## Physics Paper 2 Questions and Answers - Kangundo Subcounty Pre Mock Exams 2021

INSTRUCTIONS TO STUDENTS

1. Write your name and admission number in the spaces provided
2. Answer all questions in this question paper.
3. All your answers and working must be written in the spaces provided in this question paper.
4. This paper consists of 13 printed pages
5. All questions must be answered in English

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

1. State two differences between the images formed by plane mirrors and those formed by pin-hole cameras. (2 marks)
2. The figure below shows a circuit that can be used to magnetize a given bar. Complete the circuit to show the direction of the current around the bar that will result the polarities shown. (1 mark) 3. The figure below shows water waves formed on a ripple tank using two dippers connected to the same vibrator. 1. Show alongside the figure, the resultant of the waves when they merge. (1 mark)
2. Give an explanation for your answer in (i) above. (1 mark)
4.
1. A ray of light moves from an optically denser medium to an optically less dense medium at an angle without being totally internally reflected in the optically denser medium. Give a possible reason for this observation. (1 mk)
2. Give one use of optical fibre in the field of medicine. (1 mk)
5. An electromagnet is used in making an electric bell. State the reason why soft iron is preferred to steel for use as the core. (2 mks)
6. State the main difference between sound waves and water waves. (1 mk)
7. An electric device has a resistance of 40Ω. When connected to a 240V mains supply, it takes a current of 10A. Determine the heat energy dissipated in 1.5 minutes. (3 mks)
8. Four capacitors, A, B, C and D are connected as shown below. State the capacitors that will acquire equal amount of charge. (1 mk)
9. The figure below shows a highly negatively charged rod being brought slowly towards the cap of a positively charged electroscope. It is observed that the leaf initially falls then rises afterwards. Explain the behavior of the leaf. (2 mks)
10. In determining the depth of an ocean, an echo sounder produces ultrasonic sound. Give a reason why ultrasound is preferred to audible sound wave. (1 mk)
11. The figure below shows a stationary wave along a string. 1. Label on the diagram, the nodal points N and the antinodal points, A. (1 mk)
2. If the distance between an antinode and the nearest node is 1.0 x 10-3 m, determine the wavelength of the stationary wave. (2 mks)
12. Eight identical cells can be arranged in series to produce a total e.m.f of 12V just like a car battery.
1. State the e.m.f of one such cell in the arrangement. (1 mk)
2. Why is it possible to start a car engine of a vehicle with a lead acid accumulator, but not with eight such dry cells arranged in series? (1 mk)
3. State one advantage of the lead acid accumulator over an alkaline cell. (1mk)
13. Supermarkets mount large convex mirrors to improve on security monitoring. Give a reason why convex mirrors are preferred over others in this application. (1 mk)
14. Two identical steel pins placed to hang on the south pole of a magnet appear as shown. Explain the appearance of the pins. (1 mk)

SECTION B (55 MARKS)
Answer all the questions in this section in the spaces provided.
15.
1. State Snell’s Law as applied in the study of light. (1 mk)
2. In an experiment to verify Snell’s law, a student obtained different values of angle of incidence and corresponding values of angle of refraction. The results obtained were used to plot the graph shown below. 1. Determine the slope of the graph. (2 mks)
2. State the significance of the slope in the experiment. (1 mk)
3. A ray of light is observed to move from medium A to medium B as shown below. State and explain the change in velocity of the light wave as it moves from medium A to medium B. (2 mks)
4. A lake seems to be 20 m shallower than its actual depth. If the refractive index of water is 1.33, determine the real depth of the lake. (2 mks)
5. Briefly explain the formation of a mirage. (3 mks)
16.
1.
1. A metallic body shaped as shown in the figure below is positively charged and insulated from the ground as shown below. Show the charge distribution on the conductor. (1 mk)
2. A sharp pin connected by a wire to the dome of a van-de-Graaf generator producing positive charges. When the sharp end of the pin is brought near a candle flame, the flame is blown away from the point of the pin. Explain this observation. (2 mks)
2. Two point charges are placed close but not touching each other as shown below. Draw the electronic field around them. (1 mk) 3.
1. Define the term capacitance and state its SI unit. (2 mks)
2. A voltmeter is connected across a charged parallel plate capacitor as shown below. Explain the observation made on its voltmeter when the distance between the plates is reduced. (2 mks)
4. The figure below shows three capacitors connected in series in an electric circuit. Show that the effective capacitanceC_T, is given by the expression. (3 mks)
1  =++
CT   C1  C2  C3
17.
1. Define the term ‘Principal focus’ in reference to a concave lens. (1 mk)
2. You are provided with the following apparatus to determine the focal length of a lens.
• A biconvex lens and a lens holder
• A lit candle
• A white screen
• A metre rule
1. Draw a diagram to show how you would arrange the above apparatus to determine the focal length of the lens. (2 mks)
2. Describe the procedure you would follow in performing the experiment. (2 mks)
3. State the two measurements that you would take. (2 mks)
4. Explain how the measurements in (iii) above would be used to determine the focal length of the lens. (2 mks)
3. An object placed 15 cm from a convex lens is magnified two times. Determine the focal length of the lens. (3 mks)
18.
1. State one advantage of connecting lamps in parallel and not in series in a house wiring. (1 mk)
2. The graph below shows how the terminal voltage of a certain cell varied with the current being drawn from the cell in a laboratory experiment. 1. In the space provided below, draw a circuit diagram that could be used to obtain the results represented by the graph. (1 mk)
2. Write an expression relating the e.m.f, E, terminal voltage, V, current I and the internal resistance, r, for the circuit you have drawn. (1 mk)
3. From the graph, determine the;
1. e.m.f of the cell. (1 mk)
2. Internal resistance of the cell. (3 mks)
3. In the figure below, A reads 0.6 A. Determine the:
1. effective resistance in the circuit. (2 mks)
2. total voltage in the circuit. (1 mk)
3. current in the 4Ω resistor. (1 mk)
4. voltmeter reading. (2 mks)
19.
1. State two factors that determine the amount of heat produced by an electric current. (1mk)
2. The figure below shows a circuit with a coil used to warm oil in a beaker. 1. Explain how heat is produced in the coil (2mks)
2. Given that the reading of the ammeter is 2.4A determine the resistance of the coil. (2 mks)
3. How much heat is produced in the coil in a minute? (3mks)

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