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CBSE Sample Practice Paper — 2 , Session 2026–27)
| Student Name: ______________________ | Roll No.: __________ | Section: __________ |
General Instructions:
1. This question paper is divided into three parts: Part A (Chemistry – 25 marks), Part B (Biology – 30 marks), and Part C (Physics – 25 marks).
2. Each part contains four sections: Section 1 — Very Short Answer (MCQ / Assertion-Reasoning), Section 2 — Short Answer, Section 3 — Long Answer, and Section 4 — Case/Source-based integrated question.
3. Internal choices have been provided in approximately one-third of the questions across the paper; attempt only one option wherever a choice is given.
4. This is a High-Level / HOTS practice edition — questions emphasise application, analysis, prediction and reasoning rather than direct recall.
5. Marks for each question are indicated against it. Support numerical answers with correct formula, working, and units.
6. This is a practice paper prepared in line with the CBSE Class X Science (086) design for the 2026-27 session.
PART A — CHEMISTRY (25 Marks)
Section 1 — Very Short Answer (1 Mark each) — Q1 to Q6
Q1. On adding dilute HCl separately to four metals, which one would NOT produce hydrogen gas? 1
Q2. A colourless gas evolved on adding dilute HCl to zinc granules is passed through a soap solution, and a burning matchstick is brought near the bubbles. What is observed? 1
Q3. Metal A displaces metal B from its salt solution, and metal B displaces metal C from its salt solution. Which metal is the most reactive? 1
Q4. A compound X turns red litmus blue and reacts with zinc metal to liberate hydrogen gas. X is most likely: 1
Q5. An organic compound has the molecular formula C₂H₄O₂ and turns blue litmus red. It is most likely: 1
Q6. Assertion (A): Ionic compounds generally have high melting and boiling points.
Reason (R): Ionic compounds have strong electrostatic forces of attraction between oppositely charged ions, requiring a large amount of energy to overcome. 1
Reason (R): Ionic compounds have strong electrostatic forces of attraction between oppositely charged ions, requiring a large amount of energy to overcome. 1
Section 2 — Short Answer (2 Marks each) — Q7 to Q9
Q7. A student added dilute sulphuric acid to zinc granules in a test tube and collected the gas evolved. On bringing a burning matchstick near the mouth of the test tube, the gas burned with a pop sound. Identify the gas and write the balanced chemical equation for the reaction. 2
Q8. On heating blue-coloured copper(II) nitrate crystals strongly in a boiling tube, a black residue is formed along with a brown gas. Identify the type of reaction taking place and write the balanced chemical equation. 2
Q9. Equal-sized pieces of two metals X and Y are separately dropped into excess dilute HCl. Metal X reacts vigorously with rapid gas evolution, while metal Y reacts very slowly. Arrange X and Y in order of decreasing reactivity, and justify your answer. 2
— OR —
A copper sulphate solution was stored overnight in an iron vessel. The next morning, a hole was found in the vessel. Explain the reason for this observation with a chemical equation. 2
Section 3 — Long Answer (3 & 5 Marks) — Q10 to Q11
Q10. Three unlabelled colourless test tubes contain dilute HCl, dilute NaOH, and a neutral solution respectively. Using only red and blue litmus paper, design a short experiment (steps and expected observations) to correctly identify the contents of each test tube. 3
— OR —
A milkman adds a small amount of baking soda to fresh milk before storing it. (a) Explain why this shifts the pH of milk from about 6 to slightly alkaline. (b) Why does this treated milk take longer than usual to set into curd? 3
Q11. (a) Compound A (an alcohol) reacts with ethanoic acid in the presence of concentrated H₂SO₄ to give a sweet-smelling compound B. Name the class of this reaction, identify B if A is ethanol, and write the chemical equation. (3)
(b) Carbon compounds generally form covalent bonds rather than ionic bonds. Explain why, based on the electronic configuration of carbon. (2) 5
(b) Carbon compounds generally form covalent bonds rather than ionic bonds. Explain why, based on the electronic configuration of carbon. (2) 5
— OR —
(a) A hydrocarbon with formula C₅H₁₂ does not decolourise bromine water, while a hydrocarbon C₅H₁₀ does. Identify the class to which each hydrocarbon belongs, and justify your answer based on the nature of bonding present. (3)
(b) Diamond is extremely hard, while graphite is soft and slippery, even though both are made up entirely of carbon atoms. Explain this difference on the basis of their structures. (2) 5
(b) Diamond is extremely hard, while graphite is soft and slippery, even though both are made up entirely of carbon atoms. Explain this difference on the basis of their structures. (2) 5
Section 4 — Case-Based Question — Q12
Read the following passage and answer the questions that follow:
In an experiment, four metals P, Q, R and S were each dipped into freshly prepared salt solutions of the other three metals, and the results were recorded. It was observed that: P displaces Q, R and S from their respective salt solutions; Q displaces R and S but does not displace P; R displaces S but does not displace P or Q; S does not displace any of the other three metals from their salt solutions.
In an experiment, four metals P, Q, R and S were each dipped into freshly prepared salt solutions of the other three metals, and the results were recorded. It was observed that: P displaces Q, R and S from their respective salt solutions; Q displaces R and S but does not displace P; R displaces S but does not displace P or Q; S does not displace any of the other three metals from their salt solutions.
Q12. (i) Arrange the metals P, Q, R and S in decreasing order of reactivity. (1)
(ii) Which of the four metals is the least reactive? (1)
(iii) If metal R is dipped into a solution of P's salt, will a displacement reaction occur? Justify your answer. (2)
(iv) Name one metal from the actual reactivity series that behaves similarly to S, i.e., is unreactive and often found in the free state in nature. (1) 5
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PART B — BIOLOGY (30 Marks)
Section 1 — Very Short Answer (1 Mark each) — Q13 to Q21
Q13. A cross between a tall pea plant (Tt) and a short pea plant (tt) is most likely to produce offspring in which ratio? 1
Q14. Which statement best explains why variation among individuals is important for the survival of a species? 1
Q15. A patient's blood glucose level remains abnormally high even after eating. Malfunction of which gland is most likely responsible? 1
Q16. During a sudden "fight or flight" response, which of the following changes would you expect in the body? 1
Q17. Two plants of the same species, grown in identical soil and climate conditions, show different heights. This variation is most likely due to: 1
Q18. A potted plant kept near a window is observed to bend its stem towards the source of light. This response is an example of: 1
Q19. Which statement correctly explains why a food chain usually does not have more than 3–4 trophic levels? 1
Q20. Which of the following correctly represents the pathway of a nerve impulse during a reflex action? 1
Q21. Assertion (A): Plants produced through vegetative propagation are genetically identical to the parent plant.
Reason (R): Vegetative propagation is a form of asexual reproduction that involves only mitotic cell division, without fusion of gametes. 1
Reason (R): Vegetative propagation is a form of asexual reproduction that involves only mitotic cell division, without fusion of gametes. 1
Section 2 — Short Answer (2 Marks each) — Q22 to Q25
Q22. A person's pupil is observed to constrict rapidly when a bright light is suddenly shone into the eye. Identify the type of action this represents and briefly explain the response. 2
Q23. Explain, with reasoning, why the response of a plant to a stimulus (such as touch or light) is generally much slower than the response of an animal to a similar stimulus. 2
— OR —
A gardener notices that touching the leaves of a "touch-me-not" (Mimosa) plant causes them to fold rapidly, without any growth taking place. Explain how this response occurs without involving cell growth. 2
Q24. Two tall pea plants (Tt × Tt) are crossed, and the offspring produced include both tall and short plants. Explain why this happens, using the concept of dominant and recessive alleles. 2
Q25. A pond that receives excess fertiliser runoff from nearby farms shows rapid, excessive growth of algae, followed later by large-scale death of fish. Explain the likely sequence of events leading to the death of the fish. 2
Section 3 — Long Answer (3 & 5 Marks) — Q26 to Q27
Q26. A person meets with an accident that damages the medulla region of the brain. Based on the known functions of the medulla, predict and explain three possible effects this could have on the person's body functioning. 3
— OR —
Using suitable examples, explain how voluntary actions and involuntary (reflex) actions differ in terms of the neural pathway involved and the speed of response. 3
Q27. (a) A cross between a tall, round-seeded pea plant and a short, wrinkled-seeded pea plant produces an F1 generation that is entirely tall and round-seeded. Explain what this indicates about dominance, and predict the genotypic and phenotypic ratio expected in the F2 generation for a monohybrid cross considering only the seed-shape trait. (3)
(b) Why are the traits that appear in the F1 generation referred to as 'dominant' traits? (2) 5
(b) Why are the traits that appear in the F1 generation referred to as 'dominant' traits? (2) 5
— OR —
(a) Explain, with reasons, how the processes of nutrition, respiration and excretion in a unicellular organism such as Amoeba are fundamentally different from the same processes in a large multicellular organism such as a human, even though the basic life processes are the same. (3)
(b) Why do multicellular organisms require specialised organ systems to carry out these processes, while unicellular organisms do not? (2) 5
(b) Why do multicellular organisms require specialised organ systems to carry out these processes, while unicellular organisms do not? (2) 5
Section 4 — Case-Based Question — Q28
Read the following passage and answer the questions that follow:
A 45-year-old man visits a doctor with complaints of frequent urination, excessive thirst, and persistent fatigue. Blood tests reveal that his blood glucose level remains significantly higher than normal even after an overnight fast. The doctor diagnoses a hormonal disorder related to blood sugar regulation and recommends both lifestyle changes and medication to manage the condition.
A 45-year-old man visits a doctor with complaints of frequent urination, excessive thirst, and persistent fatigue. Blood tests reveal that his blood glucose level remains significantly higher than normal even after an overnight fast. The doctor diagnoses a hormonal disorder related to blood sugar regulation and recommends both lifestyle changes and medication to manage the condition.
Q28. (i) Name the hormone whose deficiency or reduced action is most likely responsible for this condition. (1)
(ii) Name the gland that secretes this hormone. (1)
(iii) Explain how this hormone normally regulates blood glucose level in a healthy person. (2)
(iv) Suggest one lifestyle change that could help this patient manage his condition. (1) 5
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PART C — PHYSICS (25 Marks)
Section 1 — Very Short Answer (1 Mark each) — Q29 to Q34
Q29. A student obtains a sharp, well-defined image of a distant tree on a screen using a concave mirror. Which measurement should be taken to approximately determine the focal length of the mirror? 1
Q30. Two resistors, each of resistance R, are first connected in series and then in parallel. The ratio of their equivalent resistance in series to that in parallel is: 1
Q31. A convex lens forms a real, diminished image of an object. Where must the object have been placed? 1
Q32. If the current through a resistor is doubled while its resistance is kept constant, the heat produced in a given time becomes: 1
Q33. A person is prescribed a concave lens to correct a defect of vision. This indicates that the defect is: 1
Q34. Assertion (A): In a household electric circuit, appliances are connected in parallel rather than in series.
Reason (R): A parallel connection ensures that each appliance receives the same voltage and can operate independently, so that one appliance failing does not stop the others from working. 1
Reason (R): A parallel connection ensures that each appliance receives the same voltage and can operate independently, so that one appliance failing does not stop the others from working. 1
Section 2 — Short Answer (2 Marks each) — Q35 to Q37
Q35. A wire of resistance R is cut into two equal halves, and both halves are then connected in parallel with each other. Calculate the new equivalent resistance in terms of R, showing your working clearly. 2
Q36. An object is placed at a distance of 30 cm from a concave mirror whose focal length is 15 cm. Without using the mirror formula, predict the position and nature of the image formed, using the property of a concave mirror when an object is placed at its centre of curvature. 2
— OR —
A convex lens produces a virtual image that is twice the size of the object. State, with reasoning, where the object must be positioned relative to the focus of the lens for this to occur. 2
Q37. A student notices that a bulb glows brighter when connected alone in a circuit with a battery, but becomes noticeably dimmer when a second identical resistor is added in series with it. Explain this observation using the concept of resistance and current. 2
Section 3 — Long Answer (3 & 5 Marks) — Q38 to Q39
Q38. A ray of light travelling from air into water is observed to bend towards the normal. Using the concept of refractive index and the speed of light in different media, explain why this bending occurs. Also state what would happen to the ray if it travelled from water into air instead. 3
— OR —
A student traces the path of a ray of light passing through a triangular glass prism and compares it with the path of a ray passing through a rectangular glass slab. Predict and explain why the emergent ray in the two cases is not parallel to the incident ray in the same way. 3
Q39. (a) In a circuit, three resistors of 2 Ω, 3 Ω and 5 Ω are connected first in series, and then in parallel, to a 10 V battery. Calculate the total current drawn from the battery in each case. (3)
(b) Which combination — series or parallel — would you prefer for connecting bulbs and appliances in a home, and why? (2) 5
(b) Which combination — series or parallel — would you prefer for connecting bulbs and appliances in a home, and why? (2) 5
— OR —
(a) A straight current-carrying conductor is placed perpendicular to a magnetic field. Using Fleming's left-hand rule, explain how the direction of the force experienced by the conductor can be determined if the directions of current and field are known. (3)
(b) Explain why a current-carrying conductor placed parallel to a magnetic field experiences no force. (2) 5
(b) Explain why a current-carrying conductor placed parallel to a magnetic field experiences no force. (2) 5
Section 4 — Case-Based Question — Q40
Read the following passage and answer the questions that follow:
A family's home circuit has a refrigerator, an air conditioner, an electric heater and several lights, all connected in parallel to the mains supply, protected by a fuse rated at 5 A. One evening, the family switches on the heater and the air conditioner simultaneously, along with the refrigerator and lights already running, and the fuse suddenly blows, cutting off power to the entire house.
A family's home circuit has a refrigerator, an air conditioner, an electric heater and several lights, all connected in parallel to the mains supply, protected by a fuse rated at 5 A. One evening, the family switches on the heater and the air conditioner simultaneously, along with the refrigerator and lights already running, and the fuse suddenly blows, cutting off power to the entire house.
Q40. (i) Why did the fuse blow in this situation? (1)
(ii) What does this event indicate about the total current being drawn from the circuit at that time, compared to the fuse's rated value? (1)
(iii) Explain how the fuse protects the household wiring and appliances from being damaged in such a situation. (2)
(iv) Suggest one precaution the family should take in future to avoid this situation. (1) 5
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Design of Question Paper — Blueprint & Analysis
1. Part-wise Marks Distribution
| Part | Subject / Unit | Total Marks |
|---|---|---|
| A | Chemistry — Unit I: Chemical Substances (Nature and Behaviour) | 25 |
| B | Biology — Unit II: World of Living (25) + Unit V: Natural Resources (5) | 30 |
| C | Physics — Unit III: Natural Phenomena (12) + Unit IV: Effects of Current (13) | 25 |
| Total | 80 | |
2. Section-wise Typology (per Part)
| Section | Question Type | Chemistry | Biology | Physics |
|---|---|---|---|---|
| 1 | VSA (MCQ incl. 1 Assertion–Reason) | 6 × 1 = 6 | 9 × 1 = 9 | 6 × 1 = 6 |
| 2 | Short Answer (2 marks) | 3 × 2 = 6 | 4 × 2 = 8 | 3 × 2 = 6 |
| 3 | Long Answer (3 + 5 marks) | 3 + 5 = 8 | 3 + 5 = 8 | 3 + 5 = 8 |
| 4 | Case-Based (5 marks) | 5 | 5 | 5 |
| Part Total | 25 | 30 | 25 | |
3. Competency-Level Distribution — High-Level / HOTS Edition
| Competency Level | Description | Approx. Marks | Percentage |
|---|---|---|---|
| Knowledge & Understanding | State, define, list, describe, identify | 28 | 35% |
| Application of Knowledge | Calculate, illustrate, show, explain, distinguish | 26 | 32.5% |
| Analyse, Evaluate & Create (HOTS) | Interpret, analyse, compare, contrast, examine, predict, justify | 26 | 32.5% |
| Total | 80 | 100% |
Note: This edition raises the share of application and HOTS-based questions relative to a standard-difficulty paper (typically 50:30:20), to give stronger practice for analytical, prediction-based and reasoning-heavy board-level questions.
4. Internal Choice Summary
Internal choices are provided in Q9, Q11, Q23, Q27, Q36, Q39 and one sub-part group each in the case-based questions where applicable — approximately one-third of the total questions across the paper.
5. Topics Excluded (as per current 2026-27 exclusions)
• Periodic Classification of Elements (Unit I)
• Evolution — speciation, fossils, evidence of evolution (only Heredity/Mendelian genetics is retained from this chapter)
• Electric Motor, Electromagnetic Induction, and Electric Generator (Unit IV)
• Content found only in "Do You Know?" / additional-information boxes of the NCERT textbook
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Answer Key
Part A — Chemistry
Q1. (C) Copper Q2. (B) Bubbles burst with a pop sound Q3. (A) A Q4. (B) NaOH Q5. (B) Ethanoic acid Q6. (A)
Q7. Gas is hydrogen (H₂); Zn + H₂SO₄ → ZnSO₄ + H₂↑.
Q8. Thermal decomposition reaction: 2Cu(NO₃)₂ → 2CuO + 4NO₂↑ + O₂↑ (black residue is CuO, brown gas is NO₂).
Q9. X is more reactive than Y, because a more reactive metal displaces hydrogen from dilute acid more vigorously and rapidly than a less reactive one. OR: Iron is more reactive than copper, so it displaces copper from copper sulphate solution: Fe + CuSO₄ → FeSO₄ + Cu; the reaction gradually corrodes/dissolves the iron vessel, forming a hole.
Q10. Dip red and blue litmus into each solution: the one that turns blue litmus red is dilute HCl; the one that turns red litmus blue is dilute NaOH; the one that causes no colour change in either is the neutral solution. OR: (a) Milk is naturally slightly acidic (pH ~6); adding baking soda (a base) shifts it towards alkaline to slow down the souring process. (b) Since curdling is caused by lactic acid bacteria, and the milk is now less acidic to begin with, it takes longer for the bacteria to lower the pH enough to curdle the milk.
Q11. (a) Esterification reaction; compound B is ethyl ethanoate (a sweet-smelling ester): CH₃COOH + C₂H₅OH → CH₃COOC₂H₅ + H₂O (in presence of conc. H₂SO₄). (b) Carbon has 4 valence electrons; it would need to gain or lose 4 electrons to attain a stable octet, which requires too much energy, so it shares electrons (covalent bonding) instead of forming ions. OR: (a) C₅H₁₂ is a saturated hydrocarbon (alkane) with only single bonds, so it does not react with/decolourise bromine water; C₅H₁₀ is an unsaturated hydrocarbon (alkene) containing a double bond, which reacts with bromine water, decolourising it. (b) In diamond, each carbon atom is bonded to four others in a rigid 3D tetrahedral network, making it very hard; in graphite, carbon atoms form layers of hexagonal rings with weak forces between layers, allowing layers to slide over each other, making it soft and slippery.
Q12. (i) P > Q > R > S. (ii) S. (iii) No reaction will occur, because R is less reactive than P, and a less reactive metal cannot displace a more reactive metal from its salt solution. (iv) Gold (or silver/platinum) — unreactive metals found free in nature.
Part B — Biology
Q13. (C) 1:1 tall:short Q14. (B) Q15. (B) Pancreas Q16. (B) Q17. (B) Genetic differences Q18. (B) Phototropism Q19. (B) Q20. (B) Q21. (A)
Q22. This is a reflex action, controlled involuntarily by the nervous system; bright light causes the circular muscles of the iris to contract, reducing pupil size to limit the amount of light entering the eye and protect the retina.
Q23. Plants lack a nervous system and specialised muscle tissue for rapid movement; their responses generally occur through slower processes like differential growth caused by hormones (e.g., auxin), which take more time compared to the fast electrical nerve impulses used by animals. OR: The rapid folding of Mimosa leaves occurs due to a sudden change in water pressure (turgor) in specialised cells at the base of the leaflets, not due to growth, allowing an immediate response to touch.
Q24. Since T (tall) is dominant and t (short) is recessive, the Tt × Tt cross produces a genotypic ratio of 1 TT : 2 Tt : 1 tt, giving a phenotypic ratio of 3 tall : 1 short — the recessive trait (short) reappears in plants that inherit two copies of the recessive allele (tt).
Q25. Excess nutrients cause algae to grow and multiply rapidly (algal bloom); when the algae die, decomposer bacteria multiply and consume large amounts of dissolved oxygen in the water while breaking them down, drastically reducing oxygen levels and causing fish to suffocate and die.
Q26. Possible effects: (1) disruption of breathing/respiratory rate control, since the medulla regulates involuntary functions like breathing; (2) irregular heartbeat, as the medulla also helps control heart rate; (3) impaired reflexes such as swallowing, coughing, or vomiting reflexes, which are coordinated by the medulla. OR: Voluntary actions are consciously controlled by the cerebrum (forebrain) and involve a longer neural pathway through the brain, making them relatively slower; reflex actions bypass the brain, being controlled directly by the spinal cord through a short reflex arc, making them much faster (e.g., withdrawing a hand from a hot object).
Q27. (a) Since F1 is entirely tall and round, tallness and round shape are dominant traits over shortness and wrinkled shape; for a monohybrid cross of Rr × Rr (round vs wrinkled), the F2 genotypic ratio is 1 RR : 2 Rr : 1 rr, and the phenotypic ratio is 3 round : 1 wrinkled. (b) They are called dominant because they are the traits that are expressed/visible in the F1 generation, masking the recessive trait, which is present but not visibly expressed. OR: (a) Amoeba, being unicellular, carries out all life processes (nutrition, respiration, excretion) through its single cell surface and cytoplasm by simple diffusion; in humans, these processes require specialised organs and organ systems (digestive, respiratory, excretory systems) because cells are far from the body surface and diffusion alone is not sufficient. (b) As organisms become larger and multicellular, the surface area-to-volume ratio decreases, so simple diffusion cannot meet the needs of all cells; specialised organ systems are needed to transport substances efficiently to and from every cell.
Q28. (i) Insulin. (ii) Pancreas. (iii) Insulin lowers blood glucose level by promoting the uptake of glucose by body cells and its conversion to glycogen for storage in the liver and muscles, keeping blood sugar within a normal range. (iv) Regular physical exercise / a balanced, low-sugar diet (any one reasonable suggestion).
Part C — Physics
Q29. (A) Distance between the mirror and the screen Q30. (C) 4:1 Q31. (C) Beyond 2F Q32. (C) Four times Q33. (B) Myopia Q34. (A)
Q35. Each half has resistance R/2. In parallel: 1/Req = 1/(R/2) + 1/(R/2) = 2/R + 2/R = 4/R ⇒ Req = R/4.
Q36. At a distance of 30 cm (which equals 2F, since f = 15 cm ⇒ 2F = 30 cm), the object is at the centre of curvature; the image formed is real, inverted, of the same size as the object, and also located at the centre of curvature (30 cm). OR: For a convex lens to form a virtual, magnified image twice the size of the object, the object must be placed between the lens and its focus (i.e., at a distance less than f), since only then does a convex lens act like a magnifying glass and produce a virtual, erect, enlarged image.
Q37. Adding a second resistor in series increases the total resistance of the circuit; since current I = V/R, an increase in total resistance (with V unchanged) decreases the current flowing through the circuit, so the bulb receives less current and glows dimmer.
Q38. Light travels slower in water (denser medium) than in air; this reduction in speed as light enters a denser medium causes it to bend towards the normal (this bending is quantified by the refractive index of water relative to air). If light travels from water into air instead, it would bend away from the normal, since it is now moving into a less dense (rarer) medium where its speed increases. OR: In a prism, due to its non-parallel refracting surfaces, the ray bends at both surfaces in the same direction, causing an overall deviation and the emergent ray is not parallel to the incident ray; in a rectangular slab, the two refracting surfaces are parallel, so the bending at the first surface is exactly reversed at the second, and the emergent ray is parallel to the incident ray (though laterally displaced).
Q39. (a) Series: Rs = 2+3+5 = 10 Ω; I = V/R = 10/10 = 1 A. Parallel: 1/Rp = 1/2 + 1/3 + 1/5 = 15/30+10/30+6/30 = 31/30 ⇒ Rp = 30/31 Ω ≈ 0.97 Ω; I = 10/(30/31) = 31/3 ≈ 10.33 A. (b) Parallel combination is preferred for home wiring, because each appliance gets full voltage and works independently; if one appliance fails or is switched off, others continue to function normally, unlike in series. OR: (a) Point the thumb of the left hand in the direction of current flow and the first finger in the direction of the magnetic field; the second finger (held perpendicular to both) then points in the direction of the force experienced by the conductor. (b) When the conductor is parallel to the magnetic field, the angle between current direction and field direction is 0°, and since force F = BIL sinθ, force becomes zero when θ = 0°.
Q40. (i) The combined current drawn by all appliances running simultaneously (heater, AC, fridge, lights) exceeded the fuse's rated current of 5 A. (ii) It indicates that the total current flowing through the circuit at that time was greater than 5 A, i.e., the circuit was overloaded. (iii) The fuse wire, made of a low-melting-point alloy, heats up and melts once current exceeds the rated safe value, breaking the circuit and cutting off the power supply before the excess current can damage the wiring or connected appliances. (iv) Avoid running high-power appliances like the heater and air conditioner simultaneously with other heavy loads; use separate circuits/higher-rated fuses for high-power appliances as recommended by an electrician.
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Detailed Marking Scheme
General Marking Guidelines
• Section 1 (MCQ/Assertion-Reason): 1 mark for the correct option only; no partial credit.
• Section 2 (2-mark questions): 1 mark for the correct concept/reasoning, 1 mark for correct explanation, justification, or calculation as applicable.
• Section 3 (3 & 5-mark questions): marks awarded step-wise — correct concept/law/prediction, correct reasoning/working, and a well-justified conclusion. Since this is a HOTS edition, credit should be given generously for logically sound reasoning even if phrased differently from the model answer.
• Section 4 (Case-based, 5 marks): each sub-part carries independent marks as indicated (1, 1, 2, 1); an error in one sub-part should not affect marks for the others.
• Numerical questions: full credit only if correct formula, correct substitution, correct final answer with unit are all present; partial credit for correct formula/substitution even if the final numeric answer has a minor computational error.
• Predictive/justification-type HOTS questions: credit the underlying scientific reasoning and logical consistency of the answer, not just the final stated conclusion.
Part-wise Mark Allocation Recap
| Part | Section 1 | Section 2 | Section 3 | Section 4 | Total |
|---|---|---|---|---|---|
| A — Chemistry | 6 | 6 | 8 | 5 | 25 |
| B — Biology | 9 | 8 | 8 | 5 | 30 |
| C — Physics | 6 | 6 | 8 | 5 | 25 |
| Grand Total | 21 | 20 | 24 | 15 | 80 |
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