Physics Paper 2 Questions and Answers - Form 3 End Term 2 Exams 2022

QUESTIONS

SECTION A: (25 MARKS)

1. Under which condition is the potential difference across the terminal of a cell equal to its e.m.f? (1mk)
2. The figure below shows a ray of light incident on a plane mirror
   
   Determine the angle of reflection when the mirror is rotated 10º anticlockwise (2mks)
3. A soldier standing some distance from a wall blows a whistle and hears its echo 1.8 seconds later. How far is the wall from the soldier? (Speed of sound in air = 330ms^-1) (3mks)
4. Other than temperature, state any other factor that affects the resistance of an ohmic conductor (1mk)
5. Using the domain theory, differentiate between magnetic and non-magnetic materials (1mk)
6. The figure below shows circular waves approaching a plane barrier.
   
   On the same diagram, sketch the reflected rays (1mk)
7. State one application of the following: (2mks)
   1. Convex mirrors
   2. Parabolic mirrors
8. A pin is placed below the surface of transparent water of depth 10cm and refractive index 1.33. Calculate the vertical displacement of the pin (3mks)
9. The figure below shows an arrangement of resistors in a circuit.
   
   Determine:
   1. The effective resistance (2mks)
   2. The voltage drop across the 1Ω resistor (3mks)
10. The figure below shows the image I formed by a concave mirror. Using ray diagrams, locate the position of the object (3mks)
    
11. The figure below shows a displacement-distance graph of a wave travelling at 2ms^-1
    Determine:
    1. The amplitude (1mk)
    2. The wavelength (1mk)
    3. The frequency of the waves (2mks)

SECTION B (55MARKS)

12.      
    1. Draw the electric field pattern between the charges shown below (2mks)
       
    2. State two factors that affect the capacitance of a parallel plate capacitor (2mks)
    3. The figure below shows a network of resistor connected to a 100V power source.
       
       Determine:
       1. The effective capacitance of the circuit (3mks)
       2. The charge on the 16uF capacitor (3mks)
       3. The p.d. across the 12uF capacitor (3mks)
13.      
    1. State the Snell’s law of refraction of light (1mk)
    2. The figure below shows a ray of light travelling from crown glass to air.
       
       Determine:
       1. The refractive index of crown glass (3mks)
       2. The speed of light in crown glass. (3mks)
          (Speed of light in air = 3.0 x 10⁸ms^-1)
    3.      
       1. What would be the effect on the image of increasing the length of a pinhole camera? (1mk)
       2. A girl stands 5m in front of a pinhole camera of length 50cm. If the girl is 1.2m tall, determine the size of her image as formed by the pinhole camera (3mks)
    4. The figure below shows an object in front of a plane mirror. Using rays, locate the image as seen by the eye shown (3mks)
       
14.      
    1. State the Ohms law (1mk)
    2. State the effect on the resistance of a conductor when the conductor is heated (1mk)
    3. Three identical dry cells each of e.m.f 1.6V are connected in series to a resistor of resistance 11.4Ω. If a current of 0.32A is flowing through the circuit, determine:
       1. the total e.m.f of the cells (1mk)
       2. the internal resistance of each cell (3mks)
    4. The figure below shows resistors R1 and R2 connected in parallel. Their ends are connected to a battery of potential difference V volts.
       
       1. In terms of V1, R1 and R2, write an expression for:
          1. Current I1 through R1 (1mk)
          2. Current I2 through R2 (1mk)
          3. Total current in the circuit (1mk)
       2. Show that the total resistance RT is given by (3mks)
          RT = R1R2
                  R1+R2
15.      
    1. State two factors that affect the strength of an electromagnet (2mks)
    2. In the set up shown below, the suspended metre rule is 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 is closed (3mks)
       2. What is the effect of reversing the battery terminals? (1mk)
    3. State one defect of a simple cell and how it is corrected (2mks)
       
16.      
    1. Differentiate between transverse and longitudinal waves (2mks)
    2. State two conditions necessary for two progressive waves travelling in the opposite direction to form stationary waves (2mks)
    3. A wave has a periodic time of 0.2 seconds and a distance of 30cm between successive troughs. Determine the speed of the wave (3mks)

MARKING SCHEME

1.  When the cell is an open circuit
2. r = 30 + (2 x 10)
   = 50º
3. V = ^2d/_t
   d = ^Vt/₂
   =330 x 1.8
   2
   = 297
4. Temperature
   length of conductor
   cross-sectional area of consuctor
5. In magnetic materials, the magnetic domains are aligned
   In non magnetic materials the magnetic domains face in all directions
6.    
   
7.        
   1. As a driving mirror or in supermarts
   2. reflectors
      solar concatrators
8. n = real depths
   apparent depth
   apparent depth = 10/1.33 = 7.52cm
   displacement = 10 - 7.52 = 2.48cm
9.      
   1. 6 + 6
   2. I = V/R
      = 2/4
      = 0.5A
      V = IR
      = 0.5 x 1
      =0.5
10.     
    
11.    
    1. 2cm
    2. 0.5 - 0 = 0.5m
    3. c = fλ
       f = ^c/_λ = ²/_0.5 = 4HZ
12.     
    1.     
       
    2. area of plates
       distance apart of the plates
       dielectric between the plates
    3.    
       1. Parallel C = 16 + 12 = 18μF
          ct = 18 x 6 = 288 = 8.47μF
                 18 + 6    34
       2. Q = CV
          = 8.47 x 10^-6 x 100
          = 8.47 x 10^-4C
13.     
    1. The ratio of sine of the angle of incidence to the sine of the angle of refraction is a constant for a given pair of media
    2.     
       1. C = 90 - 38 = 52º
          n = ¹/_sinC
          = ¹/_sin52º
          = 1.27
       2. n = ^c/_c'
          c' = 3.0 x 10⁸
                    1.27
          =2.36 x 10⁸ms^-1 
    3.     
       1. It would be enlarged but less bright
       2. ^H1/_H0 = ^V/_u 
          ^H1/₁₂₀ = ⁵⁰/₅₀₀
          H1 = 50 x 120
                     500
          =12cm
          or
          H1 = VH₀
                     u
          =0.5 x 1.2
                 5
          =0.12m
    4.     
       
14.     
    1. The current flowing through a metallic conductor is directly proportional to the P.D across its ends provided the temperature and other physical conditions remain constant
    2. It increases
    3.    
       1. 1.6 x 3 = 4.8V
       2. E = I(r + R)
          4.8 = 0.32(r + 11.4)
          4.8 = 0.32r + 3.648
          r = 4.8 - 3.648 = 3.6Ω
                     0.32
          For each cell, r = ^3.6/₃ = 1.2Ω
    4.      
       1.     
          1. I₁ = ^V/_R1
          2. 1₂ = ^V/_R2
          3. IT = I₁ + I₂
       2. I/RT = I/R1 + I/R2 
           1  = R1 + R2
          RT    R1 x R2
          RT = R1 x R2 = R1R2
                  R1 + R2  R1 + R2
15.     
    1. amount of current
       number of turns of the coil
       soft ferromagnetic core
    2.      
       1. when the switch is closed the iron core become magnetised. The upper part of the iron core attains a south pole and attracts the metre rule which turns anticlockwise
       2. The polarity of the iron core is reversed and hence metre rule is repelled turning clockwise
    3. Local action - coat zinc with mercury 
       or
       Polarization - add potassium dichromate solution
16.     
    1. In transverse waves, the vibrations are perpendicular to the direction of travel of the wave whereas in a longitudinal wave, the direction of vibration of the weave is the same direction of travel of the wave
    2. same speed
       same frequency
       same or nearly equal amplitude
    3. V =fλ
       = 5 x 0.3
       1.5ms^-1
       f = ¹/_0.2
       = 5HZ
       λ = 30cm = 0.3M