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ICSE Prelims 2015 : (Bishop Cotton Boys School (BCBS), Bangalore)

5 pages, 66 questions, 48 questions with responses, 54 total responses,

Karthik Suresh
Bishop Cotton Boys' School (BCBS), Bangalore

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BISHOP COTTON BOYS SCHOOL: BANGALORE TRIAL EXAMINATION : JANUARY 2015 PHYSICS STD. X DATE: 10.01.2015 MARKS: 80 TIME : 2 Hrs. Candidates are allowed additional 15 minutes for only reading the paper. They must NOT start writing during this time. The time given at the head of this paper is the time allowed for writing the answers. The intended marks for questions are given in brackets [ ]. This paper contains 5 printed pages. SECTION A [4 x10 = 40] Answer all questions Question I. a. State the energy changes that take place in the following when they are in use: i. a photovoltaic cell. ii. an electromagnet. [2] b. i. Name the class of levers has a mechanical advantage always greater than one? ii. What change can be brought about in this lever to increase its mechanical advantage? [2] c. Name the physical quantity that is measured in i. electron volt ii. kilowatt hour. [2] d. State two uses of a gear system. [2] e. i. How is force related to the momentum of a body? ii. State the condition when the change in momentum of a body depends only on the change in its velocity. [2] Question 2 a. i. A half metre ruler is suspended by a thread from the midpoint of the ruler as shown in figure 2. Fig - 1 Std.12/ 2014 2015 /Trial Exam /Physics /1 b. c. d. e. It balances horizontally when a 50g and an unknown weight w are suspended from 10cm and the 45cm mark. Calculate the magnitude of weight w . [2] Write the name of the force which provides the required centrepetal force in the following cases. i. A stone tied to one end of the string and whirled in a circular path. ii. Moon revolving round the earth in circular path. [2] i. In a single movable pulley ,if the effort moves by a distance x upwards, by what height is the load raised? ii. Obtain the relation between mechanical advantage and velocity ratio in the case of an ideal machine. [2] i. What is the name given to a cylindrical coil whose diameter is less in comparison to its length? ii. If a piece of soft iron is placed inside the current carrying coil, what is the name given to the device? [2] i. Why does a magnetic needle show a deflection when brought close to a current carrying conductor ? ii. A wire bent into a circle carries current in an anticlockwise direction . What polarity does this face of the coil exhibit? [2] Question 3 a. Calculate the equivalent resistance in the following network. [2] Fig - 2 b. c. d. e. State two properties of the material of the fuse wire which make it suitable for use. [2] Materials X and Y are solids that are at their melting temperatures, material X requires 200 J to melt 4 kg material Y requires and 300 J to melt 5 kg. Rank the materials according to their heats of fusion, in the descending order. [2] i. State the principle of calorimetry. ii. Give any two effects of greenhouse effect. [2] i. A radiation X is focused by a proper device on the bulb of a thermometer. Mercury in the thermometer shows a rapid increase. Name the radiation. Give any one use of it. [2] Std.12/ 2014 2015 /Trial Exam /Physics /2 Question 4 a. Which characteristic of sound will change if there is a change in i. amplitude ii. its waveform. b. c. d. e. [2] PQ and PR are two light rays emerging from the object P as shown in the figure below: Fig - 3 i. What is the special name given to the angle of incidence of ray PQ? ii. Copy the ray diagram and complete it to show the position of the image of the object P when seen obliquely from above. [2] Draw a graph showing the relationship between acceleration and force for a body of constant mass (m). [2] Draw the diagram of a transformer to be used to supply power to consumers from 11kV to 220 V. [2] A certain nucleus X has a mass number 14 and atomic number 6, this nucleus X changes to 7Y14 after the loss of a particle. i. Name the particle emitted. ii. Represent this change in the form of an equation. [2] SECTION B [4x10=40] Answer ANY FOUR from this section Question 5 a. i. Draw a labeled diagram of a simple d.c motor. ii. b. What determines the frequency of a.c produced in a generator? [4] The diagram shown in fig 4 is a coil connected to a centre zero galvanometer G. The galvanometer shows a deflection to the right when the North pole (N) of a powerful magnet is moved to the right. Fig 4 Std.12/ 2014 2015 /Trial Exam /Physics /3 i. ii. c. Explain why does the deflection occur in the galvanometer. State whether the current in the coil is clockwise or anticlockwise when viewed from the end P. iii. State the observation in the galvanometer G when both the coil and the magnet are moved to the right at the same speed. [3] A bulb rated 12 V, 24 W operates on a 12 V battery for 20 minutes. Calculate: i. the current flowing through it ii. the energy consumed. [3] Question 6 a. i. ii. iii. iv. b. c. Name a metal that is used as an electron emitter. Give one reason for using this metal. Name radiation which produces maximum biological damage? Write any one property of the radiation you have mentioned in question(iii). [4] 234 i. A nucleus 90 Th suffers several disintegrations ultimately to decay to 206 .Find the number of alpha and beta particles emitted. 82 Pb ii. Why do we use isotopes emitting gamma radiations as radioactive tracers in medical science? [3] Calculate the heat capacity of a copper vessel of mass 150 g if the specific heat capacity of copper is 410 J / kg K. How much heat energy will be required to increase its temperature from 25 C to 35 C. [3] Question 7 a. i. Which of the following remains constant in uniform circular motion : speed or velocity or both? ii. Name the force required for a body to perform uniform circular motion. iii. A crowbar of length 1.2 m has its fulcrum at a distance of 0.2 m from load. Calculate the Mechanical Advantage ( MA) of crowbar. [4] b. Draw a ray diagram to show how a converging lens is used as a magnifying glass to observe a small object. [3] c. i. A ray of light is incident normally on a plane glass slab. What will be the angle of refraction for this ray? ii. Define the term refractive index of a medium. What do you understand by the statement the refractive index of glass is 1.5 for white light ? [3] Question 8 a. With reference to electrical wires write the international colour code for the three wires ? [1] Std.12/ 2014 2015 /Trial Exam /Physics /4 b. c. d. e. Calculate the reading of ammeter when i) Key (K) is closed when ii) Key (K) is open. Fig 5 [3] Name a device which is commonly used to convert an electrical signal into a visual signal. [1] State Ohm s law. [1] A refrigerator converts 100g of water at 20 C into ice at -10 C in one hour. Determine the quantity of heat extracted per second. Latent heat of fusion of ice = 336J/g, Specific heat capacity of ice = 2.1 J/g C, Specific heat capacity of water= 4.2 J/g C. [4] Question 9 a. Define work function metal. State any one important factor which affects the rate of thermionic emission [2] b. i. Write an expression for the electrical energy spent in the flow of current through an electrical appliance in terms of I, R, t. (all symbols have their usual meaning) ii. At what voltage is the alternating current supplied to our houses? iii. How should the electric lamps in a building be connected? (series or parallel) [3] c. Write the necessary condition for hearing an echo. [2] d. A radar sends a signal to an aero plane at a distance 45 km away with a speed of 3x 108 m/s. After how long is the signal received back from the aero plane? [3] Question 10 a. Why are the racing cars very broad and very low? [2] b. Name the device used for measuring i) mass ii) weight. [2] c. A body is acted upon by a force. State two conditions under which the work done could be zero. [2] d. Draw a diagram of block and tackle system of pulleys having a velocity ratio of 5 .In your diagram clearly indicate the points of application and the directions of the load and effort. Also mark the tension in each strand. [4] Std.12/ 2014 2015 /Trial Exam /Physics /5

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