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Section A [2*5*4=40] Question 1 (a) i. What are non contact forces? Name the non-contact force which is always attractive. ii. Name the principle on which beam balance works. (b) i. What is meant by centre of gravity of a body? ii. Where is the centre of gravity of a hollow cone located? (c) i. Give two examples of energy degradation from daily life. ii. What is the work done by a satellite revolving around Earth in a circular orbit? Why? (d) i. Give two reasons why the efficiency of a simple machine is not 100% ii. Name the single pulley which has no gain in mechanical advantage. (e) Name the class of lever-i. Wheel barrow ii. Fishing rod iii. Stapler iv. Crowbar Question 2 (a) Why a closed soft iron laminated core is used in a transformer? (b) A combination of 6 ohm and 12 ohm resistors connected in parallel, is connected in series with a 12 ohm resistor and a 3 ohm resistor. This combination is connected in series with a cell of e.m.f. 5V of internal resistance. Draw a diagram of the arrangement and calculate the current in the circuit. (c) i. Draw a labeled diagram of a three-pin socket. ii. Name the material used to make heating element and give reasons for your choice (d) Distinguish e.m.f. and terminal voltage of a cell (e) i. State the Principle of Calorimetry ii. What is it also known as? Question 3 (a) A good thermion emitter has a -------------- work function and -------------- melting point (b) i. A radioactive substance is converted to another compound in a chemical reaction. What change is expected in its radioactivity? Why? ii. Name the radiation which is most deflected in an electric field. (c) As winter starts, people in cold countries gather around a pond which has started freezing. Why? (d) Calculate the power of a heater which converts a mixture of 20 g of ice at 0 C and an additional 50 g of ice at -20 C to water at 50 C in 48 s. (e) State the subjective property of: i. Light related to its wavelength ii. Sound related to its frequency Question 4 (a) A pulley system has velocity ratio equal to 5 and an effort of 200 N is required to lift a load of 750 N. Calculate its efficiency. If load moves up by a distance 5 m by what distance will the effort move? (b) State two technological measures to minimize the impact of global warming (c) 92U235 undergoes nuclear disintegrations to ultimately form 82Pb207. Calculate the minimum number of alpha and beta particles emitted. (d) Calculate the frequency of an electromagnetic wave of wavelength 500 nm. Name the part of the spectrum to which it belongs. (e) A lens is placed in water. What change is expected in its focal length? Why? Section B Question 5 (a) A fire tongs has a length of 48 cm and effort of 80 N is applied at a distance of 12 cm from its fulcrum to lift a load of 16 N. i. Calculate its mechanical advantage, velocity ratio and efficiency. ii. Name another lever of the same class as fire tongs. iii. State the utility of the class of levers to which both belong. [3] (b) i. Name the forces acting on a body placed on an inclined plane. ii. How does a car driver use gear system while ascending up a hill? iii. Why is it easier to open a bottle with all fingers than one finger? [3] (c) i. Two boys of masses 50 kg and 60 kg respectively are sitting on the opposite sides of a see-saw at distances 1 m and 2 m respectively from centre. Where should a man of mass 85 kg sit to balance the see-saw? ii. A man of mass 60 kg climbs up 25 stairs each 20 cm high and then another 20 stairs each 30 cm high in 1 minute. Another man does the same in 90 seconds. Calculate the work done by each and compare the power developed by them. [4] Question 6 (a) i. State two differences between free and forced vibrations. ii. Name the phenomenon involved in tuning a radio set to a particular station. [3] (b) i. We get to know the filling of water in a pan from a distance due to a change in the sound produced. What is the change in sound and what is the cause for the same. ii. Name and define the most common unit of sound level. [3] (c) i. Why are ultrasonic waves used for applications of echo? ii. Compare the velocities of ultrasound and infrasound. iii. A source produces 25 transverse vibrations per second and the pulse travels through the medium with a velocity of 600 m/s. Calculate the distance between a crest and a trough and also the time period of pulse. [4] Question 7 (a) Name the kind of electromagnetic radiationsi. Produced in Coolidge tubes ii. Used in satellite communication iii. Used in remote signal control [3] (b) A certain type of lens is used for correcting chromatic aberration caused by convex lens. i. Name the type of lens and state its action on light rays incident on it. ii. Draw a ray diagram to show formation of image when light rays parallel to principal axis are incident on it. Give one application for the same. [3] (c) i. Complete the following diagram till the ray emerges out of the prism. ii. Name the phenomenon involved and the conditions for the occurrence of the same. [4] Question 8 (a) i. State the characteristics of a high tension wire. ii. How should appliances in a building be connected? iii. State the new colour coding for live and neutral wires. [3] (b) i. A wire is quadrupled on itself. What change is expected in its resistivity? ii. Name and state the law which expresses the relation between potential difference and current at constant temperature. [3] iii. State one way of increasing speed of rotation of a direct current motor. (c) i. State the polarity at A. ii. Name two rules which can be used to determine polarity of a solenoid. iii. Name and define the principle on which a transformer works. [4] Question 9 (a) i. Radioactivity is a random phenomenon. What does this mean? ii. Name the radiations (i) Has highest ionizing power (ii) Travels with a velocity equal to 90% of speed of light [3] (b) i. Why is cathode ray tube between electron gun and fluorescent screen graphite-coated and the tube earthed? ii. Why tungsten, though having high melting point, not used as an electron emitter as such? What is it coated with and for what? [3] (c) i. When is the deflecting couple maximum in a d.c. motor? ii. Why is alternating current preferred over direct current in household purposes? iii. How is an electromagnet more advantageous than a permanent one? iv. Name and state the law which forms the basis of Lenz s law and principle of mixtures. [4] Question 10 (a) i. State the change in volume of water on freezing and boiling. ii. Why bases of cooking pans are made thick and heavy? [3] (b) i. What is meant by global warming? ii. State two economic measures to abate global warming. [3] (c) i. There are two liquids A and B. A has specific heat capacity 360 J/g/K and b has specific heat capacity 4000 J/g/K. Which one is the better conductor of heat and which one is useful for fomentation? ii. How much ice remains unmelted if 300 g of copper chips at 500 C and 800 g of iron pieces at 300 C are mixed with 600 g of ice? Specific latent heat of fusion of ice=336 J/g, Specific heat capacities of copper and iron=400 J/kg/K, 450 J/kg/K [4]
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