Physics Paper 2 Questions and Answers - Nyeri Mocks 2021 Exams

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Instructions to candidates

  • This paper has two sections, A and B
  • Answer all questions in Section A and Section B in the spaces provided.
  • All work must clearly be shown.
  • Mathematical tables and non-programmable calculators may be used.

SECTION A (25 MARKS)

  1. Figure 1 shows two plane mirrors AB and BC inclined at an angle of 100° . A ray of light is incident on mirror AB at an angle50°. Complete the diagram to show the path of the ray on reflection from mirror BC. 3mks
    NM2021 Phys PP2 ET2 Q1
  2. The chart below shows an arrangement of different parts of the electromagnetic spectrum.
     Radio wave   A   B   Visible light   C   D   E 
    1. Name the radiation represented by A. (1mk)
    2. Name one detector of radiation C (1mk)
  3. A lady holds a large concave mirror of focal length 1m, 80cm from her face. State one characteristic of her image in the mirror. (1mk)
  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)
    NM2021 Phys PP2 ET2 Q4
  5. An electric bulb rated 40W is operated on 240V mains. Determine the resistance of its filament. (3marks)
  6. The diagram below shows a conductor in a magnetic field.
    NM2021 Phys PP2 ET2 Q6
    Indicate on the diagram the direction of motion. (1mark)
  7. Figure 5 below shows a simple transformer connected to a 12v a.c source and an a.c voltmeter.
    NM2021 Phys PP2 ET2 Q7
    Determine the reading on the voltmeter. (2 marks)
    The number of turns in primary cell is 10while in the secondary it is 5.
  8. It is observed that when a charged body is brought near the cup of a positively charged electroscope, the divergence of the leaf increases. State the type of charge on the body(1mark)
  9. Waves pass from deep water to shallow water and refraction occurs.
    NM2021 Phys PP2 ET2 Q9
    Calculate the speed of the waves after refraction occurs (2 marks)
  10. An echo sounder of a ship transmits sound waves to the depth of the sea and receives the echo after 2.4 seconds. If the speed of sound in water is 1600ms−1 , determine the depth of the sea. (3 marks)
  11. The diagram in the figure 5.0 below shows an object O placed in front of a converging lens.
    NM2021 Phys PP2 ET2 Q11
    Using ray diagram determine the position of the image. (3 marks)

SECTION B( 55MARKS)

  1.  
    1. In an experiment to determine the internal resistance of a cell, the following circuit was used.
       NM2021 Phys PP2 ET2 Q12
      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.
          NM2021 Phys PP1 ET2 Q16d
      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)
  2.  
    1. The image formed by a convex lens is erect. On Figure 10 below, draw the object andusing ray diagram, locate and draw the erect image. (3mks)
      NM2021 Phys PP2 ET2 Q13 
                                     Figure 10
    2. Apart from being erect, state two other characteristics of the image. (2mks)
    3. In an experiment to determine the focal length of a converging lens using lens formula, several values of image distance corresponding to value of objectdistanceU were determined and a graph of magnification m against image distance v,plotted as shown in Figure 11 below
      NM2021 Phys PP2 ET2 Q13c
      The equation of the graph can be represented by the equation
      m= v/f âˆ’ 1
      1. What does the gradient of the graph represent? (1mk)
      2. Determine the focal length of the lens. (2mks)
      3. Find the value of object distance for which the image is not magnified. (1mk)
      4. An object of height 10.5cm stands before a diverging lens of focal length 20cm and a distance of 10cm from the lens. Determine the image distance. (2 mks)
  3.  
    1. The refractive index of glass is 3/2 and that of water is 4/3 . Calculate the refractive index of glass with respect to water. (2 mks)
    2. The figure below shows a ray of light incident at an angle of 35.6° at point D on the first face of a glass prism ABC. The refractive index of the prism is 1.6.
      NM2021 Phys PP2 ET2 Q14b
      1. Determine the angle of refraction at point D. (2 mks)
      2. Find the angle of incidence of the refracted ray on the face AC to 1 decimal point. (2 mks)
      3. Complete the ray diagram to show the emergent ray from the face AC. (2 mks)
      4. State two conditions necessary for total internal reflection to occur. (2 mks)
  4.  
    1. A student stands some distance from a high wall and claps his hands
      1. What two measurements would need to be made in order to determine the speed of sound? (2mks)
      2. Describe how you would make use of these measurements (2mks)
      3. The speed of sound in air is 330m/s. How far from the wall would you stand? Choose an answer from the following distances 10m, 200m, 500m. Give reasons why you did not choose each of the other two distance.(2mks)
    2. The balloon filled with carbon dioxide can act like a lens and focus sound from a loud speaker. On to the microphone, Figure 6 show waves produced by loud speaker moving toward the balloon.
      NM2021 Phys PP2 ET2 Q15b
      1.  Complete the diagram to show what happens to the sound waves when they have passed through the balloon and moves towards the microphone. (2mks)
      2. The loud speaker is now moved toward the balloon. This results in less sound at the microphone. Explain why there is less sound at the microphone (1mk)
      3. The frequency of the sound emitted by the loud speaker is 1020Hz. Calculate the wavelength of the sound wave in air where its velocity is 340m/s (2mks)
  5.  
    1. Figure 9 below shows two circuits close to each other.
      NM2021 Phys PP2 ET2 Q16a
                                          Fig 9
      When the switch is closed, the galvanometer shows a reading and then returns to zero. When the switch is then opened, the galvanometer shows a reading in the opposite direction and then returns to zero. Explain these observations. (2 Marks)
    2. Explain how energy losses in a transformer are reduced by having:
      1. A soft-iron core. (2 Marks)
      2. A laminated core (2 Marks)
    3. An ideal transformer has 2000 turns in the primary circuit and 200 turns in the secondary circuit. When primary circuit is connected to a 400V a.c. source the power delivered to a resistor in the secondary circuit is found to be 800W.
      Determine the current in
      1. The secondary circuit(3 Marks)
      2. The primary circuit (3 Marks)

MARKING SCHEME

SECTION A

  1.  
    NM2021 Phys PP2 ET2 ans1
  2.  
    1. microwave
    2. Photographic film, photocell, fluorescent material.
  3. magnified / erect / virtual
  4. n =   1     âœ“
         sin c
       =   1      âœ“ = 1.4945 âœ“
         sin 42
  5. P = V2  âœ“
          R
    = (240)2 = 144.0 Ω âœ“
          40
  6.  
    NM2021 Phys PP2 ET2 ans6
  7. Ns  =  Vs
    Np      Vp 
     5  = Vs âœ“ Vs = 5 Ã— 12 = 6V  âœ“
    10    12               10
  8. Positive
  9. f = v/λ (same frequency)
    V1 = V2
    λ1     Î»2
    2 = V2 âœ“ => V2 = 2 x 0.4 = 0.8 m/s âœ“
    1    0.4
  10. 2d = v + t âœ“
    2d = 1600 x 2.4
    d = 1600 x 2.4 ✓ = 920m âœ“
                  2
  11.  
    NM2021 Phys PP2 ET2 ans11

SECTION B (55 MARKS)

  1.  
    1.  
      1. 1.5v âœ“
      2. 1.5 âˆ’ 1.3 = 0.2v âœ“
      3. V = IR
        1.3 = 0.2R âœ“
        R = 1.3 = 6.5Ω âœ“
               0.2
      4. E = 1 (R + r)
        1.5 = 0.2 (6.5 + r) âœ“
        1.5 = 1. 3 + 0.2r
        0.2r = 0.2
        R = 1 Ω
    2.  
      1. = + + 1  
        R  R1   R2   R3
             =1/6 + 1/3 + 1/6 = 1 + 2 + 1 = 4
                                              6          6
        R = 6/4 = 1.5 âœ“
        RT = 1.5 + 2.5 = 4 Ω âœ“
      2. V = IR
        I = 2/4 âœ“ = 0.5 A âœ“
      3. V = IR
           = 0.5 x 2.5 âœ“
           = 1.25 v âœ“
  2.  
    1.  
      NM2021 Phys PP2 ET2 ans12
    2. Virtual âœ“/ magnified  âœ“ / same side as object.
    3.  
      1. Reciprocal of forces length âœ“ /power of the lens
      2. Gradient = 1/f  âœ“
        G =   1.0    = 0.1
               20−10
        1/f = 0.1
        f =  = 10 cm  âœ“
            0.1
      3. V = u = 20cm  âœ“ (when m = 0)
      4. 1/f = 1/u1/v
        f = âˆ’ 20 cm
        u = + 10cm
        1/v = âˆ’1/f âˆ’ 1/v 
        1/20 âˆ’ 1/10  âœ“  = âˆ’1−2−3
                                      20       20
        V = 6.67 cm âœ“
  3.  
    1. Refractive index of water nw4/3 
      ​Refractive index of gas ng = 3/2
      ​Refractive index of glass w.r.t. water ngw = ng 
                                                                          nw
      ⟹ ngw = 3/2 Ã· 4/39/8 
    2.  
      1. n = sin i
              sin r
        1.6 = sin 35.6  âœ“
                    1.6
        Sin r = sin 35.6
                       1.6
        r = 21.3° âœ“
      2. Angle of incident = 38.7°✓
      3.  
        NM2021 Phys PP2 ET2 ans14b
      4.  
        • Angle of incidence must be âœ“ greater than critical angle.
        • light must be travelling from dense medium to less dense medium âœ“
  4.  
    1.  
      1.  
        • The time taken for n number of claps.
        • The claps should coincide with the echoes. âœ“
        • The distance between the student and the wall. âœ“
      2. Distance trans = 2d âœ“
        The time taken by the echo = t seconds âœ“
        Speed = 2t/t
      3. 200m âœ“
        • 10cm is short distance and timing is inaccurate.
        • 500m is too long for sound to travel though and be reflected back. Energy lost a long the way. âœ“
    2.  
      1.   
        NM2021 Phys PP2 ET2 ans15b
      2. When the sound goes through the balloon it is focused to one point, hence changing the position the sound become less. âœ“
      3. V = f λ
        λ = v/f =  240 ✓ = 0.333m âœ“
                     1020
  5.  
    1.  
      • When the switch is closed current increases hence there is a change in magnetic flux hence an emf is induced. âœ“
      • When the switch âœ“ is opened current decreases hence there is a change in magnetic flux linkage An emf is induced in the opposite direction âœ“
    2.  
      1. A soft non core reduces losses due to eddy current. ✓It is easily magnetized and demagnetized✓
      2. A laminated core reduces losses due to eddy current âœ“ which can cause overheating. âœ“
    3.  
      1. Vp = Np âˆ’ 400 = 2000
        Vs    Vs       V     200
        P = IsVs 
        Is = 800✓ = 2 A✓
              400
      2. power input = power output
        Pp = IpVp âœ“
        Ip = 800 = 2A
               400

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