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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
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