PHYSICS PAPER 2 Marking Scheme - 2017 KITUI MOCK EXAMINATION

Marking Scheme

SECTION A

2.  
   • Enlarged hole allows more light to reach the screen ü½
   • Enlarged hole allows multiple images to beü½ formed on the screen hence overlapping images

3.  
   1. 5V
   2. 6V
4.  
   

5.  
   1. a = 0
      b = 0
   2. Energy
6.  
   

7.  
   • lamps in parallel produce light of the same brightness
   • When lamps are in parallel, failure in one does not affect others

8. When the switch is closed, x-rays ionize the air particles between the plates, where the positive ions move to the negative plate, while negative ions move to positive plate, completing the circuit hence a deflection is seen on the milliameter 
   
9. This is because of most of the energy of the electrons that strikes the anode is converted into heat which causes the heating of the anode. 
   
10.  
    

11. V = 330ms^-1
    f = 0.44 kHz                                 
    1kHz = 1000Hz
     f = (0.44 x 1000)Hz = 440Hz
    λ=^v/_f=³³⁰/₄₄₀
    =0.75m
12.  
    

13. P = ¹/_f(m) , f = 40cm = 0.40m
    =¹/_0.40= +2.5D

SECTION B

14.  
    1. The electroscope discharges through the electrons flowing through your body to the ground.
       
    2.  
       
    3.  
       

15.  
    1.  
       1. Electrons are produced through thermionic emission due to heat energy 
          
       2. Detected through the glowing of the fluorescent screen
       3.  
          1. Variable p.d in the grid – controls the amount of electrons reaching the screen
             
          2. Variable p.d in the anodes – ensures we have electrons of varying strength               
    2.  
       1. Time base setting 20 ms/cm
          λ= 2cm
          T = Time base setting × No. of division for one oscillation
          = 20ms/cm × 2cm = 40 ms = ⁴⁰/₁₀₀₀s= 0.04s
          
       2. f= ¹/_T=¹/_0.04=¹⁰⁰/₄=25 Hz
16.  
    1. I=0.02A
       t=1s
       e=1.6 × 10^-19C
       Number of electrons n?
       Q=eη
       but Q = It
       therefore eη = It
       η=^It/_e
       η=^{0.02 × 1}/_{1.6 × 10^-19}
       =1.25 × 10¹⁷ electrons
    2.  
       
    3.  
       
17.  
    1.  r = 15^o
       
    2.  
       1. θ₁ = 20^o
          
       2. θ₂ = 70^o 
    3.  
       1. Use of thick cables
       2. Transmit power at high voltage to reduce or the current of transmission. Power loss α I²
          
    4.  
       
18.  
    1.  
       1. The pointer of the galvanometer deflects to one side and then back to zero 
          
       2. It deflects to the opposite side and back again to zero 
          
    2.  
       1. Amount of voltage in the circuit when the switch is opened 
    3.  
       1. R=^V/_I= ^2.2/_0.4= 5.5 Ω
       2.  Non – ohmic – graph is a curve not a straight line ü¹
    4.