SCIENCE JULY 2016 PAPER ONE
Q. I. (A) ANSWER THE FOLLOWING SUB - QUESTIONS:
(1) Fill in the blanks and rewrite the completed statements: [2]
(a) To increase the effective resistance in a circuit, the resistors are connected in _______________ (Series)
(b) The phenomenon of splitting of light into its component colours is ___________ (dispersion)
(2) State whether the following statements are true or false: [2]
(a) Phenolphthalein is a synthetic type of indicator. [True]
(b) The chemical reactions in which heat is liberated are called endothermic reactions. [False]
(3) Name the following: [1]
The instrument used to observe planets.
Ans. The instrument used to observe planets is telescope.
(B) Rewrite the following statemnts by selecting the correct options. [5]
(1) When the resistance of a conductor increases, the current ____________
(a) increases
(b) decreases
(c) remains the same
(d) increaes or decreases
(2) The phenomenon of change in the direction of light when it passes from one transparent medium to another is called ___________
(a) dispersion
(b) scattering
(c) Refraction
(d) Reflection
(3) When _______________ is passed through fresh lime water, it turns milky.
(a) H2
(b) CO2
(c) CO
(d) SO2
(4) A _____________ mirror is used by a dentist.
(a) concave
(b) convex
(c) plane
(d) none of the above.
(5) The equivalent resistance of a parallel combination of two resistors of 30 Ω and 60 Ω is ______________
(a) 90 Ω
(b) 2 Ω
(c) 20 Ω
(d) 1800 Ω
Q. II. Attempt any five of the following: [10]
(1) The velocity of light in a medum is 1.5 x 188 m/s. What is the refractive index of the medium with respect to air, if the velocity in the air is 3 x 108 m/s ?
Ans. Given data: V1 = 3 x 108 m/s; V2 = 1.5 x 108 m/s ; 1η2 = ?
Solution: We know that,
1η2 = V1 / V2
ஃ 1η2 = (3 x 108) / (1.5 x 188)
ஃ 1η2 = 2
Ans. The refractive index of the medium with respect to air is 2.
(2) Give Scientific Reasons:
Grills of doors and windows are always painted before they are used.
(3) Write a short note on Eutrophication.
(4) Classify the given elements into metals, non - metals and metalloids. :
Carbon, Boron, Sodium, Oxygen.
Ans. Carbon in a non metal.
Boron is a metalloid.
Sodium is a metal.
Oxygen is a non - metal.
(5) State Fleming’s Right Hand Rule.
(6) Distinguish between oxidation and reduction.
Oxidation
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Reduction
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The chemical reaction in which reactants rain oxygen atoms to form corresponding oxides are known as oxidation reactions.
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The chemical reactions in which reactanta gain hydrogen are called reduction reactions.
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The chemical reactions in which reactants lose hydrogen atoms to form products are called as oxidation reductions.
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The reactions in which reactants lose oxygen atoms to form products are called as reducation reactions.
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Q. III. Attempt any five of the following: [15]
(1) Aniket from Std. X uses spectacles. The power of the lenses in his spectacles is - 0.5 dioptre.
Answer the following questions:
(a) Concave type of lenses are used in Aniket’s Spectacles.
Reason: Concave since power of the lens is negative.
(b) Name the defect of vision Aniket is suffering from.
Ans. Aniket suffers from an eye defect known as myopia.
(c) Find the focal length of the lenses used in his spectacles.
Answer: Power of lens in dioptre = 1 / focal length in metres.
Therefore, - 0.5 = 1 / f(m)
Therefore, f(m) = 1 / - 0.5
Therefore, f(m) = 2 m.
Therefore, the focal length of the lenses used in Aniket’s spectacles is - 2 m.
(2) What are the demerits of Mendeleev’s periodic table?
(3) Explain how the formation of the rainbow occurs.
(4) State the different positions of the source of light with respect to the concave mirror in:
(a) torches (b) projector lamps (c) flood lights
Ans. (a) torches : The source of light i.e. bulb is placed at the focus of the concave morror.
(b) projector lamps: The source of light i.e. bulb is placed just beyond the centre of curvature.
(c) flood lights: The source of light i.e. bulb is placed just beyond the centre of curvature.
(5) What major harms are done to human beings due to air pollution?
(6) Explain: pH scale with proper diagram.
Q. IV. Attempt any one of the following: [5]
(1) When do you say that the resistors are connected in this way. Draw a circuit diagram.
(2) Explain the construction and working of an electric generator (AC) with the help of a neat diagram.
