\u00a0 V (volts)<\/strong><\/td>\n| \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 1.6<\/td>\n | \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 3.4<\/td>\n | \u00a0\u00a0\u00a0\u00a0\u00a0 6.7<\/td>\n | \u00a0\u00a0\u00a0\u00a0 10.2<\/td>\n | \u00a0\u00a0\u00a0\u00a0 13.2<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n Plot a graph between V and I.<\/p>\n OR<\/strong><\/p>\nDraw a circuit diagram to show three resistors connected in series with a cell and a key. Write formula for the equivalent resistance R of this combination if the individual resistances of the resistors are R1<\/sub>, R2<\/sub> and R3<\/sub>.<\/p>\nQuestion 27.<\/strong>
\nIf you focus the image of a distant object whose shape is given below, on a screen using a convex lens. [2]<\/strong>
\n![\"CBSE](\"https:\/\/i2.wp.com\/www.ncert-solutions.com\/wp-content\/uploads\/2018\/10\/CBSE-Sample-Papers-for-Class-10-SCIENCE-Set-1-3.png?resize=102%2C109&ssl=1\")
\nThe shape of the image of this object on the screen would be:
\n![\"CBSE](\"https:\/\/i0.wp.com\/www.ncert-solutions.com\/wp-content\/uploads\/2018\/10\/CBSE-Sample-Papers-for-Class-10-SCIENCE-Set-1-4.png?resize=530%2C215&ssl=1\") <\/p>\nANSWERS<\/strong><\/span>
\nSECTION-A<\/strong><\/p>\nAnswer 1.<\/strong>
\nCell respiration can be defined as the biological oxidation of food taking place partly in the cytoplasm and partly in the mitochondria of the cell. During this oxidation, carbon dioxide and water are formed with the release of energy. This energy is stored in the cell as ATP-Adenosine Tri-Phosphate which is used when required to perform the various activities of the body.<\/p>\nAnswer 2.<\/strong>
\nThe Ganga Action Plan came into being in the year 1985. This multi-crore project came into being because the quality of water in the Ganga was very poor. Coliform bacteria, found in human intestine and whose presence indicates contamination by disease causing micro-organisms were found here. There were other dangerous contaminants too.<\/p>\nAnswer 3.<\/strong>
\nThe curry might contain turmeric powder which is the indicator of acids and bases. Soap being basic in nature turns the colour of the turmeric from yellow to reddish brown. After washing with lot of water the soap is removed and the turmeric returns of its yellow colour.<\/p>\nAnswer 4.<\/strong>
\nThe human eye is the most valuable and sensitive sense organ in our body. It helps us to see the wonderful and colourful world around us. If we close our eyes we can identify objects by their smell, sound, taste and feel. We can identify colours only by seeing them. The eye is like a camera. Its lens forms an image on the light-sensitive screen called retina. The ciliary muscles adjust the focal length of the lens so that wherever the object is placed, the image is always formed on the retina. The pupil regulates and controls the amount of light entering the eye. The precious eyes are protected by being placed in hollows of the skull called orbits.<\/p>\nAnswer 5.<\/strong>
\nIn any ecosystem we find several organisms interacting with one another. The process of different types of organisms feeding on one another constitutes a food-chain. Each step of the food chain is called a trophic level. Green plants which trap solar energy and prepare food are called producers. They are eaten by the herbivores which are called primary consumers. These are further eaten by small carnivores which are called secondary consumers. They in turn are eaten by big consumers called tertiary consumers.<\/p>\nAnswer 6.<\/strong>
\n(a) Copper and aluminium wires are used as connecting wires because they have low resistivity and are good conductors of electricity.
\n(b) Lead-tin alloy is used for making fuse wires because it has low melting point.
\n(c) Tungsten has high melting point and has great tensile strength so it is used as a filament in electric lamps.<\/p>\nOR<\/strong><\/p>\n![\"CBSE](\"https:\/\/i0.wp.com\/www.ncert-solutions.com\/wp-content\/uploads\/2018\/10\/CBSE-Sample-Papers-for-Class-10-SCIENCE-Set-1-5.png?resize=309%2C346&ssl=1\") (a) The strength of a magnetic field is inversely proportional to the square of the distance from the conductor i.e., the strength of the electric field decreases with increase in distance.
\n(b) The strength of the magnetic field is directly proportional to the current passing in the wire i.e., strength of the magnetic field increases with increase in current.<\/p>\n
Answer 7.<\/strong>
\nThe person is suffering from an eye defect called myopia. In this defect, the image is formed in front of the retina. Hence, a concave lens is used to correct this defect of vision.
\nThe object distance (\u03bc) = \u221e
\nThe image distance (\u03c5) = – 80 cm = – 0.8 m
\nUsing the formula,
\n\\(\\frac { 1 }{ \\upsilon } -\\frac { 1 }{ u } =\\frac { 1 }{ f }\\)
\nSubstituting the values, we get
\n\\(\\frac { -1 }{ 0.8 } -\\frac { 1 }{ \\infty } =\\frac { 1 }{ f } \\)
\n\\(\\frac { -1 }{ 0.8 } -0=\\frac { 1 }{ f } \\quad \\)
\n\\(\\frac { 1 }{ f } =\\frac { -1 }{ 0.8 } =-1.25D \\)
\nA concave lens of power -1.25 D is required by the person to correct his defect.<\/p>\nAnswer 8.<\/strong>
\n(a)<\/strong> (i) Zinc
\n(ii) Aluminium
\n(iii) Magnesium
\n(iv) Mercury<\/p>\n(b)<\/strong> (i) ZnO + C\u2192 Zn + CO
\n(ii) 3MgO + 2Al\u2192 3Mg + Al03<\/p>\nAnswer 9.<\/strong>
\nWhenever an acid reacts with a base it results in the formation of a salt and water and this is called neutralisation reaction.<\/p>\nAcid + Base = Salt + Water
\nNaOH(aq) + HCl(aq)\u2192 NaCl(aq)+ H2<\/sub>O(1)<\/p>\nIn the above case when sodium hydroxide reacts with hydrochloric acid they react and release their OH–<\/sup> and H+<\/sup> ions. These two ions combine to form water. Now sodium and chloride ions combine among themselves and form the salt sodium chloride.
\nThose reactions in which one element takes the place of another element in a compound, are as displacement reactions. In general, a more reactive element displaces a less reactive element compound. The examples of some important displacement reactions are given
\n![\"CBSE](\"https:\/\/i1.wp.com\/www.ncert-solutions.com\/wp-content\/uploads\/2018\/10\/CBSE-Sample-Papers-for-Class-10-SCIENCE-Set-1-6.png?resize=671%2C78&ssl=1\") <\/p>\nAnswer 10.<\/strong>
\nThe opening and closing of stomata is regulated by the activity of the guard cells. Guard cells are 2 kidney shaped cells present on either side of the stomata. They contain chloroplast. The space between the two guard cells is called the stomatal pore. When water flows into the guard cells they swell up thereby opening the stomatal pore. When guard cells lose water they shrink and the stomatal pore closes. Stomata are present on the surface of the leaves. Generally plenty of gaseous exchange takes place through these pores for photosynthesis. As there is a tendency to lose a lot of water through these pores by transpiration, the plant tends to keep the pores closed when gaseous exchange does not take place.<\/p>\nOR<\/strong><\/p>\nLungs are elastic, spongy, moist sacs like structures. Gaseous exchange occurs between alveoli and the blood vessels surrounding alveoli. Alveoli are tiny sacs like structures present in lungs which increases the surface area for gaseous exchange and lungs contain about 300-500 million alveoli. They have very thin walls making the diffusion of gases more convenient. They are surrounded by numerous tiny blood capillaries which facilitates for efficient gaseous exchange. During inhalation the ribs moves outward and diaphragm moves downwards so the space inside the thoracic cavity increases letting more amount of oxygen to diffuse inside.<\/p>\n Answer 11.<\/strong><\/p>\n\n\n\n\u00a0 \u00a0S. No.<\/strong><\/td>\nGlands<\/strong><\/td>\nEnzymes<\/strong><\/td>\n<\/tr>\n\n| (i)<\/td>\n | Salivary glands<\/td>\n | Salivary amylase<\/td>\n<\/tr>\n | \n| (ii)<\/td>\n | Pancreas<\/td>\n | \n Pancreatic amylase<\/p>\n Trypsin<\/p>\n Lipase<\/p>\n<\/td>\n<\/tr>\n | \n| (iii)<\/td>\n | Gastric glands<\/td>\n | Pepsin<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n Answer 12.<\/strong>
\nGiven: R2<\/sub> = 3 \u2126, I2<\/sub> = 1 A
\nV2<\/sub> = I2<\/sub> \u00d7 R2<\/sub>=1 \u00d73=3V
\n![\"CBSE](\"https:\/\/i1.wp.com\/www.ncert-solutions.com\/wp-content\/uploads\/2018\/10\/CBSE-Sample-Papers-for-Class-10-SCIENCE-Set-1-7.png?resize=578%2C339&ssl=1\") <\/p>\nAnswer 13.<\/strong>
\nA series of compounds in which the same functional group substitutes for hydrogen in a carbon chain is called a homologous series. Carbon atoms have the ability to be linked together to form chains of varying lengths. In addition, hydrogen atoms or atoms on these carbon chains can be replaced by any of the functional groups like alcohol, ketone, aldehyde, carboxylic acid and so on. The presence of the functional group dictates the properties of the carbon compound regardless of the length of the carbon chain. If we consider CH3<\/sub>OH, C2<\/sub><\/span>H5<\/sub>OH, C3<\/sub><\/span>H7<\/sub><\/span>OH, C4<\/sub><\/span>H9<\/sub>OH, their chemical properties are similar as all of them contain the OH group. As the molecular mass increases in the homologous series we can see a gradation in physical properties. The melting and boiling points increase with increasing molecular mass. Solubility in a particular solvent also increases. Chemical properties remain the same as they are determined by the functional group.<\/p>\nOR<\/strong><\/p>\n![\"CBSE](\"https:\/\/i2.wp.com\/www.ncert-solutions.com\/wp-content\/uploads\/2018\/10\/CBSE-Sample-Papers-for-Class-10-SCIENCE-Set-1-8.png?resize=709%2C105&ssl=1\") <\/p>\n
Answer 14.<\/strong>
\n![\"CBSE](\"https:\/\/i2.wp.com\/www.ncert-solutions.com\/wp-content\/uploads\/2018\/10\/CBSE-Sample-Papers-for-Class-10-SCIENCE-Set-1-9.png?resize=367%2C308&ssl=1\") <\/p>\nAnswer 15.<\/strong><\/p>\n\n\n\nInherited traits<\/strong><\/td>\nInherited traits<\/strong><\/td>\n<\/tr>\n\n(i)<\/strong> These are traits controlled by the DNA.<\/td>\n| These are traits not controlled by the DNA<\/td>\n<\/tr>\n | \n(ii)<\/strong> These traits are inherited.<\/td>\n| These traits cannot be inherited.<\/td>\n<\/tr>\n | \n(iii)<\/strong> These traits are not affected by the environment. Experience of the individual during its lifetime<\/td>\n| These traits are due to the environment or<\/td>\n<\/tr>\n | \n(iv)<\/strong> These traits can lead to variation which combined with genetic drift can lead to speciation.<\/td>\n| These traits do not lead to variation and do not play any major role in evolution.<\/td>\n<\/tr>\n | \n(v)<\/strong> Example: Attached or free earlobe and curly hair body.<\/td>\n| Example: Learning dance, music, muscular of a wrestler.<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n Answer 16.<\/strong>
\nSometimes we can see a random wavering or flickering of objects through a turbulent stream of hot air rising above a fire or a radiator. The air above the fire turns hotter than the air further up. The hotter air is lighter than the cooler air above it and the refractive index is also lesser than that of the cooler air. As the physical condition of the refracting medium (air) are not stationary, the apparent position of the object as seen through hot air fluctuates. This wavering is an effect of atmospheric refraction on a small scale in our local environment. The twinkling of stars is an effect of atmospheric refraction on a much larger scale. The starlight, on entering the earth’s atmosphere undergoes refraction continuously before reaching the earth.<\/p>\nSince the atmosphere bends starlight towards the normal, the apparent position of the star is slightly different from its actual position. The star appears higher than its actual position when viewed near the horizon. Moreover the position of the star keeps changing as the physical conditions of the earth’s atmosphere are not the same. As the stars are far away, the path of the light rays coming from them keeps varying slightly and the starlight entering the eye flickers. The star appears brighter at times and fainter at times, this produces the twinkling effect.<\/p>\n Answer 17.<\/strong>
\nSodium chloride is formed by the combination of sodium and chloride. Sodium has the electronic configuration 2,8,1. Chloride has the electronic configuration 2,8,7. When both of them combine, sodium tends to lose one electron to chloride and become \\({ Na }^{ + } \\) (sodium cation). Chloride picks up that electron and becomes \\({ Cl }^{ – } \\) (chloride anion). Now sodium (\\({ Na }^{ + } \\)) gets the stable configuration of 2, 8 and chloride (\\({ Cl }^{ – } \\)) gets the stable configuration 2,8,8. Sodium and chloride ions, being oppositely charged, attract each other and are held together by strong electrostatic forces of attraction to exist as sodium chloride (NaCl). As the compound sodium chloride is formed by the combination of sodium and chloride ions, the oppositely charged ions.
\n![\"CBSE](\"https:\/\/i1.wp.com\/www.ncert-solutions.com\/wp-content\/uploads\/2018\/10\/CBSE-Sample-Papers-for-Class-10-SCIENCE-Set-1-10.png?resize=329%2C205&ssl=1\") <\/p>\n | | | | | | | | | | | | | ![\"CBSE](\"https:\/\/i2.wp.com\/www.ncert-solutions.com\/wp-content\/uploads\/2018\/10\/CBSE-Sample-Papers-for-Class-10-SCIENCE-Set-1-1.png?resize=351%2C196&ssl=1\")
<\/p>\n![\"CBSE](\"https:\/\/i2.wp.com\/www.ncert-solutions.com\/wp-content\/uploads\/2018\/10\/CBSE-Sample-Papers-for-Class-10-SCIENCE-Set-1-2.png?resize=590%2C161&ssl=1\")