ICSE Class 10 Physics Previous Year Question Paper 2018

Question 1

(a)
    (i) State and define the SI unit of power.
    (ii) How is the unit hose power related to the S.I. 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  o A and 8000   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  Where K: kinetic energy, V: Linear velocity....

Question 2

(a)The power of a lens is - 5D.
    (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.

Question 3 

 (a) Displacement distance graph of 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 2Ω, 3Ω and 5Ω. How will you join them so that the total resistance is more than 7Ω?
     (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 iv the advantage of producing 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 e.m.f. 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?

Question 4

(a) 
  (i) Flow can a temperature in degree Celsius be converted into S.I. unit of temperature?
  (ii) A liquid X has the maximum specific heat capacity and is used as a coolant in Car radiatrs. Name the liquid X.

(b)A solid metal weighing 150 g melts at its melting point of 800 °C by providing heat at the rate of 100 W. The time taken for it to     completely melt at the same temperature is 4 min. 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.

Question 5

(a) 
(i) Derive a relationship between S.I. and C.C.S. unit of work.
(ii) A force acts on a body and displaces it by a distance S in a direction at an angle θ with the direction of force. What should be       the value of θ to get the maximum positive work?

(b)A half metre rod is pivoted at the centre with two weights of 20gf and 12gf suspended at a perpendicular distance of 6 cm and    10 cm from the pivot respectively as shown below.

(i) Which of the two forces acting on the rigid rod causes clockwise moment?
(ii) Is the rod in equilibrium?
(iii) The direction of 20 kgf force is reversed. What is the magnitude of the resultant moment of the forces on the rod?

(c) 
(i) Draw a diagram to show a block and tackle pulley system having a velocity ratio of 3 marking the direction of load(L), effort(E) and tension(T).
(ii) The pulley system drawn lifts a load of 150 N when an effort of 60 N is applied. Find its mechanical advantage.
(iii) Is the above pulley system an ideal machine or not?

Question 6

(a)A ray of light X Y passes through a right angled isosceles prism as shown below.

(i) What is the angle through which the incident ray deviates and emerges out of the prism?
(ii) Name the instrument Whore this action of prism is put into use.
(iii) Which prism surface will behave as a mirror?

(b)An object AB is placed between O and F1 on the principal axis of a converging lens as shown in the diagram.

Copy the diagram and by using three standard rays starting from point A, obtain an image of the object AB.

(c) An object is placed at a distance of 12 cm from a convex lens of focal length 8 cm. Find:
(i) the position of the image
(ii) nature of the image

Question 7

(a)Draw the diagram of a right angled isosceles prism which is used to make an invented image erect.

(b)  

The diagram above shows a wire stretched over a sonometer. Stems of two vibrating tuning forks A and B are touched to the wooden box of the sonometer. It is observed that the paper rider (a small piece of paper folded at the centre) present on the wire files off when the stem of vibrating tuning fork B is touched to the wooden box but the paper just vibrates when the stem of vibrating tuning fork A is touched to the wooden box.
(i) Name the phenomenon when the paper rider just vibrates.
(ii) Name the phenomenon when the paper rider flies off.

(iii) Why does the paper rider fly off when the stem of tuning fork B is touched to the box?

(c) A person is standing at the sea shore. An observer on the ship which is anchored in between a vertical cliff and the person on the shore fires a gun. The person on the shore hears two sounds, 2 seconds and 3 seconds after seeing the smoke of the fired gun. If the speed of sound in the air is 320 ms^-1 then calculate:

(i) the distance between the observer on the ship and the person on the shore.
(ii) the distance between the cliff and the observer on the ship.

Question 8

(a) 
  (i) A fuse is rated 8A. Can it be used with an electrical appliance rated 5 KW, 200 V? Give a reason.
  (ii) Name two safety devices which arc connected to the live wire of a household electric circuit.

(b)
  (i) Find the equivalent resistance between A and B.

  (ii) State whether the resistivity of a wire changes with the change in the thickness of the wire.

(c) An electric iron is rated 220V, 2kW.
  (i) if the iron is used for 2h daily find the cost of running it for one week if it costs ` 4.25 per kWh.
  (ii) Why is the fuse absolutely necessary in a power circuit?

Question 9

(a)
   (i) Heat supplied to a solid changes it into liquid. What is this change in phase called?
  (ii) During the phase change does the average kinetic energy of the molecules of the substance increase?
  (iii) What is the energy absorbed during the phase change called?

(b) 
  (i) State two differences between "Heat Capacity" and "Specific Heat Capacity".
  (ii) Give a mathematical relation between Heat Capacity and Specific Heat Capacity.

(c) The temperature of 170g of totter at 50°C is lowered to 5°C by adding certain amount of ice to it. Find the mass elite added.
     Given: Specific hest capacity of water = 4200 J kg^-1°C^-1 and Specific latent heat of ice = 336000 J kg^-1

Question 10

(a) 

The diagram shows a coil wound around a U shape soft iron bar AB.
(i) What is the polarity induced at the ends A and B when the switch is pressed?
(ii) Suggest one way to strengthen the magnetic field in the electromagnet.
(iii) What will be the polarities at A & B if the direction of current is reversed in the circuit?

(b)The ore of Uranium found in nature contains 92U²³⁸ and 92U²³⁵. Although both the isotopes are fissionable, it is found out experimentally that one of the two isotopes is more easily fissionable.
(i) Name the isotope of Uranium which is easily fissionable.
(ii) Give a reason for your answer.
(iii) 'Write a nuclear reaction when Uranium 238 emits an alpha particle to form a Thorium (Th) nucleus.

(c) Radiations given out from a source when subjected to an electric field to n direction perpendicular to their path arc shown below in the diagram. The arrows show the path of the radiation A, B and C. Answer the following questions in terms of A, B and C.

(i) Name the radiation B which is unaffected by the electrostatic field.
(ii) Why does the radiation C deflect more than A?
(iii) Which among the three causes the least biological damage externally?
(iv) Name the radiation which is used in carbon dating.

Answer 1

(a)
(i) The SI unit of power is watt. It is denoted by the symbol W.
(ii) 1 horsepower = 746 watt

(b)
(i) An electric iron
    Electrical energy is converted to heat energy.
(ii) A ceiling fan
    Electrical energy is converted to mechanical energy.

(c) Diagram of a lever in use:

(i) The load is in between the effort and the fulcrum. So, this is a class II lever.
(ii) If the load arm is shifted towards the fulcrum, the length of the load arm decreases. Mechanical advantage is equal to the ratio       of the length of the effort arm to the length of the load arm. Hence, mechanical advantage increases.

(d)
    (i) Both light of given wavelengths are electromagnetic waves.
        Electromagnetic waves will travel at the same speed in vacuum irrespective of its wavelength.
    (ii) Speed is the product of frequency and wavelength. Since speed is constant, light of lower wavelength 4000 A⁰ will have         higher frequency.

(e)
(i) Although speed remains constant, its direction keeps on changing. Hence, its velocity which is displacement in a specified direction changes, and due to this, the movement in a circular path is said to be accelerated.
(ii)

Where K is kinetic energy and V is linear velocity.

Where m is mass. Its SI unit is kg.

Answer 2

(a)
   (i) The power of a lens is −5 D.
       Focal length = 100/(−5) = −20 cm.
   (ii) Since focal length is negative, the lens is a concave lens.

(b)
   (i) It produces a real and same size image of the object.
       Thus, the object is at 2F1.
   (ii) It is used as a magnifying lens.
        The object is between F1 and the optical centre.

(c)
  (i) If the critical angle is C and μ is the absolute refractive index, then
    sin C = 1/μ
  (ii) Red light has a higher critical angle because the refractive index of red
        light is smaller than that of green light.

(d)
   (i) Scattering is the process of absorption and re-emission of light energy.
   (ii)
    1. Molecules of smoke are bigger than the wavelength of light - True.
    2. Molecules of smoke are smaller than the wavelength of light - False.

(e)The following diagram shows a 60°, 30°, 90° glass prism of critical angle 42°.

Answer 3

(a)

(i) Amplitude of Wave A is 20 cm. Amplitude of Wave B is 10 cm.
(ii) Wavelength of B is twice the wavelength of A.

(b)
(i) 

(ii) We have to connect them in a series to get equivalent resistance:
2 Ω + 3 Ω + 5 Ω = 10 Ω

(c)
(i) Nuclear fusion is the process in which two light nuclei combine to form a heavy nucleus. In this process, a huge amount of energy is released.
(ii) For the same mass, the energy released in a fusion process is more than that released in a fission process. A fusionable substance is found in bundance. These substances are not radioactive and do not give any harmful radiation. Disposal of waste is not difficult.0

(d)
(i) Periodic vibrations of the body in the absence of any external force on it are called natural or free vibrations.
(ii) The amplitude of a vibrating body continuously decreases during damped vibration because of the frictional or resistive force due to the urrounding.

(e)
(i)

(ii) Transformer runs on alternating current.

Answer 4

(a)
(i) K = C + 273
   ‘C’ is the temperature in degree Celsius and ‘K’ is the temperature in Kelvin, which is the SI unit.
(ii) Liquid ‘X’ is water.

(b)
Energy absorbed for melting in 4 min = 100 × 4 × 60 = 24000 J
Specific latent heat of fusion of the metal = 24000/0.150 = 160 kJ/kg

(c)
(i) The wire also called the phase wire is a live wire.
(ii) The wire connected to the top terminal of a three-pin socket is the earthing wire.

(d)
(i) Isobars are two nuclei having the same atomic number Z but different mass numbers.
(ii) Examples:

(e)
(i) A strong magnetic field is created using an electromagnet, whereas a permanent magnet gives a weak magnetic field.
(ii) The magnetic field of an electromagnet can be controlled by current, whereas the magnetic field of a permanent magnet cannot be changed.

Answer 5

(a)
(i) Relationship between SI and CGS units of work:
Work is force F times displacement d.
W = F × d
CGS units: [F][d] = [dyne][cm] = [erg]
1 newton = 10⁵ dyne
1 m = 100 cm
I joule = 1 newton × 1 m = 10⁵ dyne × 100 cm = 10⁷ erg

(ii)
Work = force (F) × displacement in the direction of force
Work = F × S × cos (θ)
Here, θ is the angle between force F and displacement S.
To get maximum work, cos (θ) = 1 or θ= 0

(b)

(i) 12 gf acting on the rigid rod causes clockwise moment.
(ii) Yes, the rod is in equilibrium because both clockwise and anti-clockwise moments are the same.
(iii) If 20 gf is reversed, both forces give clockwise moment.
     Total clockwise moment is 2 × 120 × 9.8 × 10−3 N-m = 2.352 N-m

(c)
(i) Diagram of a block and tackle pulley system with a velocity ratio of 3 marking the direction of load (L), effort (E) and tension (T).

(ii) Mechanical Advantage = Load/Effort = 150/60 = 2.5
(iii) Although theoretical efficiency is 100% for the block and tackle system of pulleys, mechanical advantage decreases due to friction in the bearings of the pulleys and the weight of the string and the lower block with pulleys. Efficiency decreases if mechanical advantage decreases.

Answer 6

(a) A ray of light XY passes through a right angled isosceles prism as shown below.

  (i) The angle of deviation is 90°.
  (ii) This action of the prism is used in periscopes.
  (iii) Surface AB functions as a mirror.

(b)An object AB is placed between O and F1 on the principal axis of a converging lens as shown in the diagram.

    Using three standard rays starting from point A, obtain an image of the object AB.

(c)

u = −12 ,
f = +8;
Hence, v = 24 cm
The image will be formed at 24 cm on the other side of the lens. The image is inverted, real and magnified [m = 24/ (−12) = −2].

Answer 7

(a)Right angled isosceles prism used to make an inverted image erect.

(b)

(i) Forced vibration. Due to the vibrations of the tuning fork, vibrations are produced in surrounding air and this forces the string to vibrate.
(ii) Resonance. Frequency of tuning fork vibration is the same as the frequency of free vibrations of a string.
(iii) When the vibration frequency of a tuning fork is the same as the frequency of natural vibration of the string, resonance occurs and vibration amplitude of the string is maximum. Hence, the paper rider flies off.

(c)
(i) The distance between the observer on the ship and the person on the shore.
(ii) The distance between the cliff and the observer on the ship.

(i) The first sound heard at 2 seconds comes directly from the observer to the man. Hence, the distance of the observer to the sea shore is 2 × 340 = 680 m.
(ii) The second sound is due to an echo. Distance travelled by the sound is
680 + 2S, where S is the distance between the observer and the cliff.
680 + 2S = 5 × 340 = 1700 m. Hence, S = 510 m.

Answer 8

(a)
(i) Power = voltage × current
Current = power/voltage = 5000/200 = 25 A
But the fuse is rated 8 A; hence, the fuse cannot be used.
(ii)
(1) Fuse, (2) MCB (Miniature Circuit Breaker)

(b)
(i)

Effective resistance of a parallel combination of 6 Ω and 3 Ω resistors is given by
R1 = (6 × 3)/(6 + 3) = 2 Ω
Effective resistance of a parallel combination of 4 Ω and 12 Ω resistors is given by
R2 = (4 × 12)/(4 + 12) = 3 Ω
Equivalent resistance between A and B = 2 Ω + 3 Ω = 5 Ω
(ii) Resistivity is the property of a material and does not depend on the dimensions of the wire. Hence, resistivity does not change with a change in the thickness of the wire.

(c)
(i) An electric iron is rated 220 V, 2 kW.
Energy consumption in kWh = power (kW) × time (hr) = 2 × 7 × 2 = 28 kWh
Running cost = 28 × 4.25 = Rs 119
(ii) An electric fuse is a safety device which is used to limit the current in an electric circuit. The use of the fuse safeguards the circuit and the appliance connected in that circuit from being damaged.

Answer 9

(a)
(i) This phase change is called melting of the solid.
(ii) Since phase change takes place at constant temperature, the average
kinetic energy of the molecules of the substance will not change.
(iii) Energy absorbed during the phase change is called latent heat of fusion.

(b)
(i)

(ii) Mathematical relation between heat capacity and specific heat capacity: Specific heat capacity = heat capacity/mass

(c)
  Given: Specific heat capacity of water = 4200 J kg⁻¹°C⁻¹ and specific latent
  heat of ice = 336000 J kg⁻¹
  Heat loss by 170 g water H_L = 170 × 10⁻³ × 4200 × (50− 5) = 32130 joules
  Heat gain by mg of ice H_G = m × (336000 + 4200 × 5) = m × 357000 joules
  Mass of ice = 32130/357000 = 0.09 kg = 90 g

Answer 10

(a)

Diagram showing a coil wound around a U-shape soft iron bar AB.
(i) At A, current flows in the clockwise direction in the coil. Hence, by the clock rule, polarity induced at A is the South Pole.
    At B, current flows in the anti-clockwise direction in the coil. Hence, by the clock rule, polarity induced at B is the North Pole.
(ii) By increasing the current, the strength of the magnetic field intensity is increased.
(iii) If the direction of current is reversed, then polarity at A is the North Pole and polarity at B is the South Pole.

(b)
(i) ₉₂U²³⁵ is an isotope of uranium which is easily fissionable.
(ii) ₉₂U²³⁵ undergoes fission with low energy neutrons or thermal neutrons.
But for the fission process in ₉₂U²³⁸ ,fast neutrons of energy _˜1 MeV is required.
(iii) A nuclear reaction when Uranium -238 emits an alpha particle to form a Thorium (Th) nucleus is given by
 ₉₂U²³⁸  → ₉₂Th²³⁴ + ₂He⁴

(c) 

(i) Radiation B which is unaffected by the electrostatic field is gamma radiation.
(ii) Radiation C is beta radiation, and it is nothing but electrons. The mass of electrons is much smaller than alpha particles       (radiation A). Hence, beta radiation (radiation C) deflects more.
(iii) Radiation A, which is alpha radiation, causes the least biological damage externally.
(iv) Gamma radiation is used for carbon dating.