Physics Paper 2 Questions and Answers - Chogoria Murugi Zone Pre Mock Exams 2023

Instructions to Candidates

This paper consists of two sections A and B.
Answer all the questions in section A and B in the spaces provided
All working MUST be clearly shown in the spaces provided in this booklet.
Non programmable silent electronic calculators and KNEC mathematical tables may be used except where stated otherwise.
Take: Speed of light in vacuum C = 3.0 x 10⁸m/s
Acceleration due to gravity g = 10N/S²

SECTION A (25 MARKS)
Answer all the questions in the spaces provided.

Figure 1 below shows a ray of light incident to the first of the two mirrors placed at an angle of 60°C

Complete the path of the ray after reflection from the mirrors. (1 mk)
Figure 2 below shows a positive charge near a plate carrying negative charge.

Draw the electric field between them. (2mks)
Two pins are hanging from a magnet as shown in the diagram below (figure 3)

Explain why they do not hang vertically downwards. (2mks)
Draw the diagrams to illustrate what happens when plane waves are incident on a slit.
1. When the width of the slit is large compared with the wavelengths of the waves. (2mks)
2. When the width of the slit is small compared with wavelength of the waves. (2mks)
What energy conversion occurs in a photocell? (1mk)
1. Arrange the following waves in order of decreasing wavelength; infrared, X-rays, micro-waves and visible light. (1mk)
2. State one application of visible light. (1mk)
State two advantages of an alkaline battery over lead acid battery. (2mks)
A girl shouts and ears an echo after 0.6 seconds later from a cliff. If velocity of sound is 330m/s, calculate the distance between her and the cliff. (3mks)
What is dispersion of light? (1mk)
Determine the reading of an ammeter in figure 4 below(2mks)
A ray of light is incident on a glass oil interface as shown in figure 5 below. Determine the value of r (Take refractive index of glass and oil as 3/2 and 6/3 respectively) (3mks)
State two factors that affect the capacitance of a parallel plate capacitors(2mks)

SECTION B (55 MARKS)

1. State Ohm’s law. (1 mark)
2. You are provided with the following apparatus:
  - Connecting wires
  - An ammeter
  - Fixed resistor
  - A voltmeter
  - A variable resistor
  - Switch
  - 2 dry cells in a cell holder
    1. In the spaces below, draw the circuit that can be used using the apparatus above to verify Ohm’s Law. (3 marks)
    2. Briefly explain how you can obtain the results to verify Ohm’s law. (4 marks)
3. Study the circuit diagram below and answer the questions that follow.
  1. Calculate the effective resistance of the circuit. (3 marks)
  2. Find the voltmeter reading. (2marks)
1. A Girl stands some distance from a high wall and claps her 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 (3mks)
  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 distances (2mks)
  4. 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)
2. Figure 15 shows the set up used to demonstrate interference of sound
  1. An observer O, moves along XY.
    State the observation(s) made. (1 mark)
  2. State what would be observed if a cathode ray oscilloscope is moved along line XY. (1 mark)
  3. What will a student hear if he moves along the line OC? (1 mark)
1. State the conditions to be satisfied for total internal reflection to occur.
2. A ray of light traveling in the direction EO in air enters a rectangular block as shown in the diagram. The resulting angle of refraction is 18°.
  
  Find:
  1. The refractive index of the block. (2marks)
  2. The critical angle C of the block. (3marks)
1. The figure below shows an object in front of lens.
  1. Using rays locate the image as seen by observer, E. (2marks)
  2. Give one application of such a lens as used above. (1 mark)
2. Figure below shows a diagram of the human eye. Sketch a ray diagram showing how lens is used to correct long sightedness(2 marks)
3. An object of height 10.5cm stands before a diverging lens of focal length 20cm and a distance of 10cm from the lens. Determine;
  1. image distance. (3 marks)
  2. height of the image. (3 marks)
  3. magnification. (2 marks)
1. State the Lenz’s law of electromagnetic induction. (1 mark)
2. A bar magnet is moved into a coil of an insulated copper wire connected to a zero centre galvanometer as shown below
  1. Show on the figure above the direction of the induced current in the coil. (1 mark)
  2. State and explain what is observed on the galvanometer when the south pole of the magnet is moved into and then withdrawn from the coil. (2 marks)
3. A transformer has 800 turns in the primary and 40 turns in the secondary winding. The alternating voltage connected to the primary is 240V and current of 0.5.A. If 10% of the power is dissipated as heat within the transformer, determine the current in the secondary coil.
  (3 marks)

MARKING SCHEME

They acquire North poles at the ends thus they repel.
Light energy to electrical energy
1. Microwaves, infrared, visible light, x – rays
2. - Observing objects
  - Taking pictures
Alkaline
- Produces higher current
- Lasts longer
- It is portable
- Less maintenance & care
V = ²⁵/_t, ⇒ S = ^Vt/₂
S = 330 × 0.6 = 99m
2
Separation of colours of light from white light.
I = ^V/_R= ²/₆ = ¹/₃= 0.33A
_an_g = ³/₂, _an_o = ⁶/₃
∴ _on_g = _on_a an_g
= ³/₆ × ³/₂
= ⁹/₁₂ = ³/₄
= ³/₄ or 0.75
- Distance between the plates
- Area of plates
- Dielectric material used

SECTION B

1. For an atomic conductor p.d across the ends is directly proportional to current if temperature and other constants kept constant ;
2. 1. Ammeter in series ;
    Voltmeter in parallel
    Variable resistor in series
    (apparatus must be workable)
  2. - Connect the apparatus as shown
    - Vary variable resistor such that I is certain value ;
    - Record I in ammeter and V in Voltmeter ;
    - Draw graph of V against I ;
3. 1. Parallel ^I/_R = ¹/₆ + ¹/₄ + ¹/₈
    ^I/_R = 2+3+4
    12
    ^I/_R = ⁹/₁₂
    R = 4 = l ¹/₃Ω
    R₁= 4+1¹/₃= 5¹/₃Ω
  2. V = IR
    I =^V/_R= ^4.5/_5.33
    = 0.844A
    =3.377V
1. 1. Time taken for n number of claps. The claps should concide with the echos; The distance between the civil and walls;
  2. Sound has to travel to the walls and reflected back to the coil
    Distance travelled is 2d;
    For n claps there will be n echo’s;
    Total distance travelled = n x 2d = 2nd;
    Speed of sound = 2nd ;
    t
  3. 200m;
    10m is short distance and timing will be inaccurate;
    500m is too long for sound to travel through and be reflected back. Energy will have been lost along the way;
  4. V = fλ
    340 = 10.20 × λ;
    λ = 340
    1020
    = 0.3333m
2. 1. Destructive and constructive interference
  2. Maximum amplitude or horizontal line
  3. Loud sound all through
1. 1. Light must travel from denser medium to less dense medium.
  2. Angle of incidence in the denser medium must be greater than critical angle in the less dense medium.
2. 1. sin i = n
    sin r
    sin30° = 1.618
    sin 18°
    n = 1.618
  2. sin C = ¹/_n
    sin C = 1
    1.618
    C=sin^-1 0.61804
    C = 38.17°
1. 2. As a magnifying glass.
3. 1. ¹/_V + ¹/_U = ¹/_f f = −20 U= +10
    ¹/_V = ⁻¹/_f − ¹/_U ✓1
    = ⁻¹/₂₀ − ¹/₁₀ = (−1−2)
    20
    =⁻³/₂₀V = 6.67cm ✓1
  2. Image height = Image distance × Object height
    Object distance
    HI = V × H₀ ✓1
    U
    = 6.67 × 10.5
    10
    = 7.00cm ✓1
  3. M = ^V/_U = ^6.67/₁₀ = 0.667cm ✓1
1. State the Lenz’s law of electromagnetic induction. (1 mark)
  - The direction of induced e.m.f is such that the induced current that it causes to flow produces a magnetic effect which opposes the charge producing it✓
2. A bar magnet is moved into a coil of an insulated copper wire connected to a zero centre galvanometer as shown below
  1. Show on the figure above the direction of the induced current in the coil (1mark)
  2. State and explain what is observed on the galvanometer when the south pole of the magnet is moved into and then withdrawn from the coil. (2 marks)
    - The pointer deflects in one direction and comes back to zero. ✓When magnetic fields cut through the conductor, emf is induced which makes the current to flow and the pointer deflect but comes back to zero when there is no relative motion between the coil and the magnet✓
3. A transformer has 800 turns in the primary and 40 turns in the secondary winding.
  The alternating voltage connected to the primary is 240V and current of 0.5.A. If 10% of the power is dissipated as heat within the transformer, determine the current in the secondary coil. (3 marks)
  N_G = Vₛ
  N_P N_P
  40 = Vₛ . ✓
  800 240
  Vₛ = 40 + 240 = 12V
  800
  VₛIₛ × 100 = 90✓
  V_pI_p
  Iₛ = 0.9 × 240 × 0.5 = 9A✓