Paper : ICSE Class X Important Questions : Physics (1999)

General Instructions

1. Attempt all questions from Section I and any four questions from Section II.
2. The intended marks for questions or parts of questions are given in brackets.

SECTION I (40 Marks)
Attempt all questions from this Section.

Question 1
(a)

1. Will the weight of an 'iron sinker plus cork' combination in water be more or less than that of the iron sinker alone in water? Give a very brief explanation for your answer. [1]
2. The mass of a body is 70 kg. When completely immersed in water, it displaces 2000 cm³ of water. What is the relative density of the material of the body? [3]

(b) (i) State two ways, other than direct heating by which a given quantity of liquid can be made to evaporate more quickly. [2]

(ii) The temperature recorded by a thermometer decreases when its bulb is covered with a piece of cloth soaked in spirit. Explain why? [2]

(c) (i) Draw a ray diagram to illustrate how a ray of light incident obliquely on one face of a rectangular glass slab of uniform thickness emerges parallel to its original direction. Mention which pairs of angles are equal? [2]

(ii) Is it possible to burn a piece of paper using a convex lens in daylight without using matches or any direct flame? Draw a diagram to support your answer. [2]

(d) Draw a ray diagram to show what happens to a parallel beam of light as it passes into a short-sighted or myopic eye. [4]

(ii) How can the beam be brought to focus on the retina? Illustrate your answer with an appropriate diagram. [2]

(e) The diagram below shows an object AB placed on the principal axis of a lens L. The two foci of the lens are F₁ and F₂. The image formed by the lens is erect, virtual and diminished. Copy the diagram and answer the following questions: [4]

1. Draw the outline of the lens (L) used.
2. Draw a ray of light starting from B and passing through O. Show the same ray after refraction by the lens.
3. Draw another ray from B, which after passing parallel to the principal axis, is incident on the lens and emerges after refraction from it.
4. Locate the final image formed.

(f) (i) Give the difference between spectral and pigment colours. [2]

(ii) A green shirt is observed in blue light. What colour will it appear to be and why? [2]

(g) (i) State the transformation of energy which takes place in the following when current is drawn from them:

1. An electric cell
2. A generator. [2]

(ii) What is a rectifier? Give a reason why the diode valve is used as a rectifier. [2]

(h) (i) You have just paid the electricity bill for your house.
a. What was that your family consumed, for which you had to pay?
b. In what unit was it measured? [2]

(ii) What quantity of heat will be produced in coil of resistance 80 ohm if current of 3A is passed through it for 4 seconds? [2]

(i) (i) What are high tension wires? Give two characteristics of these types of wires. [2]

(ii) Why is the filament of the electric iron or electric kettle put between mica sheets? [2]

(j) (i) Explain briefly how a fuse protects an electric circuit? [2]

(ii) What is earthing? What is its use? [2]

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

Question 2
(a)

1. Which class of levers has a mechanical advantage always less than one? Explain briefly with a diagram why their mechanical advantage is less than one. [2]
   
2. The crow-bar is a type of lever as shown alongside: A crow bar of length 150 cm has its fulcrum at a distance of 25 cm. from the load. Calculate the mechanical advantage of this crow bar. [2]

(b) (i) What is meant by a 'faulty balance'? [1]

(ii) A machine is driven by a 100 kg mass that falls 8.0 m in 4.0 s. It lifts a load of mass 500 kg vertically upwards. [5]

1. What is the force in Newtons, exerted by the falling mass?
2. What is the work done by 100 kg mass falling through 8·0 m?
3. What is the power input to the machine?
4. If efficiency of the machine is 75% or 0.75 , what is the power output of the machine?
5. What is the work done by the machine in 4.0 s? (Take g = 10 m/²).

Question 3
(a)

1. 2 kg of ice melts when a jet of steam at 100°C is passed through a hole drilled in a block of ice. What mass of steam was used? Given: Specific heat capacity of water = 4,200 J/kg/°C Specific latent heat of fusion of ice = 336 × 103 j/kg. Specific latent heat of vaporisation of steam = 2,268 × 103 j/kg. [4]
2. Why does evaporation always produce cooling? [2]

(b) (i) Explain why the surroundings become pleasantly warm when water in a lake starts freezing in cold countries. [2]

(ii) If, in a central heating system, steam enters a radiator pipe at 100°C and haves the radiator pipe at 100°C, can this radiator pipe heat a room? Give an explanation for your answer. [2]

Question 4
(a) Water in a pond appears to be only three quarters of its actual depth.

1. What property of light is responsible for this observation? [1]
2. Illustrate your answer with the help of a ray diagram. [2]

(b) (i) The critical angle for the glass of which the equilateral prism ABC is made, is 48⁰. A ray of light incident on the side AB of the prism is refracted along DE such that the angle it makes with the side AC is 138°. Also, ∠EDB = 90°. Copy the diagram.
a. Draw the path of the ray incident on the side AB. (Which travels along DE.)
b. Show the path along which the ray DE travels from the point E onwards and through the side BC. [3]

(ii) Which two conditions must be fulfilled for total internal reflection of light to occur? [2]

(iii) Write the names of (1) the most sensitive; (2) the most insensitive part of the retina. [2]

Question 5
(a)

1. Under what condition does the resonance occur? [1]
2. Why is a loud sound heard at acoustic resonance? [1]
3. How are colour, wavelength and frequency of light dependent on one another? [2]

(b) (i) A certain sound has a frequency of 256 hertz and a wavelength of 1 .3 m. Calculate the speed with which these sound travels. [2]

(ii) What difference would be felt by a listener between this sound and another sound travelling at the same speed but of wavelength 2.6 m? [1]

(iii) What rays exist beyond the visible-red end of the electromagnetic spectrum? State one use and one method of detecting these rays? [3]

Question 6
(a) The diagram given shows a battery of e.m.f. 9V and internal resistance 0.6Ω connected to three resistors A, B and C.

1. Calculate the combined resistance of B and C. [1]
   
2. Calculate the total resistance of A, B and C. [1]
3. Calculate total resistance of the circuit. [1]
4. Calculate the current in each of the three resistors—A, B and C. [3]

(b) (i) Draw a labelled diagram of the device you would use to transform 200 volts a.c. to 15 volts a.c.? [2]

(ii) What is the name of this device? [1]

(iii) State the principle on which a Voltmeter/Galvanometer works. [1]

Question 7

(a) What is an electromagnet? State two ways by which the strength of electromagnet can be increased. [3]

(b) (i) What is the main difference between fission reaction and fusion reaction? Give one example of each. [3]

(ii) An atomic nucleus denoted by _ZX^A emits an alpha particle. Write an equation to show the formation of the daughter product. [2]

(c) Mention two properties and two uses of X-rays. [2]