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Page 2 Sample Paper 05 CBSE Physics Class 12 5. A parallel plate capacitor is made by stacking n equally spaced plates connected alternatively. If capacitance between any two adjacent plates is C , then the resultant capacitance is (a) C (b) nC (c) ( ) n C - 1 (d) ( ) n C + 1 6. The magnetic lines of force inside a bar magnet (a) do not exist (b) are from north-pole to south-pole of the magnet (c) are from south-pole to north-pole of the magnet (d) depend upon the area of cross-section of the bar magnet 7. If a wire of length 2 m is moving with a velocity of 1 m s 1 - - perpendicular to a magnetic field of 0.5 T, then E.M.F. induced in the wire will be (a) 0.2 V (b) 0.5 V (c) 1 V (d) 2 V 8. The electric field at a distance 2 cm from the centre of a hollow spherical conducting shell of radius 4 cm having a charge of 2 10 3 # - C on its surface, is (a) zero (b) 1 1. V 10 m 10 1 # - - (c) 4 5. V 10 m 10 1 # - - - (d) 4 5. V 10 m 10 1 # − + − 9. Electron-volt (eV) is the measure of (a) charge (b) potential difference (c) current (d) energy 10. The frequency of X-rays is (a) 10 Hz 12 (b) 10 Hz 14 (c) Hz1016 (d) 10 Hz 18 11. The core of a transformer is laminated, so as to (a) make it light weight (b) make it robust and strong (c) increase the secondary voltage (d) reduce energy loss due to eddy current 12. Cathode rays can be deflected by (a) electric field (b) magnetic field (c) both types of fields (d) none of these fields 13. Assertion : No power loss associated with pure capacitor in ac circuit. Reason : No current is flowing in this circuit. (a) Both Assertion and Reason are correct and Reason is the correct explanation of Assertion. (b) Both Assertion and Reason are correct, but Reason is not the correct explanation of Assertion. (c) Assertion is correct but Reason is incorrect. (d) Assertion is incorrect but Reason is correct. 14. Assertion : If a compass needle be kept at magnetic north pole of the earth the compass needle may stay in any direction. Reason : Dip needle will stay vertical at the north pole of earth. (a) Both Assertion and Reason are correct and Reason is the correct explanation of Assertion. (b) Both Assertion and Reason are correct, but Reason is not the correct explanation of Assertion. (c) Assertion is correct but Reason is incorrect. (d) Assertion is incorrect but Reason is correct.
Page 3 Sample Paper 05 CBSE Physics Class 12 15. Assertion (A) : The surface of a conductor is an equipotential surface. Reason (R) : Conductor allows the flow of charge. (a) Both Assertion and Reason are correct and Reason is the correct explanation of Assertion. (b) Both Assertion and Reason are correct, but Reason is not the correct explanation of Assertion. (c) Assertion is correct but Reason is incorrect. (d) Assertion is incorrect but Reason is correct. 16. Assertion : A charge, whether stationary or in motion produces a magnetic field around it. Reason : Moving charges produce only electric field in the surrounding space. (a) Both Assertion and Reason are correct and Reason is the correct explanation of Assertion. (b) Both Assertion and Reason are correct, but Reason is not the correct explanation of Assertion. (c) Assertion is correct but Reason is incorrect. (d) Assertion is incorrect but Reason is correct. SECTION-B 17. Magnetic field lines can be entirely confined with the core of toroid, but not within a straight solenoid, why? 18. A concave lens of refractive index 1.5 is immersed in a medium of refractive index 1.65 what is the nature of the lens? 19. Why are two bulbs lighting the same walls considered as incoherent sources? How do their intensities add up? O When a tiny circular obstacle is placed in the path of light from a distant source, a bright spot is seen at the centre of shadow of the obstacle. Explain. 20. How are infrared waves produced? Why are these referred to as heat waves? Write their one important use. 21. Is the steady electric current the only source of magnetic field? Justify your answer. SECTION-C 22. Distinguish between ‘Intrinsic’ and ‘extrinsic’ semiconductors? 23. A charge Q is given to three capacitors C1, C2 and C3 connected in parallel. Determine the charge on each. 24. How will you explain twinkling of stars? 25. Describe briefly, with the help of a diagram, the role of the two important process involved in the formation of a p n - junction. Continue on n ext page.....