# Physics Paper 2 Questions and Answers - Eagle II Joint 2021 Mock Exams

INSTRUCTIONS TO THE CANDIDATES

• Mathematical tables and silent non-programmable calculators may be used.
• This paper consists of section A and section B.
• Answer all the questions in section A and section B in the spaces provided.
• All working must be clearly shown.

For Examiners Use Only: -

 SECTION QUESTION MAXIMUM SCORE CANDIDATE’S SCORE A 1-10 25 B 11 13 12 10 13 12 14 12 15 8 TOTAL SCORE 80

## QUESTIONS

SECTION A (25 MARKS)

1. State and explain the effect of polarization in the performance of a simple cell. (2 marks).
2. Explain why eight dry cells in series cannot be used to start a car engine even though they have the same e.m.f. as the lead acid accumulator (1 mark)
3. Figure 1.0 below shows a ray of light incident along the normal. The mirror is rotated at an angle of 15º in a clockwise direction without changing the position of the incident ray.

Fig. 1.0
Determine the angle between the reflected ray and the incident ray. (2 marks)
4. A battery of e.m.f E drives a current of 0.25A when connected to a 5.5 W resistor. When the 5.5 W resistor is replaced with 2.5 W resistor the current flowing becomes 0.5 A. Find the emf, E and the internal resistance, r, of the battery. (4 marks)
5.
1. Figure 2.0 shows a motor connected to a magnetic switch called a relay operated by an ordinary switch S1. Use the information in the figure to answer questions that follow.

Fig. 2.0
1. Explain how the relay switches on the motor when S1 is closed. (3 marks)
2. State with a reason the effect on the motor if the iron core is replaced with a steel core and switch S1 is put on and then off. (2 marks)
6. A negatively charged rod is brought near the cap of a leaf electroscope. The electroscope is then earthed momentarily by touching with the finger. Finally, the rod is withdrawn. State and explain the observation made. (2 marks)
7. State any two ways of in increasing the size of an image formed by a fixed pinhole camera. (2 marks)
8. The figure 3.0 below shows a circuit that can be used to verify Ohm’s law

Fig. 3.0
Explain briefly how the setup can be used to verify ohm’s law (3 marks)
9. Other than progressive waves travelling in opposite direction at the same speed, state any other two conditions necessary for the formation of stationary wave (2 marks)
10. Arrange the following radiations in order of their wavelengths: infrared, blue light, ultraviolet, radio waves, X-rays. (2 marks)
SECTION B (55 MARKS)
11.
1. Distinguish between transverse waves and longitudinal waves. (2 marks)
2. Plane water waves travels from a deep end into a shallow end in a swimming pool at a velocity of 4m/s. if the wavelength of these waves in deep end is 6cm and in the shallow end is 1.5cm, determine the velocity of these waves in the shallow end. (3 marks)
3. State one factor that affects the velocity of sound in a solid. (1mark)
4. A disc siren with 200 holes is rotated at constant speed making 0.5 revolutions per second. If air is blown towards the holes, calculate:
1. The frequency of sound produced. (3marks)
2. The wavelength of the sound produced if velocity of sound in air is 340ms-1 (2 marks)
5. State one way of reducing echoes in a room? (1 mark)
12.
1. State one major reason why prisms are preferred over mirrors in periscopes. (1 mark)
2. Figure 4.0 below shows a ray of light incident on one side of a glass prism. Complete the ray diagram to show how the ray is dispersed. (3 marks)

Fig.4.0
3. Light travels from water at a velocity of 2.26x108 ms-1 and enter glass travelling at a velocity of 2.0x108ms-1 Calculate the refractive index of glass with respect to water. (3 marks)
4. In a transparent liquid container, an air bubble appears to be 18cm when viewed from end A and 12cm when viewed from end B as shown in figure 5.0 below. Where exactly is the air bubble. If the length of the tank is 40cm? (3 marks)

Fig. 5.0
13.
1. State two factors that determine the capacitance of a parallel plate capacitor (2 marks)
2. Figure 6.0 below shows four capacitors connected to a battery of 12 volts.

Fig. 6.0
Calculate:
1. effective capacitance. (3 marks)
2. charge on 3.2μF (2 marks)
3. p.d across 5μF (2 marks)
4. the energy stored by 2μF (2 marks)
3. Give one application of capacitors (1 mark)
14.
1. An object O stands on the principal axis of a concave mirror as shown in figure 7.0 below.

Fig 7.0
2. By drawing suitable rays, show the position of the image (3 marks)
3. Determine the magnification of the image formed (2 marks)
4. In an experiment to determine the focal length of a converging lens, a group of form four students collected some data and used the results to plot the graph shown in figure 8.0 below.

Fig 8.0
Using the graph above, determine:
1. The object position when the image position is 45 cm (3 marks)
2. Slope of the graph. (2 marks)
3. The focal length of the lens given m = v/f - 1 (2 marks)
15.
1. The figure 9.0 below shows a circuit with a coil used to warm oil in a beaker.
Fig 9.0
1. Explain how heat is produced in the coil (2 marks)
2. Given that the reading of the ammeter is 2.4A determine the resistance of the coil. (3 marks)
3. How much heat is produced in the coil in a minute? (3 marks)

## MARKING SCHEME

SECTION A (25 MARKS)

1. State and explain the effect of polarization in the performance of a simple cell. (2 marks).
It insulates the positive electrode with hydrogen bubbles. This minimizes the flow of charges through the electrode, reducing the efficiency of the cell.
2. Explain why eight dry cells in series cannot be used to start a car engine even though they have the same e.m.f. as the lead acid accumulator (1 mark)
Dry cells have high internal resistance which reduces the amount of current being produced by the cells series
3. Figure 1.0 below shows a ray of light incident along the normal. The mirror is rotated at an angle of 15º in a clockwise direction without changing the position of the incident ray.

Fig. 1.0
Determine the angle between the reflected ray and the incident ray. (2 marks)
x = 2θ
= 2 x 15º
= 30º
4. A battery of e.m.f E drives a current of 0.25A when connected to a 5.5 W resistor. When the 5.5 W resistor is replaced with 2.5 W resistor the current flowing becomes 0.5 A. Find the emf, E and the internal resistance, r, of the battery. (4 marks)
E= IR + Ir                            E=1.25 +0.5r……(ii)
E= (0.25x 5.5) + 0.25r        solving (i) and (ii)                              r= 0.5Ω
E= 1.375 + 0.25r…(i)         1.25 +0.5r = 1.375 + 0.25r                 E= 1.25 + (0.5 x 0.5)
E= (2.5 x 0.5) + 0.5r           0.25r =0.125                                      E=1.5 Volts
5.
1. Figure 2.0 shows a motor connected to a magnetic switch called a relay operated by an ordinary switch S1. Use the information in the figure to answer questions that follow.

Fig. 2.0
1. Explain how the relay switches on the motor when S1 is closed. (3 marks)
On closing the switch, current flows and the core is magnetized. It attracts the soft iron armature which turns at the pivot and joins the contacts. Current flows switching on the motor
2. State with a reason the effect on the motor if the iron core is replaced with a steel core and switch S1 is put on and then off. (2 marks)
Motor would rotate continuously. Steel would be magnetized permanently hence contact is not broken after opening the switch.
6. A negatively charged rod is brought near the cap of a leaf electroscope. The electroscope is then earthed momentarily by touching with the finger. Finally, the rod is withdrawn. State and explain the observation made. (2 marks)
The leaf divergence decreases first. On earthing negative charges are repelled to the ground. When the rod is withdrawn, the electroscope is left with a net positive charge, hence the leaf divergence increase
7. State any two ways of in increasing the size of an image formed by a fixed pinhole camera. (2 marks)

- Increasing the size of the object
-Reducing the distance of the object from the pin-hole.

8. The figure 3.0 below shows a circuit that can be used to verify Ohm’s law

Fig. 3.0
Explain briefly how the setup can be used to verify ohm’s law (3 marks)
- Close the switch and read the corresponding values of I and V
- Adjust the Rheostat and record the other corresponding values of I and v in a table.
- Plot a graph of V against I which gives straight line through the origin and hence V is directly proportional to I.
9. Other than progressive waves travelling in opposite direction at the same speed, state any other two conditions necessary for the formation of stationary wave (2 marks)
- Must have the same amplitude
-Must have the same frequency
10. Arrange the following radiations in order of their wavelengths: infrared, blue light, ultraviolet, radio waves, X-rays. (2 marks)
2 marks for correct order
X-rays, Ultraviolet, Blue light, Infrared, Radio waves,

SECTION B (55 MARKS)
11.
1. Distinguish between transverse waves and longitudinal waves. (2 marks)
Transverse waves are waves in which the vibration of particles is perpendicular to the direction in which the wave travel. While longitudinal waves are waves in which the vibration of particles is parallel to the direction in which the wave travel.
2. Plane water waves travels from a deep end into a shallow end in a swimming pool at a velocity of 4m/s. if the wavelength of these waves in deep end is 6cm and in the shallow end is 1.5cm, determine the velocity of these waves in the shallow end. (3 marks)
V1λ1
V2   λ2
V2 = 4m/s x 0.015m
0.06m
= 1 m/s
3. State one factor that affects the velocity of sound in a solid. (1mark)
-the temperature             one mark for any correct answer
- the density of the solid.
4. A disc siren with 200 holes is rotated at constant speed making 0.5 revolutions per second. If air is blown towards the holes, calculate:
1. The frequency of sound produced. (3marks)
Frequency = no. of revolutions x no. of holes
=0.5 x 200
= 100Hz
2. The wavelength of the sound produced if velocity of sound in air is 340ms-1 (2 marks)
V=fλ
λ = 340/100
= 3.4m
5. State one way of reducing echoes in a room? (1 mark)
-by covering seats, walls, the floor and the ceiling with soft sound absorbing materials.
12.
1. State one major reason why prisms are preferred over mirrors in periscopes. (1 mark)
-Mirrors form blurred images due to multiple reflections at their surfaces
2. Figure 4.0 below shows a ray of light incident on one side of a glass prism. Complete the ray diagram to show how the ray is dispersed. (3 marks)

Fig.4.0
Splitting of rays inside the prism
Correct colours i.e. dispersion red and violet
3. Light travels from water at a velocity of 2.26x108 ms-1 and enter glass travelling at a velocity of 2.0x108ms-1 Calculate the refractive index of glass with respect to water. (3 marks)
n= velocity of light in water /velocity of light in glass
= 2.26 x 108
2.0 x 108
n =1.13
4. In a transparent liquid container, an air bubble appears to be 18cm when viewed from end A and 12cm when viewed from end B as shown in figure 5.0 below. Where exactly is the air bubble. If the length of the tank is 40cm? (3 marks)

Fig. 5.0
Let the bubble be Xcm from point  A
= real depth
apparent depth
= x  cm = (40 - x) cm
18 cm     12 cm
12x = 18(40 - x)        = 30x = 720
30      30
x = 24 cm

Therefore, the bubble is 24cm from A and 16cm from B
(Note a student may use Xcm to be the distance of the bubble from B)

13.
1. State two factors that determine the capacitance of a parallel plate capacitor (2 marks)

-area of plates     ( two marks for any two correct)
-nature of dielectric material.
-distance between the plates

2. Figure 6.0 below shows four capacitors connected to a battery of 12 volts.

Fig. 6.0
Calculate:
1. effective capacitance. (3 marks)
= 2 x 8 = 1.6
2 + 8
1.6 + 3.2 = 4.8
CT = 5 x 4.8       24 = 2.45  = 2.45 x 10-6F
5 + 4.8      9.8
2. charge on 3.2μF (2 marks)

Q = CV
= 2.45 x 10-6 x 12 = 2.94 x 10-5C
charge on 3.2μF = 3.2/4.8 x 2.94 x 10-5
= 1.96 x 10-5C

3. p.d across 5μF (2 marks)
p.d on 5uf = σ/c
= 2.94 x 10-5 = 5.88 volts
5 x 10-6
4. the energy stored by 2μF (2 marks)
energy=1/2 CV^2
= ½ x 2 x 10-6 x 6.122
= 3.75 x 10-5J
3. Give one application of capacitors (1 mark)

(two marks for any two correct)

- smoothening rectified circuits
- Reduction of sparking in induction coils in tuning
-Circuits /delay /camera flash

14.
1. An object O stands on the principal axis of a concave mirror as shown in figure 7.0 below.

- Correct rays (real and virtual rays with arrows shown by complete and broken lines) 
- Image shown by broken lines

Fig 7.0
2. By drawing suitable rays, show the position of the image (3 marks)
3. Determine the magnification of the image formed (2 marks)
magnification = image height = 2.8 = 2.54
object height    1.1
= 2.545
4. In an experiment to determine the focal length of a converging lens, a group of form four students collected some data and used the results to plot the graph shown in figure 8.0 below.

Fig 8.0
Using the graph above, determine:
1. The object position when the image position is 45 cm (3 marks)

V = 45cm m = 3.5
M = v/u
3.5 = 45/u
U = 45/(3.5)
= 12.85cm

2. Slope of the graph. (2 marks)

Slope = (3.5-0)/(45-10)
=  (3.5)/35
= 0.1 cm

3. The focal length of the lens given m = v/f - 1 (2 marks)
f = 1/slope
= 1/(0.1)
= 10cm
15.
1. The figure 9.0 below shows a circuit with a coil used to warm oil in a beaker.
Fig 9.0
1. Explain how heat is produced in the coil (2 marks)
when the switch is switched on the current flowing through the conductor encounters a lot of resistance in the heating coil. As a result, some of the electrical energy is converted into heat energy (as the electrons collide with the atoms)
2. Given that the reading of the ammeter is 2.4A determine the resistance of the coil. (3 marks)
V = IR
12 = 2.4 x R
R = 12
2.4
R = 5Ω
3. How much heat is produced in the coil in a minute? (3 marks)
Alternatively
H=(V2t)/R                       H=I2Rt
=(122 x 60)/5                 H=(2.4)2 x 5x 60
=1728 joules                 H=1728 joules

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