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St. Francis Xavier School Rehearsal Examination(2018-19) Subject Physics Class X Time 2hrs F.M. 80 Answer of this paper must be written on the paper provided separately. You will NOT be allowed to write during the first 15 minutes. This time is to be spent in reading the question paper. The time given at the head of this paper is the time allowed for writing the answers. Section I is compulsory. Attempt any four questions from Section II. The intended marks for questions or parts of questions are given in brackets [ ] Section I (40 MARKS) (Attempt all questions) Question 1: [2 x 5 = 10] a) A body of mass 1kg falls from a height of 5m. How much energy does it posses at any moment?( g =9.8m/s2) b) What is the effect of pressure on the boiling point of a liquid? c) A water pump can raise 20kg of water through a height of 10 m in 10 s. What is the total work done by the pump?[g=10m/s2] d) What are damped vibrations? e) What are naturally radioactive elements? Question 2: [2 x 5 = 10] a) 8000J of heat is given to 200g of copper at 20 C. What is the final temperature if the specific heat capacity of copper is 0.4J/g C? b) Two resistances of 3ohms and 2 ohms are connected across a 1.5 volt battery. Calculate the current in the main circuit, when the resistances are (i) in series, (ii) in parallel. c) What is an electric switch? What are its types? Describe a two way staircase switch. d) Draw a diagram of a step up transformer. e) Describe briefly the structure of an atomic nucleus. Give one example. Question 3: [2 x 5 = 10] a) Why water is not used in car radiators? b) The speed of light is 3 x 108 m/s. Calculate the frequency of yellow light of wavelength 6 x 10-7 m. 1 c) Differentiate between light and sound waves. d) A slab of ice at -6 C is constantly heated till it changes to steam at 110 C. Draw a graph showing the change of temperature with time. Label the different parts of the graph. e) An electric kettle is marked 220V, 1kW. What is the resistance of its heating element and the maximum current that can be safely carried by the elements? Question 4: [2 x 5 = 10] a) Explain the movement of electrons in a metal wire when potential difference is not applied and when it is applied across the ends. b) Draw a diagram to show the magnetic field of a current carrying solenoid. Which other source produces a similar field? c) State the principal of an AC generator. d) What happens to the volume of ice and lead when it melts? e) Name two radioactive elements other than uranium. Section II (40 MARKS) (Attempt any 4 questions) Question 5: a) Explain how a vibrating tuning fork produces sound waves in the air. Describe the nature of these waves. [3] b) A wave of frequency 500Hz travels between points P and Q with a velocity of 300 m/s. How many wavelengths are there in PQ if the length of PQ is 600m? [4] c) The velocity of sound wave produced by a string is 10m/s. From the diagram: i) find the wavelength. ii) find the amplitude of the wave. iii) calculate the frequency of the wave. 2 [3] Question 6: a) Steam at 100 C is passed over 1000g of ice at 0 C. After sometime 600g of ice at 0 C is left and 450g of water at 0 C is formed. Calculate the specific latent heat of vaporization of steam (given specific heat capacity of water = 4200J/kg C and specific heat of fusion of ice = 336,000 J/kg) [6] b) Describe the method of mixture for finding the latent heat of fusion of ice. [4] Question 7: a) There are four bulbs of voltage 25 W, 40 W, 60 W and 100 W. Which bulb will shine most brightly and why, when the bulbs are put in (i) series (ii) parallel with 200V source of AC? [4] b) (i) Why is tungsten used in an electric bulb? (ii) What is the purpose of argon inside the bulb? (iii) Why is the tungsten filament coiled? (iv) Write out the difference between the radiation emitted from a tungsten filament nichrome filament. Which is hotter? and a [4] c) Give two main precautions which you would take while putting off an electric switch. [2] Question 8: a) Why is a calorimeter made of a thin sheet of copper? [4] b) [4] (i) What is the advantage of laminated core in a transformer? (ii) What is the function of split rings in DC motor? c) Differentiate between a Class I and Class III lever. [2] Question 9: a) Explain how you will find the centre of gravity of an irregular lamina. [4] b) Draw a neat labeled diagram of a D.C. motor. Write any two uses of a D.C. motor. [6] Question 10: a) What is meant by the term (i) emf of a cell, (ii) internal resistance of a cell. The two ends of a coil of resistance 2.5 ohms are joined to the terminals of a Leclanche cell of emf 1.5 V. A current of 0.5 A flows in the circuit. What is the internal resistance of a cell? [4] b) State any two ways in which a liquid changes to vapour. Differentiate between these two ways. [4] c) If in nuclear fission of uranium, 2 g of mass is lost; how much energy in kWh is obtained? (This paper consists of 3 printed pages) 3 [2]
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