CBSE Physics Model Practice Question Paper- 7
1. In a Young’s double slit experiment the intensity of bright fringe is I. If the slits have the same width what is intensity due to one slit only?
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2. Which temperature is higher in the graphs?
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3. Two large conducting plates are arranged parallel to each other. One of the plates is given a charge + Q. What are the charges induced on the surfaces of other plates?
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4. Give the name of the source and the spectral range of the following wavelengths of the electromagnetic spectron: 5800 A, 200 m, 0.6 A and 1200 A.
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5. Write the truth table for the combination of the gates.
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6. An electron is moving vertically downwards. If it passes through a magnetic field which is directed from south to north in a horizontal plane then in which direction the electron would be deflected?
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7. When the switch S in turned off which bulb will die out promptly?
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8. A lens of focal length/forms the image of a luminous object on a screen. The image is n times enlarged. What is the distance of the screen from the lens?
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9. Draw approximate equipotentials for a negatively charged metallic sphere.
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10. Under which’ of the following two cases more work has to be done in moving further apart the plates of a charged capacitor and why?
(i) the charging battery remains connected to the capacitor.
(ii) after charging the capacitor the battery is removed.
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11. Describe an experiment to verify the second law of electrolysis.
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12. Draw lines of force for a bar magnet placed in a horizontal plane with its axis in the magnetic meridian N →N.
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13- The magnetic field B at the centre of a ring with current 11 A is found to be 120 x 4π x 10-7 T. Find the diameter of the ring.
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14. Can the primary and secondary of a transformer be interchanged to connect it from a step up to a step down transformer and vice versa? Why?
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15. Explain two different methods with necessary electrical connections to light up a 100 W, 15 volt bulb by a 220 V - 50 Hz a.c. source. In which of the two methods more energy is dissipated and why?
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16. Light of wavelength 2000 A falls on an aluminium surface. In aluminium 4.2 eV are required to remove an electron. What is the K.E. of (a) the fastest electron (b) the slowest electron © what is the stopping potential? (d) What is the cut-off wavelength?
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17. Distinguish between natural and artificial radioactivity. Find an expression for activity at time I in terms of half life of a radioactive substance.
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18. Draw an energy band diagram for sodium chloride.
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19. The capacitors shown are of equal capacitances joined in series with a battery of 10 V. The point B is earthed. Find the potential of A and C.
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20. Determine (i) the potential of A (ii) the potential of/). (iii) reading of the voltmeter connected across 16 V battery,
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21. Distinguish between See back effect and Joule effect. A150 Ω electric heater can carry a maximum current of 1.1 A. It is to be operated on a 220 V line, what is the minimum resistance required in the circuit?
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22. Two alternating emfs of peak values 8 V and 6 V and frequencies 50 Hz and 100 Hz respectively are fed in a circuit containing a resistance of 7.07 Ω. What is the rms current in the circuit?
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23. A thin sheet of glass (µ- 1.5) of 6 |om thickness is interposed in one of the beams of the Young’s double slit experiment. This results in the shifting of the zeroth fringe to theposition occupied by the fifth fringe. What wavelength of light is used?
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24. For what value of wavelength of light our eye is most sensitive? What is the value in lumen/watt corresponding to this wavelength? Explain with the use of a graph.
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25. Define luminuous intensity of a light source and illuminance of a surface. How does the intensity of illuminance of a surface depend upon its distance from a light source? Explain.
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26. State the three factors on which the focal length of a lens depends. The distance between an object and a screen is d. A convex lens of focal length /is placed between the object and the screen. What should be the minimum value of d so as to obtain the image of the object on the screen.
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27. How can the surface temperature of earth be found theoretically from Stefan Boltzmann law?
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28. A particle of charge q and mass m moves along a circle of radius r under the action of a magnetic field B. An electric field is suddenly switched on and it is observed that the particle begins to move with a uniform velocity along the tangent to the circle. Find the magnitude and the direction of the electric field.
Explain with the help of a suitable diagram the net torque acting on a rectangular loop carrying a current and placed in a magnetic field.
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29. Explain critical mass and controlled chain reaction in reference to a nuclear reactor clearly indicating in a diagram (i) the moderator (ii) coolant (Hi) control rods.
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30. What are the methods of finding Plank’s constant h? State how work function of the cathode can be determined from the photoelectric effect?
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