Paper : ICSE Class X Important Questions : Physics (2005)

Question 1

(a) Which physical quantity does the electron volt measure? How is it related to the S.I. unit of this quantity? [2]

(b) What should the angle between force and displacement be to get the

1. minimum work;
2. maximum work?

(c) State Newton's second law of motion. [2]

(d) The work done by the heart is 1 Joule per beat. Calculate the power of the heart if it beats 72 times in one minute.[2]

(e) Mention two properties of a wave: one property which varies and the other which remains constant when the wave passes from one medium to another.[2]

Question 2

(a) Explain briefly what causes the twinkling of stars at night. [2]

(b) State two advantages of an aneroid barometer. [2]

(c) Explain why a gas bubble released at the bottom of a lake grows in size as it rises to the surface of the lake. [2]

(d) What is meant by the statement, 'the critical angle of diamond is 24⁰ '? How is the critical angle of a material related to its refractive index? [2]

(e) A block of wood of volume 25cm³ floats in water with 20cm³ of its volume immersed. Calculate:

1. the density and
2. the weight of the block of wood.

Question 3

(a) Name any two electromagnetic waves which have a frequency higher than that of violet light. State one use of each. [2]

(b) State two ways by which the frequency of transverse vibrations of a stretched string can be decreased. [2]

(c) Why does the temperature of the surroundings start falling when the ice of a frozen lake starts melting? [2]

(d) Four resistances of 2.0Ω each are joined end to end to form a square ABCD. Calculate the equivalent resistance of the combination between any two adjacent corners. [2]

(e) In a three-pin plug, why is the earth pin made longer and thicker than the other two pins? [2]

Question 4

(a) State the energy change which takes place when a magnet is moved inside a coil having a galvanometer at its ends. Name this phenomenon. [2]

(b) Draw a labelled diagram of an A.C. generator. [2]

(c) Calculate the heat energy that will be released when 5.0 kg of steam at l00⁰ C condenses to form water at 100⁰C. Express your answer in S.I. unit. (Specific latent heat of vaporization of steam is 2268 KJ /Kg.) [2]

(d) How many alpha and beta particles are emitted when Uranium nucleus ²³⁸₉₂ U decays to Lead ²⁰⁶₈₂? Pb[2]

(e) With the help of an equation, state the mechanism of energy production in a nuclear fusion reaction. [2]

SECTION II (40 Marks)
Attempt any four questions from this Section.

Question 5 [3]

(a) (i) State the law of conservation of energy.

(ii) Name the chief energy transformation that occurs

1. in a Loudspeaker;
2. in an Electrical cell (Primary).

(b) (i) Define an Inclined plane.

(ii) Draw a labelled sketch of a class II lever. Give one example of such a lever. [3]

(c) The alongside figure shows the combination of a movable pulley. P_I with a fixed pulley P_{2 used for lifting up a load W. [4]}

1. _{State the function of the fixed pulley P2.}
2. _{If the free end of the string moves through a distance C, find the distance by which the load W is raised.}
3. _{Calculate the force to be applied at C to just raise the load W = 20 kgf, neglecting the weight of the pulley P1 and friction.}

_{Question 6}

_{(a) Water falls from a height of 50 m. Calculate the rise in the temperature of water when it strikes the bottom.
(g = l0 ms^-2 Specific heat capacity of water = 4200 J/kg⁰C) [3]}

_{(b) Draw a labelled diagram of a common hydrometer and state the principle used in its working. [3]}

_{(c) A solid body weighs 2.10 N in air. Its relative density is 8.4. How much will the body weigh if placed: [4]}

1. _{in water;}
2. _{in a liquid of relative density 1.2?}

_{Question 7 [3]}

_{(a) The ray diagram given below illustrates the experimental set up for the determination of the focal length of a converging lens using a plane mirror.}

1. _{State the magnification of the image formed.}
2. _{Write two characteristics of the image formed.}
3. _{What is the name given to the distance between the object and optical centre of the lens in the diagram?}

_{(b) (i) A glass slab is placed over a page on which the word VIBGYOR is printed with each letter in its corresponding colour.}

1. _{Will the image of all the letters be in the same place?}
2. _{If not, state which letter will be raised to the maximum. Give a reason for your answer.}

_{(ii) What will be the colour of an object which appears green in white light and black in red light?}

_{(c) (i) What is meant by refraction?}

_{(ii) Express the refractive index n of a medium:
(1) in terms of the velocity of light;}

_{(2) in terms of the angle of incidence i in air and the angle of refraction r in a denser medium.}

_{(iii) If a ray of light passes from medium I to medium II without any change of direction, what can be said about the refractive indices of these media (angle i is not 0)?}

_{Question 8 [3]}

_{(a) A radar is able to detect the reflected waves from an enemy aeroplane, after a time interval of 0.02 milliseconds. If the velocity of the waves is 3 × 108 ms^-1, calculate the distance of the plane from the radar. [3]}

_{(b) A piece of ice is heated at a constant rate. The variation of temperature with heat input is shown in the graph below:}

1. _{What are represented by AB and CD ?}
2. _{What conclusion can you draw regarding the nature of ice from the alongside graph?}

_{(c) If there is no heat loss to the surroundings, the heat released by the condensation of m2g of ice at, 0⁰C into water at 0⁰C. [4]}

_{(i) Find:}

1. _{the heat lost by steam in terms of m1}
2. _{the heat gained by ice in terms of m2.}

_{(ii) Form a heat equation and find the ratio of m2 : m1 from it.}

_{(Specific latent heat of vaporization of steam = 2268 kJ/kg;
Specific latent heat of fusion of ice = 336 kJ/kg.
Specific heat capacity of water = 4200 J/kg⁰C).}

_{Question 9 [3]}

_{(a) An electrical appliance is rated 1500 W, 250 V. This appliance is connected to 250 V mains. Calculate:}

1. _{the current drawn,}
2. _{the electrical energy consumed in 60 hours,}
3. _{the cost of electrical energy consumed at Rs. 2.50 per KWH.}

_{(b) (i) State the function of a split ring in a D.C. motor. [4]}

_{(ii) Mention two reasons why a soft iron core is used within the coil of a moving coil galvanometer.}

_{(c) In the figure given alongside, A, B and C are three ammeters. The ammeter B reads 0.5A. (All the ammeters have negligible resistance.) [4]}

_Calculate:

1. _{the readings in the ammeters A and C.}
2. _{the total resistance of the circuit.}

_{Question 10 [3]}

_{(a) State the functions of the following in a nuclear reactor:-}

1. _Moderator,
2. _{Control rods,}
3. _Coolant.

_{(b) (i) Mention two important precautions that should be taken while handling radioactive materials. [3]}

_{(ii) State one use of radioisotopes.}

_{(c) (i) Draw a labelled diagram of a hot cathode ray tube. [4]}

_{(ii) Why are materials of low work function preferred as thermionic cathode materials?}

_{(iii) Write an equation to show the fission of a nucleus of U²³⁵ with the production of three neutrons.}