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## Physics 2018 Solved Question Paper ICSE Previous Year

• Answers to this Paper must be written on the paper provided separately.
• You will not be allowed to write during the first 15 minutes.
• This time is to be spent in reading the Question Paper.
• The time given at the head of this Paper is the time allowed for writing the answers.
• Section I is compulsory. Attempt any four questions from Section II.
• The intended marks for questions or parts of questions are given in brackets [ ].

### Physics 2018 Solved Question Paper ICSE Previous Year

Section – A [40 Marks]
(Attempt all questions from this Section)

Question 1

(a) (i) State and define the SI unit of power. 
(ii) How is the unit horse power related to the SI unit of power?
(b) State the energy changes in the following cases while in use: 
(i) An electric iron.
(ii) A ceiling fan.
(c) The diagram below shows a lever in use: 
(i) To which class of levers does it belong?
(ii) Without changing the dimensions of the lever, if the load is shifted towards the fulcrum what happens to the mechanical advantage of the lever? (d) (i) Why is the ratio of the velocities of light of wavelengths 4000 A and 8000 A in vacuum 1:1?
(ii) Which of the above wavelengths has a higher frequency? 
(e) (i) Why is the motion of a body moving with a constant speed around a circular path said to be accelerated?
(ii) Name the unit of physical quantity obtained by the formula 2K/V2 where K: kinetic energy, V: Linear velocity.

(a) (i) The SI unit of power is watt (W). The power of an agent is said to be one watt if it does one joule of work in one second.
(ii) 1 hp = 746 W

(b) (i) Electrical into heat energy

(ii) Electrical

(c) (i) Second class .
(ii)It increases

(d) (i) Because all wavelengths of light travel with the same velocity in vacuum
(ii) 4000 A

(e) (i) Because at every point of motion the direction of speed changes i.e., the body possesses velocity which changes with time.
(ii) J s -2 m -2

Question 2.

The power of a lens is -5D. 
(a) (i) Find its focal length.
(ii) Name the type of lens.
(b) State the position of the object in front of a converging lens if:
(i) It produces a real and same size image of the object.
(ii) It is used as a magnifying lens.
(c) (i) State the relation between the critical angle and the absolute refractive index of a medium.
(ii) Which colour of light has a higher critical angle? Red light or Green light. 
(d) (i) Define scattering. 
(ii) The smoke from a fire looks white. Which of the following statements is true?
1. Molecules of the smoke are bigger than the wavelength of light.
2. Molecules of the smoke are smaller than the wavelength of light.
(e) The following diagram shows a 60°, 30°, 90° glass prism of critical angle 42°. Copy the diagram and complete the path of incident ray AB emerging out of the prism marking the angle of incidence on each surface. (a) (i) f = $\frac { 1 }{ P }$ = $\frac { 1 }{ -5 }$ = -0.2 m = 20cm
(ii) Concave

(b) (i) 2F
(ii) Between F and 2F

(c) (i) n = $\frac { 1 }{ sin C }$
(ii) Red

(d) (i) Scattering is a general physical process where light is forced to deviate from a straight trajectory by one or more paths due to localized non-uniform in the medium through which it passes
(ii) Molecule of the smoke are bigger than the wavelength of the light.

(e) The diagram is as shown. Question 3.

(a) Displacement distance graph of the two sound waves A and B, travelling in a medium, are as shown in the diagram below. Study the two sound waves and compare their:
(i) Amplitudes
(ii) Wavelengths
(b) You have three resistors of values 2 Ω , 3 Ω and 5 Ω How will you join them so that the total resistance is more than 7 Ω? 
(i) Draw a diagram for the arrangement.
(ii) Calculate the equivalent resistance.
(c) (i) What do you understand by the term nuclear fusion? 
(ii) Nuclear power plants use nuclear fission reaction to produce electricity. What is the advantage ofproducing electricity by fusion reaction?
(d) (i) What do you understand by free vibrations of a body? 
(ii) Why does the amplitude of a vibrating body continuously decrease during damped vibrations?
(e) (i) How is the emf across primary and secondary coils of a transformer related with the number of turns of coil in them? 
(ii) On which type of current do transformers work?

(a) (i) AA/AB = 20/10 = 2
(ii) λB > λ

(b) (i) All of these can be connected in series as shown (ii) R = 5 + 3 + 2 = 10 Ω

(c) (i) K is a process in which two or more smaller nuclei combine to form a bigger nucleus.
(ii) There is no pollution in nuclear fusion.

(d) (i) $\frac{\mathrm{V}_{\mathrm{P}}}{\mathrm{V}_{\mathrm{S}}}$ = $\frac{\mathrm{N}_{\mathrm{P}}}{\mathrm{N}_{\mathrm{S}}}$
(ii) Alternating current

Question 4.

(a) (i) How can a temperature in degree Celsius be converted into SI unit of temperature? 
(ii) A liquid X has the maximum specific heat capacity and is used as a coolant in Car radiators. Name the liquid X.
(b) A solid metal weighing 150 g melts at its melting point of800 °C by providing heat at the rate of 100 W The time taken for it to completely melt at the same temperature is 4 mm. What is the specific latent heat of fusion of the metal? 
(c) Identify the following wires used in a household circuit: 
(i) The wire is also called as the phase wire.
(ii) The wire is connected to the top terminal of a three-pin socket.
(d) (i) What are isobars? 
(ii) Give one example of isobars.
(e) State any two advantages of electromagnets over permanent magnets. 

(a) (i) 1°C = 273 K
(ii) Water

(b) Using Q=mL, 100 x 4 x 60 x =150 x 10-3 x L or L = $\frac{100 \times 4 \times 60}{150 \times 10^{-3}}$ = L = 1.6 x 10J Kg-1

(c) (i) Live wire
(ii) Earth wire

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