PHYSICS PAPER 2 - KCSE 2019 NYANDARUA PRE MOCK EXAMINATION

SECTION A: (25 MARKS)
Answer ALL questions this section in the spaces provided.

1. What property of light is suggested by the formation of shadows?                     (1mark)

2. Why are audio recording hall walls covered with soft materials.                         (1mark)

3. A highly negatively charged rod is gradually brought close to the cap of a positively charged electroscope.  It is observed that the leaf collapses initially and then diverges.  Explain this observation.                                                                                 (3marks)

4. The figure below shows a ray of light incident on a face of semicircular prism. 
   
   Determine the refractive index of the glass prism.                             (3marks) 

5. Explain why repulsion is the only sure test for polarity of a magnet.                   (1mark)

6. State the use of manganese (IV) oxide in a dry cell.                                            (1mark)

7. A lamp of height 6cm stands infront of pin-hole camera at a distance of 24cm from the pin-hole. The camera screen is 8cm from the pinhole.  Calculate the height of the image formed on the screen.                                                                                        (3marks)

8. A car accumulator is rated 40Al and is expected to supply a constant current for 120 minutes.  Calculate the amount of current delivered.                                            (2marks)

9. The figure below shows two incident rays on a concave mirror from the top of an object. 
   
   Complete the ray diagram showing the reflected rays.                                        (2marks)   

10. An electric bulb rated 40W is operated on240V mains.  Determine the resistance of its filament.                                                                                                               (3marks)
11. The force on a straight conductor carrying current in a magnetic field can be varied by changing, among others, the magnitude of the current and the magnetic field strength.  Name the other factors that can be changed to vary the force.                               (2marks)

12.  
    1. Distinguish between transverse and longitudinal waves.                               (1mark)
    2. Give one example of a transverse wave and one example of a longitudinal wave.  (2marks)

SECTION B: (55 MARKS)
Answer ALL questions this section in the spaces provided.

13.  
    1. In an experiment to determine the internal resistance of a cell, the following circuit was used.
       
       It was noted that when S is open, the voltmeter reads 1.5V and when S is closed the voltmeter reads 1.3V and ammeter reads 0.2A.
       1. What is the e.m.f of the cell.                                                                                 (1mark)
       2. Determine the lost voltage.                                                                                   (1mark)
       3. Find the value of R.                                                                                              (2marks)
       4. Find the internal resistance of the cell.                                                                 (2marks)
    2. Study the circuit below and answer the questions that follow.
       
       
       1. Determine the effective resistance of the circuit.                                           (2marks)
       2. Find the ammeter reading.                                                                              (2marks)
       3. Find the p.d between X and Y.                                                                      (2marks)
       4. State the factors that affect the resistance of a conductor.                            (3marks)

14.  
    1. The diagram below represents a wave motion.
       
       
       1. What is the amplitude of the wave in metres.         (1mark)
       2. How many cycles are made.                                                                           (1mark)
       3. Calculate the wavelength, l, of the wave.                                                     (2marks)
       4. Calculate the frequency of the wave.                                                             (2marks)
       5. Calculate the velocity of the wave.                                                                (2marks)
    2.  
       1. The echo sounder of a ship receives the reflected wave from a sea-bed after 0.2 seconds.  What is the depth of the sea bed if the velocity of sound in water is 1450m (3marks)
       2. State two factors that affect the speed of sound in air.                                 (2marks)

15.  
    1. State two conditions necessary for total internal reflection to occur.                        (2marks)
    2. Define the term critical angle as used in refraction of light.                           (1mark)
    3. The figure below shows the path of a ray of light through a glass prism.  The speed of yellow light in the prism is 1.88 × 10⁸m/s. 
                                                  
    4.  
       1. Determine the refractive index of the prism material for the light (speed of light in vacuum, c = 3.0 × 10⁸m/s.       (3marks)
       2. Show on the figure, the critical angle, c, and determine its value.                       (4marks)
       3. Given that r = 21.2º, determine the angle q.                                                   (3marks)

16.  
    1. State the advantages of using a convex mirror as a driving mirror.                (2marks)
    2. The figure below shows an object O placed infront of a converging mirror of local length 15cm.
       
       Draw on the figure a ray diagram to locate the image formed.                            (3marks)
    3. State why parabolic reflection is used in car headlights. 

17.  
    1. State three factors that affect the strength of an electromagnet.                   (3marks)
    2. In the set up below, the suspended metre rule is in equilibrium balanced by the magnet and the weight shown.  The iron core is fixed to the bench:
       
       
       1. State and explain the effect on the metre rule when the switch S, is closed.       (2marks)
       2. What would be the effect of reversing the battery terminals?                             (1mark)
    3. The figure below shows two parallel current carrying conductors A and B placed close to each other.  The direction of the current is into the plane of the paper. 
       
       On the same figure.
       1. Sketch the magnetic field pattern.                                                                  (1mark)
       2. Indicate the force F due to the current on each conductor.                           (1mark)

MARKING SCHEME

SECTION A

1. Light travels in a straight line. Pj
2. Soft materials are good absorbers of sound; to minimize undesirable echo effects. Pj
3. As the rod approaches the cap, the negative charges on the cap are repelled towards the rod. Pj The leaf collapses since the positive charges on it are neutralized by the negative charge. Pj As the rod gets close to the cap, more negative charges are repelled to the leaf, causing it to diverge. Pj
4.  
   

5. Attraction occurs between unlike poles of a magnet and can also occur between a magnet and unmagnetised magnetic material. Pj
6. To act as a depolarizer.           Pj
7.  
   
9. - The reflected rays  Pj
   Must emerge parallel
   - Direction of rays  Pj

10.  
     
    
    
11. - Length of the conductor in the field. Pj
    - The angle the conductor makes with the field. Pj
    

    12.	(i)	Transverse	Longitudinal
    	(ii)	- Recognized by crests and troughs  Pj - Particles in transmitting medium    vibrate at right angles. - Light waves  Pj - Water waves	- Recognized by compression and rare    factions. - Particles in transmitting medium   vibrate in the direction of wave motion. Sound waves  Pj

SECTION B:

13.  
    1.  
       1. 1.5V
       2. 1.5 – 1.3 = 0.2V  Pj
       3. V = IR
          1.3 = 0.2R  Pj R = 6.5W  Pj
    2.  
       1. Ir = 0.2
          0.2r = 0.2  Pj
          r = 1W  Pj
       2. R_T = 1.5 + 2.5 = 4W  Pj
       3. V = IR  P
          2 = 4I  Pj      I = 0.5A  Pj
       4. V = IR
          = 0.5 ´ 2.5  Pj = 1.25V  Pj
       5. - Length of the conductor  Pj
          - Temperature  Pj
          - Cross-section area of the conductor. Pj

14.  
    1. 0.04m  Pj
    2. 3½ cycles  Pj
    3. Pj = 2cm  Pj
    4. T = 0.2sec       
       f  = 5HZ  
    5. V  =  fl
       = 0.1m/s 
    6. = 1450 ´ ½ ´
       0.2= 145m  Pj
    7. - Direction of winds  
       - Humidity                       Any two
       - Temperature  

15.  
    1. - A ray of light must be traveling from a denser medium to less dense medium. Pj
       - Angle of incidence in the denser medium must be greater than the critical angle between the two media. Pj
    2. Angle of incidence in the denser medium for which angle of refraction (r) in less dense medium is 90º. Pj
    3.  
       

16.  
    1. - Always forms up-right images Pj
       - Have wide field of view Pj
       
    2.  
       1. - The two rays of light PPj j
          - Location of the image Pj
       2. Parabolic reflectors bring into focus all parallel rays to the principal
          focus thus producing parallel beams of light of high intensity. Pj

17.  
    1. - Amount of current. Pj
       - Number of turns in a coil Pj
       - Shape of the core Pj
    2.  
       1. The magnet will be attracted Pj towards the soft iron core. 
          The end of the coil facing the magnet becomes South Pole when switch is closed. Pj
       2. The polarities of the electro-magnet becomes reversed therefore the magnet is now repelled away from iron core. Pj
    3. - Field Pj
       - Attractive forces Pj