CBSE Class X Science • Sample Paper Set 7 with Complete Solutions • Academic Session 2026–2027

CBSE Class 10 Science Sample Paper Set 7 | 2026-2027 | Adept Yourself

General Instructions:

This question paper consists of 39 questions divided into Sections A, B and C.
All questions are compulsory.
Internal choices are provided in some questions. Attempt only one alternative wherever applicable.
Questions include MCQs, Assertion–Reason, Very Short Answer, Short Answer, Case-Based and Long Answer questions.
Marks are indicated against each question.
Write all answers clearly and show necessary calculations wherever required.
Draw neat and properly labelled diagrams wherever asked.

SECTION A – BIOLOGY

Q1. Which enzyme present in saliva breaks down complex starch molecules into simple sugars?[1]

(a) Pepsin

(b) Salivary amylase

(d) Lipase

Q2. The unidirectional growth of a plant root towards moisture is an example of:[1]

(a) Phototropism

(b) Geotropism

(d) Chemotropism

Q3. Spore formation is the common method of asexual reproduction observed in:[1]

(a) Rhizopus (Bread mould)

(b) Spirogyra

(d) Amoeba

Q4. Which blood vessel brings oxygen-rich blood from the lungs into the left atrium of the human heart?[1]

(a) Vena cava

(b) Pulmonary artery

(d) Aorta

Q5. A cross between a homozygous round yellow pea plant (RRYY) and a wrinkled green pea plant (rryy) produces F₁ progeny that are all:[1]

(a) Round green

(b) Wrinkled yellow

(d) Wrinkled green

Q6. In an ecosystem, which of the following groups constitutes a functional food chain?[1]

(a) Grass, Wheat and Mango

(b) Grass, Goat and Human

(d) Grass, Fish and Goat

Q7.Assertion (A): Iodised salt is recommended in our daily diet to prevent goitre.
Reason (R): Iodine is essential for the thyroid gland to synthesise the hormone thyroxin.[1]

(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.

Q8.Assertion (A): Valves are present in veins but absent in arteries.
Reason (R): Blood flows through veins at low pressure, and valves prevent its backflow.[1]

Q9. What is the function of the cartilaginous rings present in the human trachea (windpipe)?[2]

Q10. Name any two barrier methods of contraception and explain how they prevent pregnancy.[2]

Q11.(a) Define chemotropism. Give one biological example of chemotropism in plants.
(b) Which plant hormone is responsible for the wilting and falling of yellowed leaves?
(c) How does the touch-me-not plant (Mimosa pudica) show rapid movement in response to touch?[3]

Q12. Explain how the sex of a newly formed zygote is genetically determined in human beings. Use a genetic cross chart to illustrate your answer.[3]

Q13. Differentiate between arteries and veins based on:
(a) Wall thickness (b) Direction of blood flow (c) Presence of valves[3]

Q14. Read the following passage and answer the questions:[4]

During digestion, complex macromolecules are broken down into absorbable units. Proteins are digested into amino acids, carbohydrates into glucose, and fats into fatty acids and glycerol. The small intestine is the site of complete digestion. The digested food is absorbed through villi, while unabsorbed material enters the large intestine where water is absorbed before egestion.

(a) Name the protein-digesting enzyme present in gastric juice and state the condition required for its activation.
(b) What is the main function of the large intestine in human beings?
(c) Explain the dual role played by pancreatic juice in digestion.
OR
How does the liver assist in the digestion of fats despite producing no digestive enzymes?

Q15.(a) Draw a neat labelled diagram of a human nephron showing its major parts.
(b) Describe the three main stages involved in urine formation:
    (i) Glomerular filtration
    (ii) Tubular reabsorption
    (iii) Tubular secretion
(c) What is the function of the urinary bladder?[5]

(a) Explain the process of budding in Hydra with sequential diagrams.
(b) Differentiate between regeneration and reproduction. Why is regeneration not considered a true method of reproduction in complex organisms?
(c) Mention two advantages of vegetative propagation in agriculture.

SECTION B – CHEMISTRY

Q16. Which of the following indicators turns reddish-pink in a basic solution?[1]

(a) Blue litmus

(b) Methyl orange

(d) Red litmus

Q17. The chemical formula of washing soda is:[1]

(a) Na₂CO₃ · H₂O

(b) Na₂CO₃ · 10H₂O

(d) CaSO₄ · 2H₂O

Q18. Which of the following non-metals is a liquid at room temperature?[1]

(a) Iodine

(b) Carbon

(d) Sulphur

Q19. The structural formula of ethanoic acid contains:[1]

(a) An aldehyde group (–CHO)

(b) A ketone group (–CO–)

(d) An alcohol group (–OH)

Q20. When barium chloride solution reacts with sodium sulphate solution, a white precipitate is formed. The chemical reaction is an example of a:[1]

(a) Displacement reaction

(b) Double displacement reaction

(d) Combination reaction

Q21.Assertion (A): Pure gold (24 carat) is not suitable for making jewellery.
Reason (R): Pure gold is very soft, so it is alloyed with copper or silver to make it hard and durable.[1]

Q22. Why do chips manufacturers flush bags of chips with nitrogen gas? Name the phenomenon prevented by this process.[2]

Q23. Write balanced chemical equations for the following reactions:
(a) Aluminium powder is heated with manganese dioxide.
(b) Iron reacts with steam.
(c) Calcium reacts with water.[3]

(a) Define an alloy. Give the composition and one use of Brass and Solder.
(b) What is an amalgam?

Q24.(a) Why does carbon form compounds mainly by covalent bonding rather than by forming $C^{4+}$ or $C^{4-}$ ions?
(b) Draw the electron dot structure of an ethyne molecule ($C_2H_2$).[3]

Q25. Read the following passage and answer the questions:[4]

Universal indicator is a mixture of several dyes that shows different colours at different concentrations of hydrogen ions in a solution. The pH scale measures hydrogen ion concentration from 0 (very acidic) to 14 (very alkaline). Solutions with pH less than 7 are acidic, pH 7 is neutral, and pH greater than 7 is basic. Living organisms function within narrow pH limits.

(a) Solution A has a pH of 3 and Solution B has a pH of 9. Which solution has a higher concentration of $H^+$ ions?
(b) What is the colour change observed when universal indicator paper is dipped into pure distilled water?
(c) Explain why the soil of an agricultural field is treated with quicklime ($CaO$) or slaked lime ($Ca(OH)_2$).
OR
Explain how antacids provide relief from acidity in the stomach. Name two chemical compounds commonly used as antacids.

Q26.(a) Explain the mechanism of micelle formation during the cleansing action of soap.
(b) Draw a neat diagram of a soap micelle showing its hydrophilic and hydrophobic ends.
(c) Why do synthetic detergents form lather easily even in hard water, whereas soaps form scum?[5]

(a) Give the chemical name and formula of Bleaching Powder.
(b) Write the balanced chemical equation for the preparation of bleaching powder.
(c) State three commercial uses of bleaching powder.
(d) What happens when bleaching powder is left exposed to open air for a long time? Write the reaction.

Q27. State two differences between a physical change and a chemical change with one example of each.[2]

SECTION C – PHYSICS

Q28. A ray of light striking a plane mirror at an angle of incidence of 35° is reflected. The angle of deviation of the ray is:[1]

(a) 35°

(b) 70°

(d) 145°

Q29. The resistance of a metallic wire of length $L$ and uniform cross-sectional area $A$ is $16\ \Omega$. If the wire is cut into four equal parts, the resistance of each part will be:[1]

(a) 4 Ω

(b) 8 Ω

(d) 1 Ω

Q30. The phenomenon responsible for the early sunrise and delayed sunset is:[1]

(a) Total internal reflection

(b) Atmospheric refraction

(d) Tyndall scattering

Q31. The strength of the magnetic field inside a current-carrying long straight solenoid:[1]

(a) Decreases as we move towards its ends

(b) Increases as we move towards its ends

(d) Is uniform at all points inside

Q32.Assertion (A): Danger signals and stoplights installed at traffic intersections are always red in colour.
Reason (R): Red light has the longest wavelength among visible colours and is scattered the least by fog and smoke particles.[1]

Q33.Assertion (A): The equivalent resistance of a group of resistors connected in parallel is always less than the smallest individual resistance in the group.
Reason (R): In a parallel combination, the total cross-sectional area for current flow effectively increases, offering alternate pathways for current.[1]

Q34. An object is placed at a distance of 12 cm in front of a concave mirror of focal length 20 cm. Find the position of the image and state whether it is real or virtual.[2]

Q35. Define 1 volt of electric potential difference. Write its SI formula.[2]

A current of 0.5 A is drawn by a filament of an electric bulb for 10 minutes. Calculate the total electric charge that flows through the circuit.

Q36.(a) What is the Tyndall effect?
(b) Give two daily-life examples where the Tyndall effect is observed.
(c) Why do fine colloidal particles scatter blue light more strongly than red light?[3]

Q37. State the principle of an electric generator (or dynamo) and differentiate between alternating current (AC) and direct current (DC).[3]

Q38. Read the following passage and answer the questions:[4]

Electric power is the rate at which electrical energy is consumed in an electrical circuit ($P = V I = I^2 R = \frac{V^2}{R}$). In household circuits, appliances are rated by their operating voltage and power consumption (e.g., 220 V, 100 W). The commercial unit of electrical energy is the kilowatt-hour (kWh), commonly called a “unit” of electricity. $1\text{ kWh} = 3.6 \times 10^6\text{ J}$.

(a) Define electric power and state its SI unit.
(b) An electric bulb is rated 220 V, 100 W. Calculate its operating resistance.
(c) If this bulb runs for 5 hours daily for a month of 30 days, calculate the electrical energy consumed in kWh.
OR
Two lamps, one rated 100 W at 220 V, and the other 60 W at 220 V, are connected in parallel to a 220 V supply. Calculate the total current drawn from the line.

Q39.(a) A convex mirror used for rear-view on an automobile has a radius of curvature of 3.00 m. If a bus is located at 5.00 m from this mirror, find the position, nature, and magnification of the image.
(b) Define the power of a lens. A doctor prescribes a corrective lens of power +1.5 D. Find the focal length of the lens. Is the prescribed lens diverging or converging?[5]

(a) Draw the magnetic field lines around a bar magnet. State three important properties of magnetic field lines.
(b) Describe an experiment to demonstrate that a current-carrying conductor experiences a mechanical force when placed inside a magnetic field.

CBSE CLASS X SCIENCE – COMPLETE SOLUTIONS & MARKING SCHEME (SET – 7)

SECTION A – BIOLOGY SOLUTIONS

Q1. (b) Salivary amylase [1 Mark]
Explanation: Saliva contains the enzyme salivary amylase (ptyalin) that breaks down starch into maltose and simple sugars at an optimum pH of around 6.8.

Q2. (c) Hydrotropism [1 Mark]
Explanation: The directional growth response of plant roots towards moisture/water is called positive hydrotropism.

Q3. (a) Rhizopus (Bread mould) [1 Mark]
Explanation: Rhizopus produces hundreds of microscopic reproductive structures called spores inside swollen sporangiophores. When the sporangia burst, the airborne spores germinate upon finding moist surfaces.

Q4. (c) Pulmonary vein [1 Mark]
Explanation: Pulmonary veins carry freshly oxygenated blood from the lungs into the left atrium of the heart.

Q5. (c) Round yellow [1 Mark]
Explanation: In Mendel’s dihybrid cross, the F₁ generation inherits dominant alleles for both traits (genotype RrYy), expressing the dominant phenotype: round yellow seeds.

Q6. (b) Grass, Goat and Human [1 Mark]
Explanation: Grass (producer) is consumed by Goat (herbivore/primary consumer), which in turn can be consumed by Human (omnivore/secondary consumer), forming a valid food chain.

Q7. (a) Both A and R are true and R is the correct explanation of A. [1 Mark]
Explanation: Iodine is a key structural component required by the thyroid gland to synthesise thyroxin. A deficiency of iodine impairs thyroxin production, causing thyroid swelling known as goitre.

Q8. (a) Both A and R are true and R is the correct explanation of A. [1 Mark]
Explanation: Blood in veins is under low pressure after passing through capillaries. Internal semilunar valves ensure blood flows only towards the heart and cannot flow backward under gravity.

Q9. Cartilaginous Rings in Trachea: [2 Marks]

The trachea is lined with C-shaped rings of hyaline cartilage. [1 Mark]
These rings provide mechanical structural support, preventing the airway from collapsing when there is less air pressure inside the trachea during exhalation. [1 Mark]

Q10. Barrier Methods of Contraception: [2 Marks]

Examples: Condoms (male/female) and Diaphragms/Cervical caps. [1 Mark]
Mechanism: They act as physical barriers that prevent the entry of sperms into the female reproductive tract (uterus/fallopian tubes), thereby preventing fertilization of the ovum. [1 Mark]

Q11. Plant Responses and Hormones: [3 Marks]

(a) Chemotropism: The directional growth movement of a plant part in response to a chemical stimulus. Example: Growth of the pollen tube through the style towards the ovule attracted by chemical secretions. [1 Mark]
(b) Abscisic Acid (ABA) is the growth-inhibiting hormone that promotes wilting, leaf fall, and seed dormancy. [1 Mark]
(c) Mimosa pudica leaves show rapid turgor movement (seismonasty). Touching transmits an electrical-chemical signal causing the cells in the pulvinus (leaf base) to lose water rapidly, collapsing the cells and causing the leaflets to fold. [1 Mark]

Q12. Sex Determination in Humans: [3 Marks]

Human females possess two homomorphic sex chromosomes ($XX$), producing eggs carrying only $X$ chromosomes. [0.5 Mark]
Human males possess heteromorphic sex chromosomes ($XY$), producing two types of sperms in equal numbers (50% carrying $X$ and 50% carrying $Y$). [0.5 Mark]
Genetic Cross:
- Mother ($XX$) $\times$ Father ($XY$)
- Gametes: Eggs ($X$) $\times$ Sperms ($X$ or $Y$)
- $X + X \rightarrow XX$ (Female child, 50% chance)
- $X + Y \rightarrow XY$ (Male child, 50% chance) [1.5 Marks]
Thus, the sex of the child is determined purely by whether an $X$-bearing or $Y$-bearing sperm fertilises the ovum. [0.5 Mark]

Q13. Differences between Arteries and Veins: [3 Marks]

Feature	Artery	Vein
(a) Wall Thickness	Thick, muscular, and elastic walls to withstand high pumping pressure. [1 Mark]	Thin, less muscular, and flexible walls.
(b) Direction of Flow	Carries blood away from the heart to various body organs. [1 Mark]	Carries blood from various organs back towards the heart.
(c) Presence of Valves	Internal valves are absent (blood flows under high pressure). [1 Mark]	Internal pocket valves are present to prevent backward flow of blood.

Q14. Case-Based Solutions (Biology): [4 Marks]

(a) Pepsin (secreted as inactive pepsinogen). It requires an acidic medium (provided by hydrochloric acid, pH ~1.5–2.0) to be activated. [1 Mark]
(b) The large intestine absorbs excess water and salts from unabsorbed food material and stores undigested solid waste in the rectum prior to egestion. [1 Mark]
(c) Pancreatic juice roles: (i) Contains trypsin to break down proteins into peptides; (ii) Contains lipase to digest emulsified fats into fatty acids and glycerol; (iii) Contains pancreatic amylase to hydrolyse starch. [2 Marks]

OR (Role of Liver)

The liver secretes bile juice containing bile salts. Bile salts break down large, insoluble lipid droplets into microscopic droplets (a process called emulsification), dramatically increasing the surface area for pancreatic lipase enzymes. Bile also neutralises acidic stomach chyme to provide an alkaline pH for optimal enzyme action. [2 Marks]

Q15. Long Answer (Biology): [5 Marks]

(a) Nephron Diagram: Well-labelled diagram showing Bowman’s capsule, Glomerulus, Proximal Convoluted Tubule (PCT), Loop of Henle, Distal Convoluted Tubule (DCT), and Collecting duct. [2 Marks]
(b) Stages of Urine Formation:
- Glomerular Ultrafiltration: High blood pressure in the glomerulus forces water, urea, glucose, amino acids, and salts through the podocyte slits into the Bowman’s capsule as initial filtrate. [1 Mark]
- Tubular Reabsorption: Useful substances like glucose, amino acids, essential ions, and water are actively and selectively reabsorbed back into peritubular blood capillaries. [1 Mark]
- Tubular Secretion: Extra waste ions ($K^+$, $H^+$, ammonia) are actively secreted from capillary blood into the filtrate to regulate blood pH and ionic balance. [0.5 Mark]
(c) The urinary bladder acts as a muscular reservoir that temporarily stores urine until it is excreted under voluntary nervous control. [0.5 Mark]

(a) Budding in Hydra: A small regenerative outgrowth (bud) develops due to repeated mitotic cell divisions at a specific site $\rightarrow$ The bud grows into a miniature individual with tentacles and mouth $\rightarrow$ When fully mature, it detaches from the parent body to live independently. (Accompanying labelled diagrams). [2 Marks]
(b) Difference: Regeneration is the capacity of an organism to regrow lost or mutilated body parts from specialized cells, whereas reproduction is the biological mechanism of generating new independent progeny. Complex multi-cellular organisms have highly differentiated organ-system tissues and cannot recreate whole individuals from severed parts. [1.5 Marks]
(c) Advantages of Vegetative Propagation: (i) Plants raised this way bear flowers and fruits much earlier than those grown from seeds; (ii) Produces genetically identical offspring, preserving desirable crop traits; (iii) Allows propagation of seedless plants like banana, rose, and seedless grapes. [1.5 Marks]

SECTION B – CHEMISTRY SOLUTIONS

Q16. (c) Phenolphthalein [1 Mark]
Explanation: Phenolphthalein is a synthetic indicator that remains colourless in acidic and neutral solutions but turns deep pink/reddish-pink in basic (alkaline) solutions.

Q17. (b) Na₂CO₃ · 10H₂O [1 Mark]
Explanation: Washing soda is chemically sodium carbonate decahydrate, represented as $Na_2CO_3 \cdot 10H_2O$.

Q18. (c) Bromine [1 Mark]
Explanation: Bromine ($Br_2$) is the only non-metallic element that exists in a liquid state at room temperature.

Q19. (c) A carboxylic acid group (–COOH) [1 Mark]
Explanation: Ethanoic acid ($CH_3COOH$) belongs to the carboxylic acid homologous series and contains the $-COOH$ carboxyl functional group.

Q20. (b) Double displacement reaction [1 Mark]
Explanation: $BaCl_2(aq) + Na_2SO_4(aq) \rightarrow BaSO_4(s)\downarrow + 2NaCl(aq)$. Here, an exchange of ions between the two reactants forms an insoluble precipitate of barium sulphate.

Q21. (a) Both A and R are true and R is the correct explanation of A. [1 Mark]
Explanation: Pure 24-carat gold is extremely malleable and soft, making it prone to bending and scratching. It is typically alloyed with 2 parts of copper or silver (22-carat gold) to impart mechanical rigidity for jewellery.

Q22. Flushing Chips Bags with Nitrogen: [2 Marks]

Nitrogen is an unreactive, inert gas that displaces oxygen from the packet, preventing the oxidation of oils and fats present in the chips. [1 Mark]
The phenomenon prevented is Rancidity (which causes foul smell and bad taste in stale fatty foods). [1 Mark]

Q23. Chemical Equations: [3 Marks]

(a) $3MnO_2(s) + 4Al(s) \xrightarrow{\Delta} 3Mn(l) + 2Al_2O_3(s) + \text{Heat}$ [1 Mark]
(b) $3Fe(s) + 4H_2O(g) \rightarrow Fe_3O_4(s) + 4H_2(g)$ [1 Mark]
(c) $Ca(s) + 2H_2O(l) \rightarrow Ca(OH)_2(aq) + H_2(g)$ [1 Mark]

(a) Alloy: A homogeneous mixture of two or more metals, or a metal and a non-metal. [1 Mark]
- Brass: Copper (70%) + Zinc (30%). Used for making utensils, decorative hardware, and musical instruments. [1 Mark]
- Solder: Lead (50%) + Tin (50%). Has a low melting point; used for joining electrical wires. [0.5 Mark]
(b) Amalgam: An alloy in which one of the constituent metals is Mercury (e.g., sodium amalgam, dental amalgam). [0.5 Mark]

Q24. Covalent Bonding in Carbon: [3 Marks]

(a) Carbon has atomic number 6 (configuration 2, 4).
- It cannot gain 4 electrons to form $C^{4-}$ because it would be difficult for a nucleus with 6 protons to hold onto 10 electrons.
- It cannot lose 4 electrons to form $C^{4+}$ because it requires a huge amount of energy to remove 4 electrons from a tiny atom.
- Hence, carbon overcomes this problem by sharing its valence electrons with other atoms, forming stable covalent bonds. [2 Marks]
(b) Electron Dot Structure of Ethyne ($H-C\equiv C-H$):
$H : C ::: C : H$ (sharing 3 pairs of electrons between the two carbon atoms and 1 pair between each carbon and hydrogen). [1 Mark]

Q25. Case-Based Solutions (Chemistry): [4 Marks]

(a) Solution A (pH = 3) has a significantly higher concentration of $H^+$ ions (lower pH indicates higher acidity). [1 Mark]
(b) Distilled water is neutral (pH 7), so universal indicator paper turns green. [1 Mark]
(c) Excessive use of chemical fertilisers or acid rain can make agricultural soil overly acidic. Farmers add bases like quicklime ($CaO$) or slaked lime ($Ca(OH)_2$) to neutralise soil acidity and restore optimum pH for crop growth. [2 Marks]

OR (Antacids)

Antacids are mild, non-corrosive basic compounds. When ingested, they react with excess hydrochloric acid secreted in the stomach in a neutralisation reaction, reducing hyperacidity and relieving burning pain. [1 Mark]
Compounds: Magnesium hydroxide / Milk of Magnesia [$Mg(OH)_2$] and Sodium hydrogen carbonate [$NaHCO_3$]. [1 Mark]

Q26. Long Answer (Chemistry): [5 Marks]

(a) Cleansing Mechanism of Soap: A soap molecule has two parts: an ionic hydrophilic “head” that interacts with water and a long hydrocarbon hydrophobic “tail” that interacts with oily dirt. In water, soap molecules cluster into spherical structures called micelles where the hydrophobic tails point inward trapping oil droplets, while the ionic heads point outwards into water. When rinsed, the emulsified oil droplets are washed away. [2.5 Marks]
(b) Micelle Diagram: Neat drawing of a spherical micelle showing inward-pointing hydrocarbon tails surrounding an oil droplet and outward-pointing $COO^-Na^+$ heads interacting with water. [1.5 Marks]
(c) Hard water contains $Ca^{2+}$ and $Mg^{2+}$ ions. Soaps react with these ions to form an insoluble sticky precipitate (scum). Synthetic detergents do not form insoluble precipitates with $Ca^{2+}$ and $Mg^{2+}$ ions because their charged groups are sulphonates or sulphates, allowing them to remain effective in hard water. [1 Mark]

(a) Chemical Name: Calcium oxychloride. Formula: $CaOCl_2$. [1 Mark]
(b) Preparation: $Ca(OH)_2(s) + Cl_2(g) \rightarrow CaOCl_2(s) + H_2O(l)$ [1.5 Marks]
(c) Uses: (i) Bleaching cotton and linen in textile industries; (ii) Disinfecting drinking water to make it germ-free; (iii) As an oxidising agent in chemical laboratories. [1.5 Marks]
(d) When exposed to air, it reacts with atmospheric $CO_2$ and slowly loses chlorine: $CaOCl_2 + CO_2 \rightarrow CaCO_3 + Cl_2\uparrow$. [1 Mark]

Q27. Physical vs Chemical Change: [2 Marks]

Physical Change: Only the physical state, shape, or appearance changes; no new substance is formed, and the process is usually reversible. Example: Melting of ice / boiling of water. [1 Mark]
Chemical Change: Chemical bonds break and form to produce one or more entirely new substances with different chemical properties; generally irreversible. Example: Burning of magnesium ribbon / rusting of iron. [1 Mark]

SECTION C – PHYSICS SOLUTIONS

Q28. (c) 110° [1 Mark]
Explanation: Angle of reflection $r = i = 35^\circ$. Angle of deviation $\delta = 180^\circ – (i + r) = 180^\circ – (35^\circ + 35^\circ) = 180^\circ – 70^\circ = 110^\circ$.

Q29. (a) 4 Ω [1 Mark]
Explanation: Resistance is directly proportional to length ($R \propto L$). When the wire of original resistance $16\ \Omega$ is cut into 4 equal segments, the resistance of each segment becomes $R’ = \frac{16}{4} = 4\ \Omega$.

Q30. (b) Atmospheric refraction [1 Mark]
Explanation: Due to atmospheric refraction of light passing through layers of varying optical density, the Sun is visible about 2 minutes before the actual sunrise and for about 2 minutes after actual sunset.

Q31. (d) Is uniform at all points inside [1 Mark]
Explanation: The magnetic field lines inside a long current-carrying solenoid are straight, parallel, and equidistant, indicating that the magnetic field is uniform at all internal points.

Q32. (a) Both A and R are true and R is the correct explanation of A. [1 Mark]
Explanation: According to Rayleigh’s scattering law, scattering intensity is inversely proportional to the fourth power of wavelength ($I \propto \frac{1}{\lambda^4}$). Red has the longest visible wavelength and scatters the least, making it visible from long distances through fog and smoke.

Q33. (a) Both A and R are true and R is the correct explanation of A. [1 Mark]
Explanation: In parallel combination, $\frac{1}{R_p} = \frac{1}{R_1} + \frac{1}{R_2} + \dots$, which means the reciprocal of total resistance is the sum of reciprocals, making $R_p$ smaller than any individual resistor in the circuit.

Q34. Mirror Formula Calculation: [2 Marks]
Given: Concave mirror $\implies f = -20\text{ cm}$, $u = -12\text{ cm}$.
Using Mirror formula: $\frac{1}{f} = \frac{1}{v} + \frac{1}{u} \implies \frac{1}{v} = \frac{1}{f} – \frac{1}{u}$
$\frac{1}{v} = \frac{1}{-20} – \frac{1}{-12} = -\frac{1}{20} + \frac{1}{12} = \frac{-3 + 5}{60} = \frac{+2}{60} = \frac{1}{30}$
$\implies v = \mathbf{+30\text{ cm}}$. [1 Mark]
Nature: Since $v$ is positive, the image is formed 30 cm behind the mirror and is virtual and erect. [1 Mark]

Q35. Definition of 1 Volt: [2 Marks]

The electric potential difference between two points is said to be 1 Volt if 1 Joule of work is done in moving a unit positive charge of 1 Coulomb from one point to the other against electrostatic forces. [1 Mark]
Formula: $1\text{ Volt} = \frac{1\text{ Joule}}{1\text{ Coulomb}}$ ($V = \frac{W}{Q}$). [1 Mark]

OR
Given: $I = 0.5\text{ A}$, $t = 10\text{ min} = 10 \times 60 = 600\text{ s}$.
Electric charge $Q = I \times t$ [1 Mark]
$Q = 0.5\text{ A} \times 600\text{ s} = \mathbf{300\text{ C}}$. [1 Mark]

Q36. Tyndall Effect: [3 Marks]

(a) Definition: The phenomenon of scattering of a beam of light by colloidal or fine suspended particles in its path, making the path of the light beam visible. [1 Mark]
(b) Examples: (i) When a fine beam of sunlight enters a smoke-filled room through a small hole; (ii) When sunlight passes through the canopy of a dense forest containing mist droplets. [1 Mark]
(c) The fine colloidal particles have sizes comparable to the shorter wavelength of blue light. Hence, they scatter blue light much more strongly than longer-wavelength red light. [1 Mark]

Q37. Electric Generator and AC vs DC: [3 Marks]

Principle: An electric generator works on the principle of Electromagnetic Induction (Faraday’s Law) — when a closed coil is rotated in a magnetic field, magnetic flux linked with it changes, inducing an electric current. [1 Mark]
AC vs DC:
- Alternating Current (AC): Electric current that periodically reverses its direction of flow at regular intervals of time (frequency in India is 50 Hz). [1 Mark]
- Direct Current (DC): Electric current that flows consistently in only one direction with constant polarity. [1 Mark]

Q38. Case-Based Solutions (Physics): [4 Marks]

(a) Electric Power: The rate at which electrical energy is consumed or dissipated in an electric circuit. SI unit: Watt (W). [1 Mark]
(b) $R = \frac{V^2}{P} = \frac{(220)^2}{100} = \frac{48400}{100} = \mathbf{484\ \Omega}$. [1 Mark]
(c) Energy consumed daily $= P \times t = 100\text{ W} \times 5\text{ h} = 500\text{ Wh} = 0.5\text{ kWh}$.
Total energy consumed in 30 days $= 0.5\text{ kWh/day} \times 30\text{ days} = \mathbf{15\text{ kWh}}$ (15 units). [2 Marks]

OR (Alternative Parallel Current Calculation)

Current drawn by 1st lamp: $I_1 = \frac{P_1}{V} = \frac{100\text{ W}}{220\text{ V}} \approx 0.455\text{ A}$ [1 Mark]
Current drawn by 2nd lamp: $I_2 = \frac{P_2}{V} = \frac{60\text{ W}}{220\text{ V}} \approx 0.273\text{ A}$ [0.5 Mark]
Total current drawn from line: $I_{\text{total}} = I_1 + I_2 = \frac{100 + 60}{220} = \frac{160}{220} \approx \mathbf{0.73\text{ A}}$. [0.5 Mark]

Q39. Long Answer (Physics): [5 Marks]

(a) Convex Mirror Numerical:
Given: Radius of curvature $R = +3.00\text{ m} \implies f = +\frac{3.00}{2} = +1.50\text{ m}$.
Object distance $u = -5.00\text{ m}$.
Mirror formula: $\frac{1}{f} = \frac{1}{v} + \frac{1}{u} \implies \frac{1}{v} = \frac{1}{1.50} – \frac{1}{-5.00} = \frac{1}{1.50} + \frac{1}{5.00} = \frac{10}{15} + \frac{1}{5} = \frac{2}{3} + \frac{1}{5} = \frac{13}{15}$
$\implies v = +\frac{15}{13}\text{ m} \approx \mathbf{+1.15\text{ m}}$. (Image is formed 1.15 m behind the mirror). [1.5 Marks]
Magnification: $m = -\frac{v}{u} = -\frac{+1.15}{-5.00} = \mathbf{+0.23}$.
Nature: Virtual, erect, and diminished (reduced by a factor of 0.23). [1 Mark]
(b) Power of Lens: The reciprocal of its focal length expressed in metres ($P = \frac{1}{f\text{ (in m)}}$). [1 Mark]
Given: $P = +1.5\text{ D} \implies f = \frac{1}{P} = \frac{1}{+1.5} = +\frac{10}{15}\text{ m} = \mathbf{+0.67\text{ m}}$ (or $+66.7\text{ cm}$). [1 Mark]
Since the focal length and power are positive, it is a converging (convex) lens. [0.5 Mark]

(a) Bar Magnet Field Lines & Properties:
- Neat diagram showing continuous closed magnetic loops emerging from the North pole and merging at the South pole outside the magnet, and directed from South to North inside the magnet. [1.5 Marks]
- Properties: (i) Magnetic field lines are closed continuous curves; (ii) The degree of closeness of field lines indicates the relative magnetic field strength; (iii) No two magnetic field lines ever intersect each other. [1.5 Marks]
(b) Force on Current-Carrying Conductor:
- Setup: Suspend a small aluminium rod horizontally between the poles of a strong horseshoe magnet using connecting wires connected in series with a battery, key, and rheostat. [1 Mark]
- Observation: When current is passed through the rod from one end to the other, the rod gets visibly deflected sideways. Reversing the direction of current reverses the direction of mechanical displacement, demonstrating that a magnetic force acts on a current-carrying conductor in a magnetic field. [1 Mark]

CBSE Class X Science • Sample Paper Set 7 with Complete Solutions • Academic Session 2026–2027

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