CBSE Class 12 Physics Question Paper 2017 (Set 55/2/3)

CBSE CLASS XII Questions

• 1.

  Write two advantages of reflecting telescope over refracting telescope.
  

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• 2.

  The resistance of a metal wire at \( 20^\circ \text{C} \) is \( 1.05 \, \Omega \) and at \( 100^\circ \text{C} \) is \( 1.38 \, \Omega \). Determine the temperature coefficient of resistivity of this metal.

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• 3.

  An astronomical telescope consists of two converging lenses. One of them of large aperture and large focal length is called objective lens and the other one, of smaller focal length and smaller aperture is called the eyepiece. It is used to see distant objects which are not seen clearly with naked eyes. The image formed by the objective lens acts as an object for the eyepiece and the final image produced by the eyepiece is magnified.
  

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• 4.

  Read the following paragraph and answer the questions that follow.
  In an experiment with convex lens of focal length f, the screen is fixed at a distance D from the object. A student slowly moves the lens away from the object towards the screen and finds that she is able to form sharp image of the object for two positions of the lens. The distance between these two positions of the lens is d.
  

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• 5.

  Read the following paragraph and answer the questions that follow.
  A p-type or n-type semiconductor can be converted into a p-n junction by doping it with suitable impurity. The motion of majority charge carriers causes diffusion current across the junction while the barrier electric field causes motion of minority carriers for drift current. In case of unbiased diode, the diffusion and drift currents are equal. This equilibrium is disturbed by the biasing batteries. Diodes, therefore, allow currents in one direction. This property of diode is used in making rectifiers.
  

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• 6.

  Consider the nuclear reaction \( X \to Y + Z \). Let \( M_x \), \( M_y \), and \( M_z \) be the masses of the three nuclei X, Y, and Z respectively. Then which of the following relations hold true?

  • \( (M_x - M_z)<M_y \)
    
  • \( (M_x - M_y)<M_z \)
    
  • \( M_x>(M_y + M_z) \)
    
  • \( M_x<(M_y + M_z) \)
    
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