PHYSICS PAPER 2 - FORM 4 END TERM 1 EXAMS 2020

SECTION A: 25 marks

Answer all questions in this section in the spaces provided.

1. Figure 1 below shows reflected rays from a plane mirror.
   
   Fig. 1
   By ray construction, show the position of the image and the object. (1 mark)
2. Figure 2 represents an object O and the image I formed by a concave mirror.
   
   Fig. 2
   By suitable rays, determine the focal length of the mirror. (2 marks)
3. Two leaders A and B are rated as shown on the table below
   

   	Heater A	Heater B
   Resistance, ohms	RA	RB
   Power, watts	W	3W
   Voltage, volts	N	¼

   Determine the ratio R_A: R_B (3 marks)

4. The figure below shows the path of light through a transparent material placed in air.
   
   Fig. 3
   Calculate the refractive index of the transparent material. (3 marks)
5. Figure 4 below shows a highly charged needle bought near a candle flame
   
   Explain why the flame burns in the direction shown (2 marks)
6. Explain with an aid of a diagram why to a diver under water, most of the surface looks slivery. Bubbles of air rising from the diver look slivery. (2 marks)
7. Explain why soft iron keepers are suitable for storing magnets. (2 marks)
8. State two quantities that are used to determine whether accumulator require recharging or not. (2 marks)
9. Figure 5 below shows arrangement of three capacities of 10µF, 2µF and 5µF.
   
   Fig. 5
   Determine the effective capacitance. (3 marks)
10. Sketch the magnetic field for a conductor shown in the figure below. (2 marks)
    
    Fig. 6
11. In a pin - hole camera, what is the effect of making the pin - hole small but square in shape?(1 mark)
12. An electric heater is rated 3KW what is the electrical energy in kWh (Kilo watt-hours) consumed by the heater when used on a 240V supply for 180 minutes? (1 mark)
13. Briefly explain why in domestic wiring all the lamps in the house are connected in parallel (1 mark)

SECTION B: 55 marks

Answer all questions in this section.

14.  
    1. In an experiment with capacitor the charge stored was measured for different values of charging potential difference and the following results were obtained.
       

       Charge stored (µC)	7.5	30	60	75	90
       Potential difference(V)	1.0	4.0	8.0	10.0	12.0

       1. Plot a graph of charge stored (y-axis) against potential difference on the grid provided. (4 marks)
       2. Use the graph to determine the capacitance of the capacitor. (2 marks)
    2. Resistors of 2Ω and 3 Ω are connected in series with a cell and voltmeter connected across the 3 Ω resistor reads 1V, but this increases to 1.2V when an extra 2Ω resistor is connected in parallel with the first 2 Ω resistor, calculate the e.m.f and the internal resistance of the cell. (4 marks)

15. The following data was collected to find the focal length of a convex lens.
    

    Image distance, v	13.3	15.0	16.7	20.0	30.0
    Magnification, M	0.3	0.5	0.7	1.0	2.0

    1. Plot a graph of M against V (5marks)
    2. Use your graph to find the focal length of the lens (3 marks)
    3. Find the power of the lens (2 marks)
    4. State 4 similarities between the eye and the lens camera (4 marks)
    5. What is long sightedness? (1 mark)

16.  
    1. State two differences between sound waves and electromagnetic waves (2 marks)
    2. Figure below shows a waveform of a wave moving at velocity of 2m/s.
       
       Fig. 7
       Determine:
       1. The periodic time (T) (2 marks)
       2. The wavelength (2) (3 marks)
    3. A fathometer produces sound in a ship and receives two echoes where there is a raised sea bed one after 2.5 seconds and the other after 3.0 seconds. Find the height of the raised sea bank if the velocity of sound in water is 1460m/s. (3 marks)
17. A 10 uf capacitor is charged to a potential difference of 300V and isolated. It is then connected in parallel to a 5 uF capacitor.
    1. Find the resultant potential difference. (3 marks)
    2. The energy stored before connection. (3 marks)
    3. The energy in the two capacitors after connection. (3 marks)
18.  
    1. State any one properties of magnetic flux lines. (1 mark)
    2. A model railway truck has a magnet attached to it as shown in fig 6 below, not to scale. It is free to run on rails from a higher level A to a lower level B. At B, a thick loop of copper wire is placed horizontally across the track so that the magnet straddles the wire when the truck is at B. A large electric current passes through the wire, which is connected to a battery. The truck is released from A and it rebounds without physical contact when reaching B. (2 marks)
       1. Explain why the truck rebounds in this manner. (2 marks)
       2. Describe its subsequent motion. (2 marks)
       3. What would be the effect of increasing the current through the wire, Explain (2 marks)
       4. What would be the effect of increasing the load in the truck? Explain (2 marks)
       5. What would be the effect of reversing the holes of the magnet? Explain. (2 marks)

MARKING SCHEME

1.  
   
   Mark for construction for incident rays using laws of reflection then virtual rays to show position of the image
2.  
   
   Draw a ray parallel to the principal axis-reflected through the principal focus F. Measure the distance between the mirror and for the principal ray to determine C and radius of curvature r, focal length= ^r/₂
3.  
   
4.   
   
5. Charges concentrated by point action;
   Similar charges from ionized gas repel while unlike charges attract;
6.  
   
   At O there is total internal reflection because the angle of incidence is greater than the critical angle of water air.
7. Magnetism is easily induced in them. The dipoles of the Keepers form a closed loop with those in the magnets hence protecting the magnets from being demagnetized
8. - Relative density of the acid;
   - The voltage output

9.  
   
10.  
    
11. The image remains unaffected√ by the change from a small circular hole to a small square hole
12. 3 kWh × 3 hrs
    9 kWh√
13. So that the p.d across them is the same√ accept this reduces resistance
14. 
    
    (b)
    
15.  
    1. Graph
       scale 1 mark
       Axes                1 mark
       Plotting            2 marks
       Line                 1 mark
       
       
       d)
       

       Eye	Camera
       -          Choroid layer black -          Image forms on retina -          Iris controls light entering -          Has a crystalline convex lens	-          Camera box painted black -          Image forms on photo film -          Diaphragm controls light entering -          Has a convex lens

       e) Long sight is a defect where the eye cannot see distant objects clearly but near one’s only. (lens has long f or eyeball too short
16.  
    
    1.  
       

       Sound waves	Electromagnetic waves
       -          Longitudinal -          require material medium -          Have compressions and rarefactions -          Particles moves parallel to wave motion	-          Transverse -          Do not require material medium -          They have crests and troughs -          Particles moves perpendicularly to the wave motion

    2.  
       
    3.  
       

17.  
    
18.  
    1. - They never cross
       - Are continuous
       - Are under tension
    2.  
       1. The current flowing through the copper loop produces a magnetic force that repels the magnet attached to the truck hence rebounds
       2. It moves to and fro then comes to a halt some distance away from the coil
       3. Truck rebounds more because a stronger repulsive force will be produced
       4. If may not rebound, it will require a stronger repulsive force
       5. It does not rebound the force due to direct current is now attractive