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# ISC Prelims 2016 : Physics (The Ashram, Chennai)

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 S Sudha The Ashram, Chennai
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PHYSICS SCIENCE Paper - 1 (Two hours) Answers o this Paper muss be written on the paper provided separately. You will not be allowed to write during 11w first 5 minutes. This time is to be spent in reading the Question Paper. The time given al the head of this Paper is the time allowed for writing the answers. Section is compulsory. Attempt any four questions from Section Ii The intended marks for questions or parts of questions are given in brackets (j. SECTION 1(40 Marks) Attempt ail questions from this Section. Question 1 (a) A force is applied on (1) a non-rigid body and (ii) a rigid body. How does the effect of the force differ in. the aboue two cases2 L2) (b) Where does the position of ce nl re of gravity tie for (i) a circular lamina (ii) a triangular lamina 121 (c) (j) On what factor does the position of the centre of gravity of a body

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depend? (ii) What is the S.1.unit of the moment of force? (2] . . - . . tJ (d) (t) What is meant by the term moment of force T (ft) If the moment of force is assigned a negative sign then will the turning tendency of the /brce be clockwise or anticlockwise? f 2J (e) A type of single pulley is very often used as a machine even though it does not give any gain in mechanical advantage. (j) Name the type of pulley used. (ii) For what purpose is such a pulley used? [2] Question 2 () (i) State the energy conversion taking place in a solar cell. (ii) Give one disadvantage of using a solar cell. [21 (b) n the diagram below, PQ is a ray of light incident on a rectangular glass block. (i) Copy the diagram and complete the path of the ray Q of light through the glass block. In your diagram, mark the angle of incidence by letter 1 and the

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angle of emergence by the letter C - ____ (ii) How are the angle j and e related to each other? [2] (C) (j) A scissor is a ________ multiplier. (ii) 1 kWh _______ J. [2] (d) State one important advantage and disadvantage each of using nuclear energy for producing electricity. [2] (e) (1) The refractive index of glass with respect to air is 1.5. What ia the value of the refractive index of air with respect to glass? (ii) A ray of light is incident as a normal ray on the surface of separation of two different mediums. What is the value of the angle of incidence in this case2 (2] Question 3 (a) (i) What is meant by Dispersion of light ? (ii) In the atmosphere which colour of light gets scattered the least? [21 (b) ( ) Three musical instruments give out notes at the frequencies listed below. Flute :400 Hz; Guitar :200 Hz; Trumpet :500 Hz. Which one of these has th. highest pitch? (ii) With which of th. following frequencies does a tuning fork of 256 Hz

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resonate 2288 Hz, 314 Hz, 333 Hz, 512 Hz. 121 (c) (I) Draw a graph between displacement and the time for a body executing free vibrations. (ii) Where can a body execute free vibrations? 12] (d) You have been provided with a solenoid AB. L, J (1) What is the polarity at end A 2 (ii) Giue one advantage of an electromagnet over a permanent ,ncixnet. 121 (e) (1) Name a prism required for obtaining a spectrum of Ultraugotet Light. (ii) Name the radiations which can be detected by a thermopile. [21 Ouestion 4 (a) Define the term Heat capacity and state its S.J. unit. L21 (b) (I) Define Calorimetry. (u) What is meant by Energy degradation? 121 (c) A hot solid of mass 60g cit 100C is placed in 150g of water at 20C. The final steady temperature recorded is 25C. Calculate the specific heat capacity of the solid. (Specific heat capacity of water = 4200 J kg .01) (2) () Give two similarities between an A.C. generator and a D.C. motor. [2)

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(e) An electron emitter must have work function and . melting point. [2J SECTION 11(40 Marks) Attempt any four questions from this Section Question 5. (a) Ci) Which of the following remarns constant in uniform circular motion: Speed or Velocity or both? (ii) Name the force required for uni form circular motion. State its direction. 131 (b) (i) State the class of levers and the relatiue positions of load (L), effort (E) and fukrum (F) in each of the following cases: 1. A bottle opener. 2. Sugar tongs. (ii) Why is less effort needed to lift a load over an inclined plane as compared to lifting the load directLy? 13) (c) (1) A moving body weighing 400 N possesses 500 J of kinetic energy. Calculate the velocity with which the body is moving. (g =10 ms2) (ii) Under what condition wilt a set of gears produce:

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1. a gain in speed. 2. a gain in torque. 14] Question 6 (a) Name the radiations: (i) That are used for photography at nighL (ii) Used for detection of fracture in bones. (iii) Whose wavelength range is from 100 A to 4000 A (or 10 nm to 400 nm). (31 (b) ( ) Can the absolute refractive index of a medium be less than one? (ii) A coin placed at the bottom ola beaker appears to be raised by 4.0 cm. If the refractive index of water is 4/3, find the depth of the water in the beaker. (3) (c) An object AB is placed between 2F1 and F3 on the principal axis of a convex lens as shown in the diagram: II F1 F2 2F2 Copy the diagram and using three rays starting from point A, obtain the image of the object formed by the Lens. [4]

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9estion 7 . (a) (I) State the safe limit of sound level in terms of decibel for human hearing. (ii) Name the characteristic of sound in relation to its avefonn. [2] (b) A person standing between two vertical cliffs and 480 m from the nearest cliff shouts. He hears the first echo after 3s and the second echo 2s later. Calculate: (i) The speed of sound. (ii) The distance of the other cliff from the person. [31 (e) In the diagram below, A, B, C, D are four pendulums suspended from the same elastic string PQ. The length of A and C are equal to each other while the length of pendulum B is smaller than that of D. Pendulum A is set into a mode of vibrations. P. ________ ? (I) Name the type of vibrations taking place in pendulums B and D? (ii) What is the state of pendulum C? (iii) State the reason for the type of vibrations in pendulums B and C. [5] Question 8.

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(a) Two resistors of 412 and 60 are connected in parallel to a cell to draw 0.5 A. current from the cell. (j) Draw a labelled circuit diagram showing the above arrangement. (ii) Calculate the current in each resistor. . 13] (b) (j) What is an Ohmic resistor? (ii) Th,o copper wires are of the same length, but one is thicker than the other. (1) Whkh wire will have mire resistance? (2) Which wire will have more specific resistance? [3] (c) (j) Two vets A and B, of the three bulbs each, are glowing in two separate rooms. When one of the bulbs in set A is fused, the other two bulbs also cease to glow. But in set B, when one bulb fi ses, the other two bulbs continue to glow. Explain why this phenomenon occurs. ( ) Why do we prefer arrangements of Set B for house circuiting? (3) -- Question 9. (a) (I) Explain why the weather becomes very cold after a hail storm. (ii) What happens to the heat supplied to a substance when the heat supplied causes no change in the temperature of the substance 131

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(b) (j) When 1g of ice at O C melts to form 1g of waler at O C then, is the latent heat absorbtd by the ice or given out by it t (ii) Give one example where high specific heal capacity of water is used as a heat reservoir. (iii) Cive one example where high specific heat capacity of water is used for cooling purposes. (3] (c) 250g of water at 30 C is present in a Capper vessel of mass 50g. Calculate the mass of ice required to bring down the temperature of the vessel and its contents toS C. Specific latent heal of fusion of ice = 336 r 101 J kg . Specific heat capacity of copper vessel 400 J kg- C . Specific heat capacity of water = 4200 J kg 0 . 14J Question 10 (a) (j) What is thermionic emission? (ii) Name the unit in which the work function of a metal is expressed. 121 Radioactive Substance

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4 Lead Box (b) ( ) Complete the diagram as given above by drawing the deflection of radioactive radiations in an electric field. (Ii) State any two precautions to be taken while handling radioactive substances. (e) An atomic nucleus A is composed of 84 protons and 128 neutrons. (I) The nucleus A emits an alpha particle and is transformed into nucleus B. What is the composition of nucleus B? (ii) The nucleus B emits a beta particle and is transformed into nucleus C. What is the composition of nucleus C? (iii) Does the composition of nucleus C change fit emits gamma radiations? [511 131