Physics Paper 2 Questions and Answers - Kapsabet Mocks 2020/2021

SECTION A: (25 MARKS)
Answer ALL Questions in this section in space provided

1. At what angle should two plane mirrors placed to produce 5 images? (2marks)
2. In a simple cell consisting of copper and zinc plates, bubbles of gas are seen forming around the copper plate
   
   1. What is the name given to this defect (1mark)
   2. Suggest how the defect you have named in 1 (i) above can be minimized (1mark)
3. The diagram shows a 40Ω resistor connected in series to a battery of 6V and negligible internal resistance. Calculate the power dissipated (2marks)
   
4. One way of magnetizing a magnet is hammering. Explain the magnetization is achieved (2marks)
5. Figure 2 below shows a solenoid wound on a soft iron core.
   
   State the polarities at point A and B when the switch is closed (1mark)
6. Figure 3 below shows a display of an a.c signal on a CRO screen.
   
   Determine the frequency given that the time base setting is 200ms per division (2marks)
7. Figure 4 below shows a diagram consisting of a diode, an AC voltage source, a resistor and two cathode ray oscilloscope (CRO1) and (CRO2)
   
   Sketch the voltage through CRO1 and CRO2 (2marks)
   
8. State TWO reasons why Alluminium is preferred to copper in transmission of power ( as overhead cables) (2marks)
9. Define the term ‘wavelength’ of a transverse wave (1mark)
10. A boy standing 400m away from a cliff claps his hands and hears an echo 2.5s later Determine the speed of sound in air (2marks)
11. Velocity of light in water is 2.2×10⁸m/s while in glass velocity is 2.0×10⁸m/s. Calculate the angle of incidence in water which could produce an angle of 30⁰ in glass (2marks)
12. The diagram below shows a point charge close to a flat positive charge. Draw the electric field between them (1mark)
    
13. A virtual image of height 4cm is formed using a convex lens of focal length 20cm. If the size of the object is 1cm, determine the position of object (3marks)
14. Table below shows part of the electromagnetic spectrum
    
    

    Microwave

    Infra-red

    Visible light

    A

    X-ray

    
    Name part labelled A (1mark)

SECTION B (55MARKS)
Answer ALL questions in the space provided

15.  
    1. Figure 7 below shows a positively charged electroscope. A positively charged rod was brought near the cap. Explain the observation (2marks)
       
    2.  
       1. Define capacitance (1mark)
       2. Explain how the capacitance of a parallel plate capacitor can be increased (2marks)
    3. Figure below shows an arrangement of capacitors with effective capacitance of 5μF.
       
    4. Calculate the value of y in Farads. (3marks)
    5. Figure below shows the main features of a cathode ray oscilloscope (CRO).
       
       
       1. Name the parts labelled M& N (2marks)
       2. Explain how electrons are produced in the tube (2marks)
       3. State why the tube is highly evacuated (1mark)
16.  
    1. The figure below shows two straight waves incident on a concave barrier. Complete the diagram above showing how straight waves behave after reflection from a concave barrier (2marks)
       
    2. Figure below shows two loud speakers L1 AND l2 connected to a common signal generator (SG). The two loud speakers L2 and L2 act as coherent sources of sound.
       
       
       
       
       1. What is the meaning of the term coherent source of sound. (1mark)
       2. State and explain the observation made by a person walking along the line AB (2marks)
    3. Figure below shows A wave produced at end and travels towards B.
       
       The wave is reflected by B (barrier) and travels back towards A. The two waves (incident and reflected) superimposed to form a stationary (standing0 wave. On the figure, draw the reflected wave and on it indicate positions of nodes (N) and antinodes (A). (3marks)
17.  
    1. Figure below shows a magnet placed near a coil AB. The coil is connected to a centre 0 galvanometer (G)
       
       
       1. State with a reason the observation made when the magnet is moved away from the coil as shown (3marks)
       2. State what will be observed when the experiment is repeated but with the magnet nearest to the coil end A (1mark)
       3. Explain the change that will be observed if the speed at which the magnet is moved away from the coil is increased (2marks)
    2. A transformer is designed to step down voltage from 240V to 12V. Determine the number of turns in the secondary coil if it has 1200 turns in the primary coil (2marks)
    3. Show that photoelectric effect will not occur if an electromagnet radiation of frequency 7.7×10¹⁴ Hz is incident on a metal surface whose work function is 5.2×10^-19 J (take planks constant =6.63×10^-34JS) (3marks)
18.  
    1.  
       1. Define electric current (1mark)
       2. If a charge of 30μC is made to flow through a conductor in 2 hours what is the current flowing (3marks)
    2. The figure below shows a circuit powered by a battery of e.m.f 5.0 volts with internal resistance r. It also contains load resistances, 10Ω, 12Ω and 24Ω. V is a voltmeter while A1 and A2 are ammeters.
       
       Total amount flowing is 0.25A as shown. Determine
       1. Reading of V (3marks)
       2. Reading of A1 (2marks)
       3. value of r (2marks)
    3. A single room has three bulbs each rated 60W. The bulbs are lit for 10 hours per day. Determine the cost of lighting the bulbs for 30 days (1KWh costs Ksh.3 (2marks)
19.  
    1.  
       1. Draw and name the three types of curved mirrors (3marks)
       2. Use ray diagram on anyone of the mirrors to show what is meant by principal focus (2marks)
    2. The graph below shows values of 1/v and 1/u plotted on a graph in an experiment to determine the focal length of a convex lens.
       
       1. Sketch an experimental set up of apparatus that can be used to obtain data which when plotted will yield similar results (2marks)
       2. From the graph determine the focal length of the lens (3marks)

 Marking Scheme

1. n = ³⁶⁰/_θ−1 √1
   S = ³⁶⁰/_θ -1
   θ = 360/6 = 60⁰√1
2.  
   1. Polarization√1
   2. Add a depolarizer/ an oxidizing agent√1
3. P= V1 = v²/R =36
   P= V1 OR v²/R OR = (6×6)/40 √1
   P= 0.9 W√1
4. Hammering makes the dipoles to vibrate√1
   Earth magnetic field aligns the dipoles√1
5. B- North pole√1
   A- South pole – Allow correct pole at one end
6. Number of divisions =4ms
   Time in milliseconds=4×200=800
   Period (T) = (800×10^-3) s=0.8s√1
   F=1/T = 1/0.8 =1.25HZ√1
7. √1 each
   
8.  
   • It forms a coating at the surface to prevent rusting and as an insulator
   • It is less dense hence easy to carry
   • It is easily available/cheaper (Any TWO √1 each)
9. Distance between a particle in the wave medium and the next one that is in phase with it or Distance between two successive crest/trough √1
10.  
    
11.  
12.  
13.  
14. Ultra-Violet-√1

SECTION B

15.  
    1. There is more divergent √1 +ve charge attracts more electrons (-ve charge) from rod and the leaf. (Reject movement of +ve charges)
       Hence more positive charges created causing more repulsion √1
    2.  
       1. Is charge per potential difference √1
       2.  
          • By decreasing the distance between the plate
          • By increasing the overlapping area of the plates
          • By adding dielectric material between the plates (Any 2)
    3. Parallel = y+4.
       Total capacitance=product/sum√1
       =(y+4)10/(y=4)+10=5μF√1
       40+10y=20+5y+50
       5y=70-40=30
       Y=6μF√1
    4.  
       1. M is cathode√1
          N is anode√1
       2. When the current flows, the filament gets heated √1
          This causes electrons to be ejected/ removed from the cathode√1
       3. To prevent electrons from colliding and ionizing the air molecules inside √1
16.  
    1. √1
       
    2.  
       1. Source producing sound waves of same frequency wavelength (hence speed) and same or nearly same amplitude √1
       2. Alternate loud and soft sound√1
          At loud sound, waves from L1 and L2 arrive in phase leading to constructive interference.
          At soft/quite sound waves from L1 and L2 arrives out of phase leading to destructive interference. √1
    3. √2
       
17.  
    1.  
       1. Galvanometer deflects from zero to maximum them back to zero√1
          There is a charging magnet linkage through which induce an emf in the coil√1
          The indirect emf will cause an induced current to flow√1
       2. The galvanometer deflection will be in the opposite√1
       3. A higher deflection will result√1 since the rate of change of magnetic flux linkage will be higher√1
    2. Ns/Np = Vs/Vp or Ns/1200 = 12/240 √1
       Ns =60 turns√1
    3. E=hf√1
       6.63×10^-34×7.7 ×10¹⁴ = 5.1051×10^-19J√1
       (5.1051<5.2) × 10^-19 J√1
       
       Hence photoelectric emission will not occur
       
       Accept energy of radiation is less than work function of the metal surface√1
18.  
    1.  
       1. Current is charge per unit time √1
          
          
          
19.