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SECOND PRELIM EXAMINATION 2015-16 STD: 10 Date: 16/1/16 Marks: 80 Dur: 2 hrs. Subject: Physics SECTION I (40 Marks) (All questions in this section are compulsory) Question 1:(a) A unit of a physical quantity is stated as kgm2s-2. Name and define the physical quantity. 2 (b) A train is travelling on level track at a speed of 72 km/h. It is pulled by an engine which exerts a force of 12000 N. Calculate the power of the engine in kilowatt. 2 (c) What are contact forces? Give an example. 2 (d) The hammer of an electric bell strikes 1440 times in a minute and does a work of 0.2 J per strike. What is the power of hammer in SI system? 2 (e) Sate two differences between a mechanical wave and electromagnetic wave. 2 Question 2 :(a) Explain why the bottom of the tank filled with water appears raised. (b) The handle of water pump 80 cm long has fulcrum at a distance of 15 cm from the load. If a load of 80 N is overcome, calculate the effort applied. (c) Why is the mechanical advantage of class 3 lever always less than 1. (d) When does a ray of light passing through a rectangular glass slab does not suffer refraction? What is the angle of incidence in such a situation? (e) Name a material whose resistance:i) Increases with rise in temperature ii) Remains unaffected with the rise in temperature. Question 3:(a) Complete the ray diagram below,( ic = 42 ) 2 2 2 2 2 2 45 87 (b) A wire of length 120 cm and area of cross section 0.2 cm 2 offers a resistance of 4 . Calculate the specific resistance of the wire. (c) Define the commercial unit of electrical energy. Express the unit in the S.I unit. (d) A bulb of resistance 400 glows brightly when connected to line voltage V. If the power of bulb is 100 W, calculate the value of V. (e) Calculate the heat energy required to convert 5 g of ice at 0 0 C to water at 00 C. (Specific latent heat of ice is 336 Jg-1, specific heat capacity of water is 4.2 Jkg-1 0C-1) Page 1 of 3 2 2 2 2 Question 4 :(a) Which of the two cable wires, one of 10A and other of 20A will be thicker? Give one reason for your answer. (b) Give any two advantage of using a Ring system in a house. (c) Why is the primary coil of a step-up transformer made thick as compared to secondary coil? (d) What are radio-isotopes? State one use of radio-isotopes. (e) Name the two wires of household wiring circuit which are at the same potential 2 2 2 2 2 SECTION II ( 40 marks ) [ Answer any four questions from this section ] Question 5 :(a) 6.4 kJ of energy cause a displacement of 64 m in a body in the direction of force in 2.5 seconds. Calculate the force applied and the power (in HP) Take 1 HP = 746 W. 3 (b) A pulley system comprises of two pulleys, one fixed and the other movable. 3 i) Draw a labeled diagram of the arrangement and show clearly the directions of all the forces acting on it. ii) What change can be made in the movable pulley of this system to increase the mechanical advantage of the system? (c) Show that for the free fall of a body, the sum of the mechanical energy at any point in its path is constant. 4 Question 6:(a) Draw a simplified labeled diagram of a hot cathode ray tube. Name a common device where it is used. 3 (b) i) Write an expression for the heat energy liberated by a hot body. ii) Some heat is provided to a hot body to raise its temperature by 25 0 C. What will be the corresponding rise in temperature of the body as shown on the Kelvin scale? iii) Write down a relationship between Thermal capacity and Specific heat capacity 3 0 (c) 40 g of ice at 0 C is used to bring down the temperature of a certain mass of water at 600C to 100c. Find the mass of water used. 4 [Specific heat capacity of water = 4200 Jkg -1 0C-1] [Specific latent heat of fusion of ice = 336000 Jkg -1] Question 7:(a) Draw a ray diagram to illustrate the formation of an enlarged and upright image of an object by a lens.Name the device where this action of lens is used. (b) Define Critical angle. State two conditions for total internal reflection. (c) i) Name any four regions of electromagnetic spectrum in increasing order of frequency. ii) Calculate the refractive index of a liquid with respect to air using Snell s law 300 3 3 2 2 Air Liquid 450 Question 8:(a) What is meant by Resonance. State two ways in which Resonance differs from Forced vibrations. 3 (b) A man standing between two cliffs produces a sound and hears two successive echoes Page 2 of 3 at intervals of 3 sec and 4 sec respectively. Calculate the distance between the two cliffs. (The speed of sound in air is 330 ms-1) Why will an echo not be heard when the distance between the source of sound and the reflecting surface is 10 m. 3 (c) i) What is meant by the term Amplitude of a wave and Frequency of a wave. 2 ii) Explain why stringed musical instruments, like the guitar are provided with a hollow 2 box. Question 9:(a) i) State Ohm s law. ii)The V-I graph for series and parallel combination of two resistors is shown in the figure given below. Which of the two A or B represents the parallel combination? Give reason for your answer. V B 3 A I (b) What is the principle of Calorimetry. State the effect of increase of impurities on melting point of ice and boiling point of water. 3 c) ) Mention two methods to reduce global warming. 2 ii) Why is the earth pin, in a three-pin plug, longer and thicker than the other two pins? 2 Question 10:(a) i) What is thermionic emission? ii) Name the unit in which the work function of a metal is expressed. iii) State any two precautions to be taken while handling radioactive substances. 3 (b) An atomic nucleus A is composed of 84 protons and 128 neutrons. i) The nucleus A emits an alpha particle and is transferred into nucleus B. What is the composition of nucleus B? ii) The nucleus B emits a beta particle and is transformed into a nucleus C. What is the composition of nucleus C? iii) Does the composition of nucleus C change if it emits gamma radiations? 3 (c) Draw a diagram for the magnetic field in a circular coil, when the current in the coil flows in clockwise direction. 2 (d) In what position of coil (in degrees) the deflecting couple acting in D.C motor is: 2 i) maximum ii) minimum ________________________ Page 3 of 3
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