Sunday 6 May 2018

SCHOOL BASED ASSESMENT EXAM A PAPER 2


Name:………………………………………………………………………..        Index No.: ………

School:………………………………………………………………………         Sign.: …………

                                                                                                        Date:……………………
Kenya Certificate of Secondary Education ( K.C.S.E )
232/2
PHYSICS
PAPER 2
(THEORY)
JULY/AUGUST
TIME: 2 HOURS
                 
SCHOOL BASED ASSESSMENT EXAM A PAPER 2

FORM 4
PHYSICS
PAPER 2

INSTRUCTIONS TO CANDIDATES:
·         Write your name, admission number and the name of your school in spaces
·         Sign and write the date of examination in the spaces provided above.
·         This paper consists of sections: A and B.
·         Answer all the questions in section A and B in the spaces provided below each question.
·         All working must be clearly shown where necessary.
·         Mathematics tables and silent electronic calculators may be used.

FOR EXAMINER’S USE ONLY
SECTION
QUESTION
MAXIMUM SCORE
CANDIDATE’S SCORE
A
1 – 13
25



B
14
09

15
10

16
09

17
10

18
09

19
08

                              TOTAL SCORE
80



This paper consists of 8 printed pages.
Candidates should check to ascertain that all pages are printed as indicated
and that no questions are missing.
SECTION A (25 MARKS)
Answer ALL questions in this section in the spaced provided.
1.   Convex mirrors are used in cars as driving mirrors because they have a wide field of view.
Sketch a labelled diagram to show the wide field of view.                                           (2marks)






2.   Cathode ray oscilloscope (CRO) is more accurate voltmeter that moving coil voltmeter.  Give two reasons in support to this statement.                                                                       (2marks)
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3.   Differentiate between electromotive force and potential difference.                            (2marks)
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4.   Arrange the following electromagnetic waves in the order of increasing wavelength.
Ultraviolet, x – rays, radiowaves, g – rays.                                                                     (1mark)
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5.   Distinguish between thermionic and photo-electric emission.                                        (1mark)
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6.   Bulb x lights while bulb y does not.  Explain.                                                               (2marks) 
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7.   The figure below shows a ray of light traveling through water, whose refractive index is 1.33 and glass.
 



Determine the refractive index of glass.                                                                        (3marks)




8.   The figure shows an object O in front of a curved mirror M, on the same figure, locate the image.                                                                                             (3marks)                                                                                                                                                           
 


9.   Determine the total capacitance of the arrangement below.                                           (1mark)


 


10. Indicate the poles of the electromagnet shown in the figure below.                               (1mark)

 


11. What is meant by threshold frequency as used in photoelectricity.                                (1mark)
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12. Give the difference between real and virtual image.                                                     (2marks)
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13. The following is part of a radioactive decay series.
Determine the values of a and b.                                                                                   (2marks)
                                                                                                                                                                                
                                               
                             ß                           ɑ
 


14. Figure 3 below shows a transverse wave traveling along x-axis.


Determine from the graph in figure 3 above:-
i)  The wavelength of the wave.                                                                                    (1mark)


ii)  The amplitude of the wave.                                                                                      (1mark)



SECTION B: (55 MARKS)
Answer all questions in this section in the space provided.
15. a)  State Ohm’s Law.                                                                                                       (1mark)
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b)  A wire was connected to a battery and it was found that the energy converted to heat was 30J when 20C of charge flowed through the wire in 5 seconds.  Calculate:-
i)  The p.d between the ends of the wire.                                                           (2marks)




ii)  The current flowing through the wire.                                                         (2marks)




iii)  The resistance of the wire.                                                                       (2marks)




iv)  The average power development in the wire.                                             (2marks)






c)   The graph shows results obtained in an experiment to determine the e.m.f (E) and the internal resistance , r, of a cell.
 


            Given that the equation of the graph is .
            Use the graph to determine the values of:-
                        i)  E                                                                                                                    (2marks)





                        ii)  r                                                                                                                   (3marks)







16. a)  State one cause of energy losses in a transformer and explain how it can be minimized.(2marks)
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b)  A transformer is designed to supply a current of 7.5A at potential difference of 100V to a motor from       an a.c supply of 240V.  If the efficiency of the transformer is 85%.
      Calculate:-
                  i)  The power supplied to the transformer.                                                         (2marks)






                  ii)  The current in the primary coil                                                                     (2marks)






c)        The figure shows a cross-section of a bicycle dynamo.  The wheel is connected by an axle to a permanent cylindrical magnet and is rotated by the bicycle tyre.
 


i)  Explain why the bulb lights.                                                                                       (1mark)
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ii)  How can the bulb be made brighter?                                                                        (1mark)
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17. a)  The figure below shows a bridge rectifier.
 


      i)  Define the term rectification.                                                                                      (1mark)
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      ii)  Describe how the illustrated rectifier works (2marks)
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      iii)  What modifications can we make on the arrangement to improve the quality of the output                                                                                                                                                                 (1mark)
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     iv)   Sketch on the areas below how the improved output is displayed on a C.R.O screen.  (1mark)



b)   The figure below shows an expansion cloud chamber.

 


i)  What is the purpose of the Vapour?                                                                  (1mark)
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ii)  Explain how the radiations emitted by the radioactive source in the chamber are detected.                                                                                                         (2marks)
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18. a)  The diagram below shows part of x-rays tube.
 

      Name parts:-                                                                                                                   (2marks)
                  P  ........................................................................
                  Q  .......................................................................
b)  i)  What is the effect on the wavelength of x-rays if the number of electrons hitting metal target are increased.                                                                                                             (1mark)
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      ii)  What is the effect on wavelength of x-rays when p.d across the tube is decreased  (1mark)
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c)   Calculate the maximum velocity of electrons that would produce x –rays of frequency 8.0 x 108Hz if only 20% of kinetic energy is converted to x-rays.  (Take planks constant = 6.63 x 10-35Js).   (2marks)







d)   An x-ray tube operating at a potential difference of 50kV has a tube current of 20mA.  Calculate:-
i)  The electric power input.                                                                                                   (2marks)




ii)  The number of electrons hitting the target per second.                                                    (2marks)



iii)  The velocity of the electrons when they hit the target.                                                    (3marks)



19. I.  The figure below shows how a near object O is focuses in a defective eye,




a)  What problem does the observer face when viewing an object at the near point.        (1mark)
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b)  i)  Sketch on the same figure how a distant object is focused by the eye.                     (2marks)
      ii)  State the nature of the defect.                                                                                    (1mark)
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c)   i)  A pastor is known to have the defect stated in (b) (ii)  above how will the pastor handle a bible as he read it.                                                                                                            (1mark)
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ii)  How would you advise the pastor as he goes about correcting the defect.               (1mark)
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II.        a) 

 

 Show on the diagram the path of the incident ray after striking AB of glass prism whose refractive index is 1.5 through the prism.                                                        (4marks)
  b)  Give two advantages of using optical fibres instead of copper wires in transmission of messages.                                                                                                              (2marks)
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