Friday, May 31, 2013

MODEL QUESTION PAPER For Class XII SCIence -Physics

MODEL QUESTION PAPER



Higher Secondary – Second Year – Physics



Time : 3 hrs. Mark : 150



PART – I



Note : (i) Answer all the questions. 30 x 1 = 30



(ii) Choose and write the correct answer.



(iii) Each question carries one mark.



1. A dipole is placed in a uniform electric field with its axis parallel to the field.



It experiences



(a) only a net force (b) only a torque



(c) both a net force and torque (d) neither a net force not a torque



2. The unit of permittivity is



(a) NC−2



(c) C2



3. The number of lines of force that radiate outwards from one coulomb charge



is



(a) 1.13 × 10



(c) 9 × 10



4. On moving a charge of 20 C by 2 cm, 2J of work is done, then the potential



difference between the points is



(a) 0.5 V (b) 0.1 V



(c) 8 V (d) 2 V



5. In the case of insulators, as the temperature decreases, resistivity



(a) increases (b) decreases



(c) becomes zero (d) remains contant



6. In a tangent galvanometer, for a constant current, the deflection is 30



plane of the coil is rotated through 90



deflection will be



(a) 0



(c) 60



7. In a thermocouple, the temperature of the cold junction is 20



temperature of inversion is 520



(a) 500



(c) 270



m−2



N−1



m−2



(b) Hm−1



(d) Nm2



C−2



11



9



(b) 8.85 × 10



(d) infinite



−11



. Now, for the same current, the



o



o



o



(b) 30



(d) 90



o



o



C. The neutral temperature is



o



C (b) 540



o



C (d) 510



o



o



C



C



o



6



8. Electromagnetic induction is not used in



(a) transformer (b) room heater



(c) AC generator (d) choke coil



9. Which of the following devices does not allow d.c. to pass through?



(a) resistor (b) capacitor



(c) inductor (d) all the above



10. The unit henry can also be written as



(a) VA−1



(c) wb A



11. In an AC circuit, the current I = I



e = Eo



(a) 0 (b)  π/4



(c)  π/2 (d)  π



12. In an electromagnetic wave, the phase difference between electric field and



magnetic field is



(a) 0 (b)  π/4



(c)  π/2 (d)  π



13. Of the following, which one is a biaxial crystal?



(a) tourmaline (b) ice



(d) calcite (d) mica



14. If the wavelength of the light is reduced to half, then the amount of



scattering will



(a) increase by 16 times (b) decrease by 16 times



(c) increase by 256 times (d) decrease by 256 times



15. A Nicol prism is based on the principle of



(a) refraction (b) reflection



(c) double refraction (d) diffraction



16. The ratio of radii of the first three Bhor orbits is



(a) 1 : 2 : 3 (b) 1 :



(c) 1 : 8 : 27 (d) 1 : 4 : 9



s (b)  Ωs



−1



(d) all



 sin (ωt –  π/2) lags behind the emf



o



 sin (ωt +  π/2) by



1



1



 :



2



3



7



17. In hydrogen atom, which of the following transitions produce a speetral line



of maximum frequency?



(a) 2 →1 (b) 6 →  2



(c) 4 → 3 (d) 5 →  2



18. In Millikan’s experiment, an oil drop of mass 4.9 × 10-14 kg is balanced



by applying a potential difference of 2 kV between the two plates which are



2 mm apart. The charge of the drop is



(a) 1.96 × 10



(c) 12 C (d) 4.9 × 10



19. If the potential difference between the cathode and the target of coolidge



tube is 1.24 × 10



is



(a) 10Å (b) 1Å



(c) 0.1Å (d) 0.01Å



20. The photoelectric effect can be explained on the basis of



(a) corpuscular theory (b) wave theory



(c) electromagnetic theory (d) quantum thery



21. The wavelength of the matter wave is independent of



(a) mass (b) velocity



(c) momentum (d) charge



22. The time taken by the radioactive element to reduce to 1/e times is



(a) half life (b) mean life



(c) half life/2 (d) twice the mean life



23. The ionisation power is maximum for



(a) neutrons (b) alpha particles



(c) gamma rays (d) beta particles



24. When



residual nucleus is



(a)



3



(c)



1



25. In a nuclear reactor cadmium rods are used to



(a) speed up neutrons (b) slow down neutrons



(c) absorb neutrons (d) remove heat



–18



 C (b) 1.602 × 10



–19



–19



  C



  C



5



V, then the minimum wavelength of continuous x−rays



B10



5



7



Li



H3



 is bombarded with neutron and  α−particle is emitted, the



H2



(b)



1



(d)



He



2



4



8



26. In a Colpitt’s oscillator circuit



(a) capacitive feedback is used (b) tapped coil is used



(c) no tuned LC circuit is used (d) no capacitor is used



27. An example of n−type semiconductor is



(a) pure germanium (b) pure silicon



(c) silicon doped with phosphorus (d) germanium doped with boron



28. What will be the input of A and B for the Boolean experession



(A + B ) . (A . B) = 1?



(a) 0, 1 (b) 1, 0



(c) 0, 0 (d) 1, 1



29. In T.V. transmission, the picture should not be scanned during the return



journey of the scanning. This is done by



(a) blanking pulse (b) saw tooth potential



(c) horizontal synchronising pulse (d) vertical synchronising pulse



30. Through which mode of propagation, the radio waves can be sent from one



place to another



(a) Ground wave propagation (b) Sky wave propagation



(c) Space wave propagation (d) All the above



PART – II



Note :  (i) Answer any 15 questions. 15 x 3 = 45



31. State coulomb’s law in electrostatics.



32. Why is it safer to be inside a car than standing under a tree during lightning?



33. What are the advantages of secondary cells?



34. The resistance of a nichrome wire at 0



of resistance is 0.004/



35. What is called superconductivity?



36. Define; amperein terms of force.



37. What happens to the value of current in RLC series circuit, if freqency of the



source is increased?



38. If the rate of change of current of 2 As



what is the self inductance of the solenoid?



39. Why does the sky appear blue in colour?



40. The refractive index of the medium is  √3. Calculate the angle of refraction if



the unpolarised light is incident on it at the polarising angle.



C is 10  Ω. If its temperature coefficient



o



C, find its resistance at boiling point of water.



o



−1



 induces an emf of 10 mV in a solenoid,



9



41. State the postulates of Bohr atom model.



42. In Bragg’s spectrometer, the glancing angle for first order spectrum was



observed to be 8



the x−ray is 0.7849Å.



43. Mention any threee applications of photo electric cells.



44. What is  α – decay? Give an example.



45. Define: Curie



46. Draw the block diagram of an oscillator and mention the components.



47. The gain of the amplifier is 100. If 5% of the output voltage is fedback into the



input through a negative feed back network, find out the voltage gain after



feedback.



48. Mention the advantages of ICS.



49. Define the input impedance of a transistor in CE mode.



50. What is meant by skip distance?



. Calculate the crystal lattice spacing, if the wavelength of



o



Part – III



Note : (i) Answer the question 60 compulsorily. 7 x 5 = 35



(ii) Of the remaining 11 questions, answer any six questions.



(iii) Draw diagrams wherever necessary



51. The plates of a parallel plate capacitor have an area of 90 cm2



separated by 2.5 mm. The capacitor is charged by connecting it into a 400 V



supply. How much electrostatic energy is stored by the capacitor.



52. Obtain the condition for bridge balance in Wheatstone’s bridge.



53. Explain the method to compare the emfs of two cells using potentiometer.



54. A circular coil of 50 turns and radius 25 cm carries a current of 6A. It is



suspended in a uniform magnetic field of induction 10



plane of the coil makes an angle of 60



coil.



55. Explain the various energy losses in a transformer.



56. Derive the expression for the radius of the n



57. Explain the spectral series of hydrogen atom.



58. Obtain Einstein’s photo electric equation.



59. Establish Einstein’s mass-energy equivalence, E = mc



−3



T. The normal to the



o



 with the field. Calculate torque of the



th



 dark ring.



2



.



10



60. Calculate the binding energy and binding energy per nucleon of



Given, mass of 1 proton = 1.007825 amu; mass of 1 neutron = 1.008665 amu;



mass of



40



Ca



20



 nucleus = 39.96259 amu.



Or



Calculate the mass of coal in ton required to produce the same energy as



that produced by the fission of 1 kg of U235



coal = 33.6 × 10



U235



61. Draw the frequency response curve of single stage CE amplifier and discuss



the results.



62. Draw the functional block diagram of AM radio transmitter.



6



 J/kg ; 1 ton = 1000 kg ; Energy per fission of



 = 200 MeV ; Avagadro number = 6.023 × 10



. Given : Heat of combustion of



23



.



PART – IV



Note : (i) Answer any 4 questions in detail. 4 x 10 = 40



(ii) Draw diagrams wherever necessary



63. What is an electric dipole? Derive an expression for the electric field due to



an electric dipole at a point on its axial line.



64. Discuss the motion of a charged particle in a uniform magnetic field.



65. Discuss with theory, the method of inducing emf in a coil by changing its



orientation with respect to the direction of the magnetic field.



66. What is known as interference? Derive an expression for bandwidth of



interference fringes in young’s double slit experiment.



67. With the help of energy level diagram explain the working of He−Ne laser.



68. Describe Bainbridge mass spectrometer to determine the isotopic masses of



nuclei.



69. What is known as rectification? Explain the bridge rectifier.



70. With the help of block diagram, explain the monochrome TV receiver.

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