NAME____________________________________CLASS_______INDEX. NO.________

DATE___________________________CANDIDATE’S SIGNATURE________________

232/2PHYSICSPaper 2August Holiday Assignments Form 4 20172 Hours

Kenya Certificate of Secondary EducationPHYSICSPaper 22 Hours

Write your name, class and index number in the spaces provided above.This paper consists of TWO sections: Sections A and B.Answer ALL the questions in sections A and B in the spaces provided.ALL working MUST be clearly shown.Mathematical tables and electronic calculators may be used.

Take: Velocity of sound in air = 340 m/s Velocity of light in vacuum = 3.0 ×108 m/s

For Examiner’s Use Only

SECTION QUESTION MAXIMUM SCORE

CANDIDATE’S SCORE

A 1-13 25

B

14 1215 1016 1217 0718 14

TOTAL SCORE 80

This paper consists of 10 printed pages.Students should check the question paper to ensure that all the pages are printed as indicated and no

questions are missing.

SECTION A (25Marks)

Answer ALL questions in this section in the spaces provided.

1. State two advantages of an alkaline battery over lead acid battery. [2Marks]

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2. A 240V mains supply is fitted with a 13A fuse. Determine the number of 800W electric fires that could safely be connected to the supply. [3Marks]

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3. The figure below shows a positive charge near a plate carrying a negative charge.

On the diagram, draw the electric field lines between them. [2Marks]

4. If the shortest length of the closed tube for resonance is 0.12m and the next resonant length is 0.37m, calculate the frequency of vibration. [3Marks]

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5. Two plane mirrors are placed at an angle of 00 facing each other. Calculate the number of images formed. [2Marks]

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6. The circuit below consists of ideal diodes D1 and D2.

8 Ω 6 Ω

20 V

D1 D2

4 Ω

Determine the current flowing through the resistors. [2Marks]

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7. The focal length of a concave lens is 25 cm. Calculate the power of the lens. [2Marks]

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8. A convex mirror of focal length 18cm produces an image on its axis, 6cm away from the mirror. Calculate the position of the object. [3Marks]

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9. How is the intensity of x-rays increased in the x-ray tube? [1Mark

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10. Arrange the following electromagnetic waves in ascending energy which they posses. [2Marks]

Radio waves, Gamma rays, Blue light, Infra-red radiation, Microwaves and Green light.

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11. Give one use of radioactivity in agriculture. [1Mark]

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12. As the steel nail is electrically magnetized, the number of iron nails attracted increases as the magnetizing current is increased. However, after sometime, the steel nail can no longer attract more pins. Explain this observation using the domain theory. [1Mark]

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13. Explain how the velocity of sound in air is affected by the density of air. [1Mark]

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SECTION B (55Marks)

Answer ALL questions in this section in the spaces provided.

14. a] State Ohm’s law and give an example of a non-ohmic conductor. [2Marks]

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b] Study the circuit diagram below and answer the following questions.

2 V

6 Ω

2.5 Ω Y 3Ω Z X

6Ω

i] Calculate the effective resistance between Y and Z. [3Marks]

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ii] Determine the current through the 3 resistors. [5Marks]

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iii] One of the 6 resistors has a length of 1.0m and cross-section area of 5.0 x 10-6 m2. Calculate the resistivity of the material. [2Marks]

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15. a] State Snell’s law for refraction of light. [1Mark]

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b] The figure below shows the path of a ray of yellow light through a glass prism. The speed of yellow light in the prisms is 1.88 x 108 m/s.

600 Ɵ r

i] Determine the refractive index of the prism material for the light. [3Marks]

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ii] Show on the figure the critical angle, c, and determine its value. [3Marks]

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iii] Given that r = 21.2o, determine the angle . [2Marks]

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iv] On the same figure, sketch the path of the light after striking the prism if the prism was replaced by another of similar shape but lower refractive index. [Use dotted line for your answer] [1Mark]

16. a] Figure below shows the features of a cathode ray tube.

B Cathode A Anodes X-plates

(-) (-) (+) (+) Y-plates Beam Fluorescent screen

i] Name the parts labeled A and B. [2Marks]

A …………………….........……....………. B…......................………………………….

ii] Explain how the electrons are produced in the tube. [2Marks]

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iii] State two functions of the anodes. [2Marks]

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iv] At what part of the cathode ray tube would the time-base be connected? [1Mark]

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b] The graph below was obtained on a cathode ray oscilloscope (CRO) screen when the output of an a.c. generator was connected to the input of the CRO. The time- base calibration of the CRO was set at 20 milliseconds per centimeter and the y- gain at 5 volts per centimeter.

i] Determine the peak-voltage of the generator [1Mark]

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ii] Determine the frequency of the voltage [2Marks]

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iii] On the same grid, redraw the graph for the same voltage when the time base calibration is set at 40 milliseconds per centimeter and y- gain at 10 volts per centimeter. [Show at least one cycle] [2Marks]

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17. a] The figure shows two circuits close to each other.

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. [3Marks]

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b] An ideal transformer has 2000 turns in the primary circuit and 200 turns in the secondary circuit. When the 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:i] The secondary circuit. [2Marks]

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ii] The primary circuit. [2Marks]

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18. a] Explain how photoelectric effect can be demonstrated with the help of a charged gold leaf electroscope, photocell and milliammeter. [3Marks]

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Coils

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b] What is meant by the term work-function? [1Mark]

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c] In an experiment to determine the Kinetic energy of the emitted electrons from a metal surface by photoelectric effect, the following results were obtained.

Frequency , f (×1014 Hz) 7.0 6.5 6.3 6.0 5.5 5.0

Kinetic Energy , K.E. ¿J¿ 1.65 1.34 1.17 1.00 0.65 0.36

i] Plot a graph of Kinetic Energy , K .E . against frequency , f . [5Marks]

ii] From the graph, determine:

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I] The Planck’s constant,h . [3Marks]

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II] The threshold frequency, f O of the radiation. [1Mark]

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III] The work-function, W O of the metal. [1Mark]

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