no diagram where required; arithmetic errors; missing conclusion.
Model answer: Junction rule (KCL): algebraic sum of currents at a node is zero — charge conservation. Loop rule (KVL): algebraic sum of potential differences around closed loop is zero — energy conservation. Single loop: E − IR = 0 → I = E/R. Sign convention: rise in potential (− to + through battery) positive; IR drop opposite to current negative.
Q43. Explain mass-energy equivalence. Define binding energy per nucleon. Why is ⁵⁶Fe near peak of B/A curve? (80–120 words.)
Suggested length: up to 115 words · 5 marks
0 / 115 words
How to approach: Plan 80–120 words: state law/principle (1) → formula/diagram (1) → derivation or worked example (2) → conclusion (1).
NIOS marking: 5 marks = statement of law (1) + diagram/formula (1) + derivation/working (2) + conclusion with units (1).
Example: Example: State Gauss's law, draw Gaussian surface, derive E = σ/(2ε₀) for infinite sheet, note direction.
Common mistakes: Only definition without working; no diagram where required; arithmetic errors; missing conclusion.
Model answer: Einstein E = mc² — mass defect Δm in nucleus converts to binding energy E_b = Δm c² released when nucleus forms. B/A is average binding energy per nucleon — measures stability. Curve rises from light nuclei to peak near ⁵⁶Fe (~8.8 MeV/nucleon) then falls for heavy nuclei. Iron has maximum B/A — neither fission nor fusion of iron releases net energy; lighter fuse, heavier fission toward iron for energy release.