Question Paper

CBSE Class 10 Science Sample Paper 2027 – Set 3

Time allowed: 3 hours · Maximum marks: 80

General Instructions

1. This question paper contains 39 questions. All questions are compulsory.
2. The question paper is divided into THREE sections: Section A - Biology (30 marks), Section B - Chemistry (25 marks) and Section C - Physics (25 marks).
3. The question paper has MCQs, VSAs, SAs, LAs and CBQs. Marks are given against each question.
4. There are Case Based Questions (CBQs) with three sub-questions, of 4 marks each.
5. Divide your answer sheet into three sections as per the question paper: Section A (Biology), Section B (Chemistry) and Section C (Physics). Answer each question in its own section, and do not mix answers of one section with another.
6. Instructions are given with each section and question, wherever necessary.
7. There is no overall choice in the question paper. However, an internal choice has been provided in a few questions. Only one of the choices in such questions must be attempted.

How to use this paper: set a 3-hour timer and write all your answers on paper, just like the board exam. When you finish, take the quiz at the end of this page to score your objective (MCQ) answers instantly, then open the Detailed Solutions and check the rest step by step, with the marks each step carries.

Section A - Biology (30 marks)

Questions 1 to 7 are multiple choice questions and questions 8 and 9 are Assertion-Reason questions, of 1 mark each. Questions 10 to 12 carry 2 marks each, questions 13 and 14 carry 3 marks each, question 15 is a case based question of 4 marks and question 16 is a long answer question of 5 marks.

1. Read the following statements about how plants get rid of their waste products.

(i) Plants get rid of excess water by transpiration.
(ii) Some waste products are stored in leaves, which later fall off.
(iii) Gums and resins are stored mainly in the young, actively dividing cells at the tips of roots and shoots.
(iv) Some wastes are stored in cell vacuoles, and some are released into the soil around the plant.

Which of these statements are correct?

(a) (i) and (ii) only
(b) (ii) and (iii)
(c) (i), (ii) and (iv)
(d) (i), (iii) and (iv)

2. Anjali kept two potted plants of the same kind in a dark room for three days. She then placed each pot on a glass plate and covered it with a bell jar, sealing the bottom of each jar with vaseline. In jar Y she also kept a watch glass P containing potassium hydroxide solution, as shown in the figure. Both jars were kept in sunlight for six hours, and then one leaf from each plant was tested with iodine solution. Which option gives the correct result and the correct reason?

(a) Only the leaf from X turns blue-black, because potassium hydroxide in Y absorbs carbon dioxide.
(b) Only the leaf from Y turns blue-black, because potassium hydroxide in Y absorbs the extra moisture that slows down photosynthesis.
(c) Both leaves turn blue-black, because both plants received sunlight, water and chlorophyll.
(d) Only the leaf from X turns blue-black, because potassium hydroxide in Y absorbs the oxygen given out by the plant.

3. Leishmania and Plasmodium are both single-celled parasites. Which statement about the way they reproduce is correct?

(a) Both divide by multiple fission: the nucleus divides many times over, and the cell then breaks up into many daughter cells at once.
(b) Leishmania breaks up into many daughter cells at once by multiple fission, while Plasmodium splits into two equal halves by binary fission.
(c) Both reproduce by budding, in which a small outgrowth forms on the parent cell, grows for a while and then separates to live on its own.
(d) Leishmania splits into two in a definite plane, set by its whip-like structure, while Plasmodium divides into many daughter cells at once.

4. Priya left a piece of moist bread in a warm, dark cupboard. After a few days, a white cotton-like growth with tiny black dots appeared on it. Under a magnifying glass, each black dot was seen at the tip of a thin, thread-like stalk. What are the black dots, and why do they help the fungus to spread?

(a) They are seeds of the fungus; being heavy, they drop straight down onto any food lying close to the bread and grow there.
(b) They are sporangia full of spores; the spores have thick walls and survive until they land on a moist surface.
(c) They are buds formed on the threads; each one breaks off its stalk and grows into a new fungus wherever it falls.
(d) They are male and female gametes; they are carried by air, fuse with each other and form a zygote that grows into a new fungus.

5. While walking home at dusk, Arjun is suddenly chased by a barking dog. His adrenal glands release adrenaline. Consider these statements:

(i) Adrenaline is carried by the blood to its target organs, including the heart.
(ii) His heart beats faster, so that more oxygen is supplied to his muscles.
(iii) Less blood goes to the digestive system and the skin, and more goes to the skeletal muscles.
(iv) Adrenaline is poured into a duct that carries it straight to the heart.

Which statements are correct?

(a) (i), (ii) and (iii)
(b) (ii) and (iv)
(c) (i), (iii) and (iv)
(d) (ii) and (iii) only

6. Mendel carried out his experiments on the garden pea. Which statement was NOT a reason why the pea plant suited his work?

(a) It shows many clearly visible contrasting traits, such as tall and short plants, or round and wrinkled seeds.
(b) The F1 plants could simply be left to self-pollinate, which gave him the F2 generation.
(c) Its flowers cannot be cross-pollinated, so he could never cross two different plants.
(d) Its offspring fall into clear groups, such as tall or short, which he could count to work out percentages.

7. Ozone in the upper atmosphere is formed in two steps: $\mathrm{O_2 \rightarrow O + O}$ and then $\mathrm{O + O_2 \rightarrow O_3}$. Which option is correct?

(a) The first step is caused by infrared radiation from the Sun, and the ozone layer is being thinned mainly by carbon dioxide from burning coal and petrol.
(b) The first step is caused by ultraviolet radiation, and the ozone layer has been thinned mainly by CFCs, used as refrigerants and in fire extinguishers.
(c) Three separate oxygen atoms join together at once to form ozone, and CFCs from refrigerators slowly help to rebuild the ozone layer.
(d) The first step is caused by visible light, and the ozone layer is being thinned mainly by methane given off by paddy fields and cattle.

Directions: Questions 8, 9, 24 and 32 each consist of two statements, Assertion (A) and Reason (R). Answer these questions by selecting the appropriate option (a), (b), (c) or (d) given with each.

8. Assertion (A): When we touch a very hot plate by mistake, we pull our hand back at once, without thinking about it.

Reason (R): The spinal cord is protected by the bony vertebral column.

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

9. Assertion (A): In a food chain, the number of individuals always increases as we go to higher trophic levels.

Reason (R): At each trophic level, a large part of the energy is used up in the organisms' own life processes, so less energy is available to the next level.

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

10. Answer the following:

(a) Desert plants such as cactus keep their stomata closed during the day and open them at night. Why? How do they manage to photosynthesise during the day? (1 mark)

(b) ATP is called the energy currency of the cell. What does this mean? Name one activity in the body that uses it. (1 mark)

11. Farida crossed pure-breeding pea plants that were tall with green pods with pure-breeding plants that were dwarf with yellow pods. All the F1 plants were tall with green pods. When the F1 plants self-pollinated, the F2 generation had four kinds of plants, including some that were tall with yellow pods and some that were dwarf with green pods. Give the expected ratio of the four kinds of F2 plants. How do these results show that the two traits are inherited independently? (2 marks)

12. Attempt either option (A) or (B).

(A) A doctor tells a woman in the third month of pregnancy that the placenta has formed well. What is the placenta? Name two things that pass through it from the mother to the embryo, and one thing that passes the other way. (2 marks)

OR

(B) Sunaina is four months pregnant. Her doctor tells her to eat regular, balanced meals and not to go without food, because "whatever the baby gets, it gets from your meals". Trace how the food she eats reaches the growing embryo. Why can the embryo not get its food in any other way?

13. Ritika crossed pure-breeding pea plants with violet flowers and pure-breeding plants with white flowers. All the F1 plants had violet flowers. She let the F1 plants self-pollinate and counted the flowers on the F2 plants:

(a) Which trait is dominant? Work out the F2 ratio from the table. (1 mark)

(b) Using V for the dominant gene and v for the recessive one, show the cross between two F1 plants and write the genotype ratio of the F2 plants. (1 mark)

(c) About how many of the 450 violet F2 plants are expected to be pure-breeding (VV)? If a white F2 plant is self-pollinated, what colour flowers will its offspring have? Give a reason. (1 mark)

14. A wheat field in a village near Hisar has the food chain: wheat → rat → snake → eagle. The figure shows its pyramid of energy, with the levels marked P, Q, R and S from the bottom.

(a) Why is a crop field called an artificial ecosystem? Which organism is at level R, and which trophic level is it? (1 mark)

(b) The wheat plants in the field store 60,000 kJ of energy as food. Using the 10 per cent law, find the energy available to the snakes and to the eagles. (1 mark)

(c) Karan says, "When an eagle dies in the field, decomposers break down its body, and the energy stored in it goes back to the wheat. So energy keeps going round and round in this field." Is Karan right? Give a reason. (1 mark)

15. Tanvi's class in a school in Bhopal set up two activities. In the first, a few germinating bean seeds were pressed between wet cotton wool and the inside wall of a clear glass jar, so that they could be seen, and the jar was laid on its side in a dark cupboard. After three days, the shoots had curved upwards and the roots had curved downwards. In the second, bean seedlings were kept in a closed cardboard box that had a narrow slit on one side, facing a window. After a few days, all the shoots had bent towards the slit. Their teacher explained that a plant hormone made at the tip of the shoot is responsible for this bending.

(a) Name the movement shown by the shoots in the second activity, and the hormone responsible. (1 mark)

(b) In the first activity, which part shows positive geotropism and which shows negative geotropism? (1 mark)

(c) Explain how the hormone makes the shoots bend towards the slit. The first slit is now closed and a new slit is cut in the opposite side of the box, which is turned so that the new slit faces the window. What will happen to the shoots over the next few days? (2 marks)

OR

(c) Why do the root and the shoot respond to gravity in opposite ways? Why did the class keep the jar of the first activity in a dark cupboard and not near the window? (2 marks)

16. Attempt either option (A) or (B).

(A) In human beings, the heart keeps oxygen-rich and oxygen-poor blood completely apart.

(i) Draw a schematic sectional view of the human heart and label any four of these: right atrium, right ventricle, left atrium, left ventricle, aorta. Which chamber has the thickest muscular wall, and why? (3 marks)

(ii) What is meant by double circulation? Why is it important for birds and mammals that the oxygenated and deoxygenated blood do not mix? (2 marks)

OR

(B) Harpreet covered the leafy shoot of a potted balsam plant with a clear polythene bag and tied it round the base of the stem, so that the soil stayed outside the bag. She kept the pot in sunlight. After a few hours, drops of water appeared on the inside of the bag.

(i) Name the process that produced the drops. Why did she keep the soil outside the bag? Explain how this process helps water to rise to the top of a tall tree, and give one other use of this process to the plant. (3 marks)

(ii) Give two differences between the transport of food in the phloem (translocation) and the transport of water in the xylem. (2 marks)

Section B - Chemistry (25 marks)

Questions 17 to 23 are multiple choice questions and question 24 is an Assertion-Reason question, of 1 mark each. Question 25 carries 2 marks, questions 26 and 27 carry 3 marks each, question 28 is a case based question of 4 marks and question 29 is a long answer question of 5 marks.

17. Neha noted five changes at home on a winter morning:

(i) Milk had set into curd overnight.
(ii) Sugar dissolved in her tea.
(iii) A brown, flaky layer had formed on the iron gate after the rains.
(iv) Ghee in a tin melted when it was kept near the stove.
(v) The gas burned in the stove.

Which of these are chemical changes?

(a) (i) and (ii)
(b) (ii), (iv) and (v)
(c) (iii) and (iv)
(d) (i), (iii) and (v)

18. A worker from the municipal board adds bleaching powder to the overhead water tank of a housing society. Four residents who are watching make these remarks. Whose remark is NOT correct?

(a) Meera: "Now the water will become soft, and soap will give a good lather with it."
(b) Joseph: "It is added to kill the germs in it, so that the water becomes safe to drink."
(c) Ayaan: "The same powder is used in textile mills to bleach cotton and linen."
(d) Kiran: "It is also used as an oxidising agent in many chemical industries."

19. In a molecule of propane, $\mathrm{C_3H_8}$, the three carbon atoms form an open chain. In a molecule of cyclopropane, $\mathrm{C_3H_6}$, the three carbon atoms are joined in a ring, and every bond is a single bond. How many covalent bonds are there in one molecule of each?

(a) Propane 10; cyclopropane 8
(b) Propane 11; cyclopropane 9
(c) Propane 10; cyclopropane 9
(d) Propane 10; cyclopropane 10

20. Rhea set up a circuit with a battery, a bulb and two graphite rods dipping into a beaker. She tested equal volumes of dilute hydrochloric acid and dilute acetic acid of the same concentration, one after the other. What will she observe?

(a) The bulb glows equally brightly in both, since both of them are acids, and every acid gives hydrogen ions in the same way when it is dissolved in water.
(b) The bulb glows brightly in hydrochloric acid but only dimly in acetic acid, since hydrochloric acid gives many more $\mathrm{H^+}$ ions in water.
(c) The bulb glows dimly in hydrochloric acid and brightly in acetic acid, since each molecule of acetic acid has more hydrogen atoms to give.
(d) The bulb does not glow in either, since both acids are made of covalent molecules and so cannot conduct electricity at all.

21. The structural formula of an organic compound is shown. Which option gives its molecular formula and describes it correctly?

(a) $\mathrm{C_6H_6}$; unsaturated, because the six carbon atoms are joined up to form a closed ring
(b) $\mathrm{C_6H_{14}}$; saturated, because each carbon atom is joined to the next by a single bond
(c) $\mathrm{C_6H_{12}}$; unsaturated, because it has the same formula as hexene
(d) $\mathrm{C_6H_{12}}$; saturated, because all the carbon-carbon bonds are single bonds

22. Match the reactions in Column I with their types in Column II.

(a) P-2, Q-4, R-1, S-3
(b) P-2, Q-1, R-4, S-3
(c) P-4, Q-2, R-3, S-1
(d) P-2, Q-4, R-3, S-1

23. Which of the following statements about exceptions to the usual properties of metals and non-metals are correct?

(i) Iodine is a non-metal, but it is lustrous.
(ii) Graphite, a form of carbon, is a good conductor of electricity.
(iii) Mercury is a metal that is a liquid at room temperature.
(iv) Sodium and potassium are metals so hard that they cannot be cut with a knife.

(a) (ii) and (iii) only
(b) (i), (ii) and (iii)
(c) (iii) and (iv)
(d) (i), (ii) and (iv)

24. Assertion (A): Aluminium is widely used for making cooking utensils.

Reason (R): Aluminium is a poor conductor of heat.

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

25. Answer the following:

(a) Draw the electron dot structure of a molecule of carbon dioxide, $\mathrm{CO_2}$. (Atomic numbers: C = 6, O = 8) (1 mark)

(b) Dry ice (solid carbon dioxide) does not conduct electricity, but soda water, which is carbon dioxide dissolved in water under pressure, conducts it slightly. Explain both observations. (1 mark)

26. Attempt either option (A) or (B).

(A) Sonal dropped a small piece of sodium into a test tube containing a little absolute ethanol.

(i) Write the balanced chemical equation for the reaction and name the organic product. (1 mark)

(ii) How can she test the gas given off? (1 mark)

(iii) Ethanol is also used as a fuel. Write the balanced chemical equation for its complete combustion, and say what kind of flame it gives. (1 mark)

OR

(B) Sonal took 1 mL of ethanol and 1 mL of glacial ethanoic acid in a test tube, added a few drops of concentrated sulphuric acid and warmed the tube in a water bath for five minutes. She then poured the mixture into a beaker of water.

(i) What has Sonal made? Give the equation for its formation, the name of the organic product and the class of compounds it belongs to. (1 mark)

(ii) How can Sonal tell, after pouring the mixture into water, that the product has formed? What is the job of the sulphuric acid? (1 mark)

(iii) Her friend says, "This is just a neutralisation, like an acid reacting with sodium hydroxide, because ethanol is a base." Is the friend right? Give a reason. (1 mark)

27. Tanya mixed the following pairs of solutions in three test tubes:

P: silver nitrate solution and sodium chloride solution
Q: copper sulphate solution and sodium hydroxide solution
R: potassium nitrate solution and sodium chloride solution

(a) In tube P a precipitate forms. Write the balanced chemical equation and give the colour and name of the precipitate. (1 mark)

(b) In tube Q a precipitate also forms. Write the balanced chemical equation and give the colour and name of the precipitate. (1 mark)

(c) The mixture in tube R stays clear. Why is no precipitate formed? Name the type of reaction that took place in P and Q. (1 mark)

28. During the holidays, Rupa helped at her uncle's bakery in Kolkata, where baking soda is used to make cakes soft and spongy. At home, her mother cleans greasy vessels with hot water in which washing soda has been dissolved. The same week, Rupa's brother fractured his wrist. In the plaster room of the hospital, the wrist was wrapped in a bandage coated with a white powder mixed with water, which set into a hard cast within minutes. This white powder is Plaster of Paris, $\mathrm{CaSO_4 \cdot \frac{1}{2}H_2O}$.

(a) Which gas makes the cake rise? Write the chemical equation for the reaction that gives this gas when baking soda is heated. (1 mark)

(b) Will the solution of washing soda have a pH more than 7 or less than 7? Give a reason based on the acid and the base from which washing soda is formed. (1 mark)

(c) What does '$\frac{1}{2}\mathrm{H_2O}$' in the formula of Plaster of Paris stand for? Plaster of Paris is made by heating gypsum carefully at about 373 K. One batch was heated far more strongly by mistake, and the powder obtained did not set at all when it was mixed with water. Explain why, and write the chemical equation for the setting of good Plaster of Paris. (2 marks)

OR

(c) Rupa's uncle uses baking powder, which is baking soda mixed with a mild edible acid such as tartaric acid, instead of baking soda alone. What would go wrong if he used only baking soda? How does the acid prevent this? (2 marks)

29. Attempt either option (A) or (B).

(A) Ionic compounds are formed by the transfer of electrons from a metal to a non-metal.

(i) Write the electronic configurations of sodium (atomic number 11), chlorine (17), magnesium (12) and oxygen (8). Show, using electron dot structures, the formation of sodium chloride and of magnesium oxide by the transfer of electrons. (3 marks)

(ii) The table gives the melting and boiling points of four substances W, X, Y and Z.

Which two of these are likely to be ionic compounds? Give a reason. Which substance is a liquid at room temperature (25 °C)? (2 marks)

OR

(B) Kavita's teacher gave her these observations on three metals, P, Q and R, and asked her to decide how each metal could be obtained from its compounds.

(i) Arrange P, Q and R in decreasing order of reactivity, using the evidence in the table. Which of the three could also be found in the free state in nature? How should P be obtained from its compounds, and why can carbon not be used for it? (3 marks)

(ii) Highly reactive metals can also be used as reducing agents.

(I) Kavita heats the oxide of Q with powdered P. Can she get the metal Q in this way? Give a reason.
(II) Manganese is obtained by heating manganese dioxide with aluminium powder. Write the balanced chemical equation for the reaction and name the reducing agent. (2 marks)

Section C - Physics (25 marks)

Questions 30 and 31 are multiple choice questions and question 32 is an Assertion-Reason question, of 1 mark each. Questions 33 and 34 carry 2 marks each, questions 35 to 37 carry 3 marks each, question 38 is a case based question of 4 marks and question 39 is a long answer question of 5 marks.

30. Consider the following statements about the human eye.

(i) For a young adult with normal vision, the least distance of distinct vision is about 25 cm.
(ii) Cataract, in which the eye lens becomes milky and cloudy, is corrected by using bifocal lenses.
(iii) The near point of the eye usually moves farther away as a person grows old.
(iv) The far point of a normal eye is at infinity.

Which statements are correct?

(a) (i) and (ii)
(b) (ii), (iii) and (iv)
(c) (i) and (iv) only
(d) (i), (iii) and (iv)

31. Dev hung a thick copper wire vertically through a hole in a wooden bench. He placed four small compasses on the bench at equal distances to the east, north, west and south of the wire, and passed a large current downwards through the wire. Close to the wire, the effect of the Earth's magnetism can be ignored. Consider these statements about the north ends of the compass needles:

(i) The needle to the east of the wire points towards the south.
(ii) The needles to the north and to the south of the wire point in opposite directions.
(iii) The needle to the west of the wire points straight towards the wire.
(iv) Seen from above, the four needles point round the wire in an anticlockwise direction.

Which statements are correct?

(a) (ii) and (iii)
(b) (i), (ii) and (iv)
(c) (i) and (ii) only
(d) (i), (iii) and (iv)

32. Assertion (A): When a film is shown in a dusty school hall, the beam of light going from the projector to the screen can be seen clearly from the side.

Reason (R): The fine dust particles in the air scatter the light, and some of the scattered light reaches our eyes.

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

33. The refractive index of water is $\frac{4}{3}$ and that of a certain kind of glass is $\frac{3}{2}$, both with respect to air.

(a) Find the refractive index of this glass with respect to water. Which of the two is optically denser? (1 mark)

(b) A ray of light travelling in water falls on the glass surface such that $\sin i = 0.9$. Using Snell's law, find $\sin r$ in the glass. Does the ray bend towards or away from the normal? (1 mark)

34. Attempt either option (A) or (B).

(A) A torch bulb draws a current of 0.3 A when it is connected to a 4.5 V battery. Assume that its resistance stays the same.

(I) Find the current it will draw if it is connected to a 6 V battery instead. (1 mark)

(II) Will the bulb glow more or less brightly on the 6 V battery? Justify by comparing the power in the two cases. (1 mark)

OR

(B) Wires P and Q are both made of copper. Wire Q is twice as long as wire P and has twice the diameter of P.

(I) Find the ratio of the resistance of Q to that of P. (1 mark)

(II) The same potential difference is applied across each wire in turn. Which wire carries the larger current, and how many times larger is it? (1 mark)

35. Ayesha, a Class 7 student, sees distant objects clearly, but the words in her book look blurred when she holds it at the usual reading distance of 25 cm. Her eye doctor says she has hypermetropia.

(a) State two possible causes of this defect. (1 mark)

(b) Draw ray diagrams to show (i) where the image of a book held at the normal near point N is formed in Ayesha's eye, and (ii) how the correct spectacle lens lets her read it clearly. Mark the near point N′ of her eye in (ii). (2 marks)

36. Answer the following:

(a) In a school laboratory, a coil of resistance wire dipped in a beaker of water is used as a small immersion heater. When the current through the same coil is doubled, keeping the time the same, Asif says the heat produced will double. Is he right? Justify. (1 mark)

(b) Farhan is making a small toaster for a science fair. He wants to wind its heating coil from copper wire, "because copper conducts electricity so well". Is this a good choice? Give two reasons. (1 mark)

(c) Farhan then suggests using nichrome wire for the wiring of his house, "so that the wires never melt". What would go wrong? Why are copper wires used instead? (1 mark)

37. Mohit built the circuit shown on a board in the physics laboratory. The key K is closed.

(a) What single resistor could replace all three without changing the battery current? What current flows through the 3 Ω resistor? (1 mark)

(b) What is the voltage across the part XY? How is the battery current shared between the 4 Ω and 12 Ω resistors? (1 mark)

(c) Mohit says, "The 12 Ω resistor will produce the most heat every second, because it has the largest resistance." Is he right? Justify by finding the power in each resistor. (1 mark)

38. Mandi Gobindgarh in Punjab is known for its steel re-rolling mills. In a scrap yard there, a crane lifts heavy iron scrap with a large electromagnet: a thick coil of insulated copper wire wound on a soft-iron core. When the operator switches the current on, the magnet picks up a load of iron scrap; when she switches it off, the load drops. Aluminium cans and pieces of copper wire lying in the same heap are left behind.

(a) Why is the core made of soft iron and not of steel? (1 mark)

(b) Why are the aluminium cans and copper wires not lifted? (1 mark)

(c) Suggest two ways to make the crane lift heavier loads. What will happen to the poles of the electromagnet if the direction of the current in the coil is reversed? Will it still lift iron scrap? (2 marks)

OR

(c) Looking at the lower face of the electromagnet from below, the operator sees the current flowing clockwise in the coil. Use the right-hand thumb rule to find whether this face is a north or a south pole. Why is the coil made of many turns rather than a single loop? (2 marks)

39. Attempt either option (A) or (B).

(A) In the physics laboratory, Swati places a small candle 20 cm in front of a concave mirror of focal length 15 cm and moves a screen until she gets a sharp image of the flame.

(i) Where must the screen be placed? (1 mark)

(ii) Work out the magnification. Is the image real or virtual, erect or inverted, larger or smaller? (1 mark)

(iii) Give two uses of concave mirrors in daily life. (1 mark)

(iv) Using two rays from the tip of the flame, draw a ray diagram to show where the mirror forms its image. (2 marks)

OR

(B) A convex lens of focal length 12 cm forms an image of an object placed 36 cm in front of it.

(i) Find the position of the image. (1 mark)

(ii) How large is the image compared with the object? Is it real or virtual, and erect or inverted? Use the magnification. (1 mark)

(iii) Define the power of a lens and give its SI unit. A second convex lens has a power of +5 D. Find its focal length, and say which of the two lenses converges light more strongly. (1 mark)

(iv) Draw a ray diagram, using two rays from the top of the object, to show where this lens forms the image. (2 marks)