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Pre Board I Examination / Grade X / PHYSICS / 25th November, 2024 / Monday/ Morning _______________________________________________________________________________________ Maximum Marks: 80 Time allowed: two hours Ms. Neelam Rawat / Mr. Rajeev Rana: 45 _______________________________________________________________________________________ Answers to this paper must be written on the paper provided separately. You will not be allowed to write during the first 15 min. 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 A is compulsory. Attempt any four questions from Section B. The intended marks for questions or parts of questions are given in brackets [ ]. _______________________________________________________________________________________ SECTION A (Attempt all questions from this Section.) Question 1 Choose the correct answers to the questions from the given option: (i) [15] S is a radioactive source emitting , and -radiations. Y is a sheet of aluminium 2 cm thick placed 10 cm from S. Which radiations can be detected at G? a) only b) and only c) and d) only (ii) Gamma rays have frequency . that of X rays. a) Equal to b) Larger than c) Smaller than d) Both (a) and (c). Page 1 of 10 (iii) Rivers which originate from the glaciers at high altitudes have a supply of water throughout the year. This is because ice in high mountains does not melt all at once. This is due to: a) high specific heat of ice b) low specific heat of ice. c) low specific latent heat of fusion of ice. d) high specific latent heat of fusion of ice (iv) Observe the figure given below. Which of the following will happen if the magnet is brought closer to the solenoid? a) The galvanometer will deflect towards right. b) The galvanometer will deflect towards left. c) The galvanometer will fluctuate with equal frequency. d) The galvanometer will remain same. (v) A prism ABC (with BC as base) is placed in different orientations. A narrow beam of white light is incident on the prism as shown in Figure. In which of the following cases, after dispersion, the third colour from the top corresponds to the colour of the sky? a) (i) b) (ii) c) (iii) d) (iv) (vi) Consider the given figure and answer the question. Which is the key difference between the working principle of Fuse and Circuit Breaker ? a) Permanent melting of wire and switching mechanism. b) Circuit breaker is very expensive as compared to the fuse. c) Fuse has non metallic casing whereas circuit breaker has a metallic casing. d) None of the above. Page 2 of 10 (vii) Which type of lever has velocity ratio and mechanical advantage always less than one? a) Class I lever b) Class II lever c) Class III lever d) None of the above (viii) Assertion (A): The rainbow is a natural spectrum of sunlight in the sky. Reason (R): Rainbow is formed in the sky when the sun is overhead and water droplets are also present in air. a) Both A and R are true and R is correct explanation of the A. b) Both A and R are true but R is not the correct explanation of the A. c) A is true but R is false. d) A is false but R is true. (ix) The resultant moment of couple, if two equal forces each of 6 N are acting at a distance of 3 cm each from the centre is : a) 36 Nm b) 3.6 Nm c) 360 Nm d) 0.36 Nm (x) In which of the following postures the centre of gravity will be outside the human body? a) Posture (A) b) Posture (B) c) Posture (C) d) In all the posture, centre of gravity will be inside the human body. (xi) The parent nucleus of the following reaction is : a) 210 85X b) 206 85X c) 206 82X d) 216 86X Page 3 of 10 (xii) Which type of energy conversion takes place in an electric DC motor? a) Electrical to kinetic energy b) Electrical to rotational energy c) Electrical to potential energy d) All of the above (xiii) The graph plotted for potential difference (V) against current (I ) for non ohmic resistor is... a) A curve passing through origin b) A straight line not passing through origin c) A straight line passing through origin d) A circle centred at the origin. (xiv) A stone is placed at the bottom of a water tank appears to be raised by 80 cm. If refractive index of water is 4/3, find the actual depth of stone from free water surface. a) 200 cm b) 320 cm c) 400 cm d) 360 cm (xv) In an oscillating pendulum, KE is .. at extremes. a) Zero b) Positive c) Negative d) Variable Question 2 (i) Complete the following by choosing the correct answers from the bracket: [6] a) During change of state, ... [ temperature and volume / volume and mass / mass and temperature ] remains constant. b) When a charge moving in a magnetic field, in a direction other than the direction of magnetic field it experience a force. This force is referred as ... [Lenz force / Lorentz force / Newton force]. c) During energy transformation some form of energy is given out without it being used anywhere, such energy is called . [ backup energy / stored energy / dissipated form of energy]. d) A person standing between two vertical cliffs hears two sounds one after 6 s and other 4 s later. The time for first echo is ... [ 4 s / 6 s / 10 s] and for second echo is ... [ 4 s / 6 s / 10 s]. e) Quartz prism does not absorb . [ IR / UV / microwave ] radiation. Page 4 of 10 (ii) Draw a graph of potential energy vs height for a body thrown vertically upwards. [Assume [2] no friction is present.] (iii) a) Two wires AB and CD of same length are stretched by same amount. Which wire will [2] produce sound of greater pitch on plucking? b) Give a reason for your answer. Question 3 (i) The diagram below shows an object O placed in front of a convex lens. Redraw and [2] complete the ray diagram showing the formation of the image. (ii) a) Give the new convention for the colour code of live wire. [2] b) Two components in a circuit are always connected in series with the live wire. Name any one of them. (iii) Name the rules to determine the direction of a: [2] a) magnetic field produced around a current carrying straight conductor. b) Force experienced by a current carrying straight conductor placed in a magnetic field which is perpendicular to it. (iv) A solid of mass 50 g at 150 is placed in 100 g of water at 11 , when the final [2] temperature recorded is 20 . Find the specific heat capacity of the solid. (Specific heat capacity of water = 4.2 J/g/ ) (v) For a science exhibition, two students A and B brought two similar exhibits. Both the [2] exhibits consist of a coil placed in the magnetic field. Student A rotates the coil and a bulb connected to it glows. Student B passes current through the coil and the coil rotates. a) Name the phenomena involved with the exhibit of student A. b) State the principle based on which the exhibit of student B works. Page 5 of 10 (vi) Only one isotope of gold occurs naturally on Earth. There are several artificially produced [2] isotopes of gold. Gold-198 ( 198 Au) is an artificial isotope which is used in medicine and 79 in scientific research. Gold-198 decays by (beta)-emission to a stable isotope of mercury. Determine the number of protons and the number of neutrons in a nucleus of this isotope of mercury. (vii) a) An isotope of beryllium, Be, has the nuclide notation: 9 Be. The diagram shows one 4 [3] atom of this isotope. State the names for X and for Y. b) Which radiation produces maximum biological damage? SECTION B (Attempt any four questions from this Section.) Question 4 (i) Study the data given below showing the focal length of three convex lenses A, B and C [3] and the respective distances of objects placed in front of the lenses: Case Lens Focal Length (cm) Object Distance (cm) 1 A 20 45 2 B 15 30 3 C 30 20 a) In which one of the above cases the mirror will form a diminished image of the object? b) What is the nature and size of the mage formed by mirror C? (ii) a) A violet ray of light is directed from air to a glass block. The speed of light in air and 8 -1 8 [3] -1 in glass is 3 x 10 ms and 2 x 10 ms respectively. Calculate the refractive index of glass. b) If the wavelength of violet colour is 450 nm in air, calculate its wavelength when it enters the glass block. c) What will be the ratio of frequency of the violet light in air to frequency of the violet light in glass? Page 6 of 10 (iii) [4] The above diagram shows a glass prism of a critical angle 42 . a) Redraw the diagram and complete the path of the light ray PQ till it emerges out of the prism. b) Also, calculate the angle of incidence of the ray PQ for the face AB of the prism. Question 5 (i) An object is placed at a distance of 30 cm from a concave lens having the focal length of [3] 30 cm. a) Use lens formula to determine the distance of the image from the lens. b) Draw a labelled diagram to justify your answer of part (a). (ii) An electromagnetic radiation is used for photography in fog. [3] a) Identify the radiation. b) Why is this radiation mentioned by you, ideal for this purpose? c) In the atmosphere which coloured light scatter the most? (iii) Figure below shows the refraction and emergence of a ray of light incident on a [4] rectangular glass slab. a) Redraw the diagram and mark the lateral displacement of the incident ray. b) Name the two factors on which the lateral displacement depends. c) Which coloured light will travel fastest in this glass slab? Page 7 of 10 Question 6 (i) A uniform metre rule can be balanced at 60 cm mark if 100 g mass is hung at 80 cm mark. [3] a) Draw the diagram of the arrangement b) Find the mass of the metre rule c) In which direction the rule will tilt if 100 g mass is shifted from 80 cm to 85 cm? (ii) The weights of two bodies are 2 N and 2 kgf respectively. [3] a) What is the mass of each body? b) Calculate the ratio of work done on both bodies in lifting them through a height of 5 m. (Take g = 10 m/s2) (iii) a) What is the law of conservation of energy? [4] b) A ball of mass 4 kg is thrown vertically upwards with a velocity of 20 m/s. Find its kinetic energy, potential energy and total energy at the maximum height above the ground. (Take g = 10 m/s2) Question 7 (i) A block and tackle system of pulleys has a velocity ratio 5. a) [3] Draw a labelled diagram of the system indicating clearly the points of application and directions of load and effort. b) What is the mechanical advantage of the given system of pulleys if its efficiency is 80 %? (ii) a) A man stands between two high rise buildings and blows a whistle. He hears two [3] successive echoes after 0.4 s and 0.6 s. Calculate the distance between the two buildings [ speed of sound is 330 m/s]. b) Name the type of waves used for echo depth sounding. (iii) A transformer is used to transmit electrical energy from the generating station. A [4] transformer basically consists of a core, primary windings and secondary windings. It is an integral part of many low- power applications. Depending on the necessity, a step-up transformer or a step-down transformer is used in a circuit. a) For a step-up transformer, what can be predicted about the thickness of the primary coil with reference to that of the secondary coil. b) What is the working principle of a transformer? c) Draw a simple labelled diagram of step up transformer. d) The electrical energy transmission from a generating station is at high voltage. Why? Page 8 of 10 Question 8 (i) A piece of wire having a resistance R is cut into five equal parts. [3] a) How will the resistance of each part of the wire compared with the original resistance? b) If the five parts of the wire are placed in parallel, how will the resistance of the combination compare with the resistance of the original wire? c) What will be ratio of resistance in series to that of parallel? (ii) A radioactive nucleus X emits an alpha particle followed by two beta particles to form [3] nucleus Y. a) With respect to the element X, where would you position the element Y in the periodic table? b) What is the general name given to the element X and Y? c) If the atomic number of Y is 80 then what is the atomic number of X? (iii) Consider the circuit diagram below to answer the questions that follows. [4] a) Calculate resistance of the circuit when the key K is : I. Open II. Closed b) What is the reading in the ammeter A? c) Find the value of current through the 4 resistor. Question 9 (i) Calculate the mass of ice needed to cool 150 g of water contained in a calorimeter of mass [3] 50 g at 32 C such that the final temperature is 5 C. Specific heat capacity of calorimeter = 0.4 J/g C. Specific heat capacity of water = 4.2 J/g C Latent heat capacity of ice = 330 J/g. Page 9 of 10 (ii) The variation in temperature with time of heating of a piece of ice at constant rate is shown [3] in the given graph. Answer the following from the graph: a) What is represented by the part AB ? b) What does the part BC represent ? c) What conclusion do you draw regarding the nature of ice from the graph ? (iii) In a hydraulic power station, water is first stored in a dam at a higher altitude. a) [4] What is the purpose of water being stored at higher altitudes? b) When the water is allowed to fall on a turbine, what change of energy takes place for the water? c) Why is this turbine connected to the armature of a generator? d) Which basic law of physics is followed by the whole mechanism? ----------------------------------------------------- ALL THE BEST ----------------------------------------------------- Page 10 of 10
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