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## All questions are compulsory

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**CBSE Sample Paper 2010-2011Physics**Time allowed: 3 hours Maximum Marks: 100 • All questions are compulsory • There is no overall choice. However, an internal choice has been provided in one question of two marks, one question of three marks and all three questions of five marks. You have to attempt only one of the choices in such questions. • Question numbers 1 to 8 are very short answer questions, carrying 1 mark each. • Question numbers 9 to 18 are short answer questions, carrying 2 marks each. • Question numbers 19 to 27 are short answer questions, carrying 3 marks each. • Question numbers 28 to 30 are long answer questions, carrying 5 marks each. • Use of calculators is not permitted. However, you may use log table if necessary. • You may use the following values of physical constants wherever necessary. • C = 3108 ms-1; h=6.6 10— 34‑Js; e=1.610-19C; Mass of neutron mn 1.610-27 kg • Boltzmann’s constant K =1.38 10-23 JK-1 • Avogadro’s number NA = 6.0231023/mole • Special Instructions: • . First fifteen minutes will be only to read the paper. Please start attempting the paper at 10:45 a.m. • . Attempt in any manner but please write the correct question number. • . Manage your time accordingly and try to attempt all the questions. • . Please write whatever is required in the answer sheet. • . Please checks that this question paper contains 30 questions • . First fill the OMR Sheet, then attempt the questions. About the Institute:-Pacific Group is recognized and renowned for its leadership in education and its contribution towards overall development of student since 1996. Pacific University is spread over 100 Acres of land. Pacific University is a global knowledge destination, education more than 20,000 students in multiple Engineering, Medical, Management, Pharmacy, Hotel Management, Media & Communication, Fashion Technology, Basic Degree Courses and other Streams.**A compass needles, pivoted about the horizontal axis and**free to move in the magnetic meridian, is observed to point along the • Vertical direction at a plane A. • Horizontal direction at a plane B. Give the value of the angle of dip at these two places. • Give the value of the threshold voltage for a (i) silicon diode (ii) germanium diode. • State the two functions performed by a modem. • An electron is moving with velocity v along the axis of a long straight solenoid carrying current I. What will be the force acting on the electron due to the magnetic field of the solenoid? • The figure given below shows the variation of an alternating emf with time. What is the average value of the emf for the shaded part of the graph? • Write unit of impedance. • What is the change in resistance of an Eureka wire when its radius is halved and the length is reduced to one fourth of its original value. • Draw energy band diagram for extrinsic semiconductor. • Give the nature of V-I graph for (i) ohmic (ii) non-ohmic circuit elements. Given one example of each type. • Name the phenomenon associated with the production of back emf in a coil due to change of electric current through the coil itself. Name and define the SI unit used for measuring this characteristic of the coil. • Fig. shows a 2.0 V potentiometer used for the determination of internal resistance of a 1.5 V cell. The balance point of the cell in open circuit is 76.3 cm. When a resistor of 9.5 is used in the external circuit of the cell, the balance point shifts to 64.8 cm. length of the potentiometer wire. Determine the internal resistance of the cell. • A given p-n junction is biased in two different ways as shown in the figure. Identify the type of biasing used in each case. What is the effect of these biasings on the barrier potential across the given p-n junction? • After 12th Admission – • 4 Years B. Tech • 5½ Years Integrated (B.Tech. + M.Tech.) • 5½ Years Integrated (B.Tech. + M.B.A.) • 2-Years M.Tech • Ph.D. Programmes in all Engineering Specialization • .**13. Find the position of the image formed by the lens shown**in the figure. Another lens is placed in contact with this lens to shift the image further away from the lens. What is the nature of the second lens? 14. A nucleus of mass M initially at rest splits into two fragments of masses (M>M’). Find the ratio of de-Broglie wavelengths of the two fragments. Or Calculate the ratio of de-Broglie wavelength associated with a Deutron moving with velocity 2v and an alpha particle moving with velocity v. 15. The output of an unregulated dc power supply needs to be regulated. Name the device that can be used for this purpose and draw the relevant circuit diagram. also draw its characteristic curve 16. The given figure shows a network of resistance. Name the circuit so formed. What is the current flowing in the arm BD of the circuit? State the two laws used to find the current in different branches of this circuit.**17. Write the relation between angle of incidence (i) the**angle of emergence (e), the angle of prism (A) and the angle of deviation () for rays undergoing refraction through a prism. What is the relation between i and e for rays undergoing minimum deviation? Using this relation obtain an expression for the refractive index () of the material of the prism in terms of A and angle of minimum deviation. 18. Define the terms (i) disintegration constant and (ii) half life of radioactive nucleus. Obtains the relation between the two. 19. Explain amplitude modulation. A modulating signal has zero dc component and peak to peak voltage of 11V. It is used to amplitude modulate a carrier of peak voltage of 10 V. Calculate the modulation index. 20. An electric dipole with moment is placed in a uniform electric field of intensity . Write the expression for the torque experienced by the dipole. Identify two pairs of perpendicular vectors in the expression. Show diagrammatically the orientation of the dipole in the field for which the torque is (i) maximum (ii) half the maximum value (iii) Zero. 21. Obtain an expression for the magnetic moment of an electron, moving with a speed ‘v’, in a circular orbit of radius ‘r’ . State the rule to find its direction. How does this magnetic moment change when (i) the frequency of revolution is doubled (ii) the orbit radius is halved? 22. Electromagnetic waves with wavelength • are used to treat muscular strain. • are used by a FM radio station for broadcasting. • are used to detect fracture in bones. • are absorbed by the ozone layer of the atmosphere. Identify and name the part of electromagnetic spectrum to which these radiations belong. Arrange these wavelengths in decreasing order of magnitude. 23.Define mass number (A) of an atomic nucleus. Assuming the nucleus to be spherical, give the relation between mass number (A) and the radius (r) of the nucleus. An electron and a photon each have a wavelength of 1.00 nm. Find (a) Their momenta (b) the energy of the photon and (c) the kinetic energy of electron. What is the ratio of the other magnitude of density of nuclear matter and density of ordinary matter? 24. For the transistor shown here, identify the (i) type of transistor used and (ii) biasing configuration employed. The output characteristics of he transistor, for this biasing configuration area as shown**Use these graph to estimate the value of the current**amplification factor for the transistor for VCE = 3V 26. Obtain an expression for the energy stored in a parallel plate capacitor. In the following figure, the energy stored in C4 is 27J. Calculate the total energy stored in the system. 27. Following figure shows an experimental set up similar to young’s double slit experiment to observe interference of light.**Here SS2 –SS1 =**Write the condition of (i) constructive (ii) destructive interference at any point P in term of path difference S2P – S1P.Does the central fringe observed in the above set up lie above or below O? Give reason in support of your answer. Yellow light of wavelength 6000 produces fringes of width 0.8 mm in Young’s double slit experiment. What will be the fringe width if the light source is replaced by another monochromatic source of wavelength 7500 and separation between the slits is doubled? OrDraw a graph showing the variation of intensity with angle in a single slit diffraction pattern. Explain why the intensity of the first secondary maximum is much less than that of the first secondary maximum is much less than that of the central maximum. Light of wavelength 6000 , is used to illuminate a slit of width 0.1 mm. Obtain the angular position of the first minimum in the resulting diffraction pattern. What will happen to the intensity of the central maximum if the width of the slit were to be reduced to 0.05 mm? 28. The given graphs (a) and (b) represent the variation of the opposition offered by the circuit elements to the low of alternating current, with frequency of the applied emf. Identify the circuit element corresponding to each graph. A circuit is set up by connecting L=100 mH, C=5 and R =100 in series. An alternating emf of of Hz is applied across this series combination. Calculated the impedance of the circuit. What is the average power dissipated in (a) the resistor (b) the capacitor (c) the inductor and (d) the complete circuit?**State Lenz’s Law. The energy E, required to build up a**steady current I, in a given coil, varies with I in the manner shown. Calculate the self inductance of the coil. A circular coil of radius r, is placed co-axially with another circular coil of radius R (R>>r) with the centres of the two coils coinciding with each other. Obtain an expression for the mutual inductance of this pair of coils. 29. State Gauss's Theorem.Apply this theorem to obtain the expression for the electric field at a point due to at infinitely long uniformly charged straight wire The electric field components in the fig. shown are Ex = x ½, Ey = Ez = 0, in which = 800 N/cm ½, Calculate (a) the electric flux through the cube (b) the charge within the cube. The side of cube a = 0.1 Describe the construction and working of a Van de Graaff generator with the help of a labeled diagram. Two charged conducting spheres of radii a and b are connected to each other by a conducting wire. What is the ratio of (i) charges on the spheres and (ii) electric fields at the surface of the two spheres. 30. Derive lens maker's formula for a double convex lens. State the assumptions made and sign convention used. A needle placed 45 cm. from the lens forms an image on a screen placed 90 cm on the other side of the lens. Identify the type of the lens and determine its focal length. What is the size of the image if the size of the needle is 5.0 cm. Or An angular magnification (magnifying power) of 30 is desired using an objective of focal length 1.25 cm and on eye-piece of focal length 5 cm. How will you set up the compound microscope? Show a labeled ray diagram showing the formation of image in a compound microscope. Write the expression for its magnifying power.