Name: . ………………………………………..…………….. Index No.:………………………

School:……..………………………………………………… Adm. No ……………………….

232/2

PHYSICS

Paper 2

2017

Time: 2 hours

PHYSICS PAPER 2 PREDICTION 2017 Kenya Certificate of Secondary Education (K.C.S.E)

INSTRUCTIONS TO CANDIDATES

Write your name and index number in the spaces provided above. 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. Mathematical tables and electronic calculators may be used.

FOR EXAMINER’S USE ONLY

Section Question Maximum score Candidates score

A 1 – 13 25

B 14

15

16

17

18

11

10

15

12

7

80

This paper consists of 12 printed pages

Candidates should check the question paper to ensure that all the printed pages are printed as

indicated and no questions are missing.

SECTION A (25 Marks)

Answer all the questions in the spaces provided.

1. State ONE similarity and ONE difference between a camera and a human eye.

.........................................................................................................................................................................................

.........................................................................................................................................................................................

(2 marks)

2. A convex lens forms an image five times the size of the object on a screen. If the distance between the object and the screen is 120cm, determine the focal length of the lens. (2mks)

3. The figure shows three capacitors connected between points A and B

Determine the capacitance between A and B.

[2m] [Total 2m]

4. Figure 1 below shows a soft iron rod placed between two poles of a magnet

On the same figure sketch the magnetic field lines between the poles. (2mks)

5. A long flexible wire is wrapped round two wooden pegs. A large current is passed in the direction shown.

Which two pairs of lengths of wire attract each other? First pair

.........................................................................................................................................................................................

Second pair

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[2m]

6. A stationary wave of frequency 80.0 Hz is set up on a stretched string of length 210 cm.

What is the speed of the waves that produce this stationary wave? [3m]

7. A ripple tank is used to demonstrate refraction of plane water waves.

Waves in deep water have a wavelength of 1.2 cm and a speed of 9.6 cm/s. The wavelength of the waves in shallow water is 0.8 cm. What is the speed of the waves in the shallow water?

[2m]

8. What causes the fuse to blow in a mains electrical circuit? [1m]

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9. The potential divider shown is connected across a constant 12 V supply.

When R has a value of 20 Ω, the voltmeter readings are equal. How do these readings change when the value of R is reduced to 10 Ω

Use the words INCREASES, DECCREASES or UNCHANGED

V1………………………………………………………………………………………….

V2………………………………………………………………………………………….

10. A double slit is illuminated normally with coherent light. The interference pattern is observed on a screen. The apparatus is shown below.

The width of both slits in the double slit arrangement is increased without altering the separation s.

not to scale

coherent light

s

screen

Describe and explain the effect, if any, of this change on

The number of fringes observed;

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(2)

(Total 2 marks)

11. Explain why a cooling system is needed near the anode of an X-ray tube.

.........................................................................................................................................................................................

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[2]

12. What must be done to an intrinsic semiconductor to turn it into a "P-type" semiconductor?

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[2m]

13. When the isotope aluminium-27 is bombarded with alpha particles, the following nuclear reaction can take place

What is the proton number and nucleon number of X?

Proton number ……………………………………….

Nucleon number…………………………………………….

[2m]

neutron.XAlHe 2713

42

SECTION B (55 Marks)

Answer all questions in the spaces provided

14. The diagram below shows two parallel conducting plates connected to a variable voltage supply. The plates are of equal areas and are a distance d apart.

The charge Q on one of the plates is measured for different values of the potential difference V applied between the plates. The values obtained are shown in the table below. Uncertainties in the data are not included.

V / V Q / nC

10.0 30

20.0 80

30.0 100

40.0 160

50.0 180

(a) Plot a graph of V (x-axis) against Q (y-axis).

Vdvariable voltage supply

+

–

(4)

(b) Draw the line of best fit for the data points. (1)

(c) Determine the gradient of your best-fit line. (2)

.....................................................................................

.....................................................................................

(d) The gradient of the graph is a property of the two plates and is known as

capacitance. Deduce the units of capacitance.

..................................................................................... (1)

The relationship between Q and V for this arrangement is given by the expression

Q =

Vd

A0ε

where A is the area of one of the plates.

In this particular experiment A = 0.20 m2 and d = 0.50 mm.

(e) Use your answer to (c) to determine a value for ε0.

.....................................................................................

.....................................................................................

.....................................................................................

..................................................................................... (3)

(Total 11 marks)

15. (a) The diagram shows a small object O represented by an arrow placed in front of a converging lens L. The focal points of the lens are labelled F.

(i) Define the focal point of a converging lens.

.....................................................................................

.....................................................................................

..................................................................................... (2)

F FO

L

(ii) On the diagram above, draw rays to locate the position of the image of the object formed by the lens.

(3)

(iii) Explain whether the image is real or virtual.

.....................................................................................

..................................................................................... (1)

(b) A convex lens of focal length 6.25 cm is used to view an ant of length 0.80 cm that

is crawling on a table. The lens is held 5.0 cm above the table.

(i) Calculate the distance of the image from the lens.

.....................................................................................

.....................................................................................

..................................................................................... (2)

(ii) Calculate the length of the image of the ant.

.....................................................................................

.....................................................................................

.....................................................................................

..................................................................................... (2)

(Total 10 marks)

16. The figure below shows a rotating magnet in an alternating current generator that is used to power a lamp.

(a) (i) State how an alternating current differs from a direct current.

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[1]

(ii) Explain, in detail, how alternating current is produced by the apparatus shown in Figure above.

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[4]

(iii) State two ways in which the current in the lamp may be increased.

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[2]

(b) The generators at a power station produce a voltage of 25 000 V. This voltage is stepped up to

400 000 V by a transformer for long-distance transmission on overhead power lines. The voltage is later stepped down to 240 V. (i) State and explain why the voltage is stepped up for long-distance transmission.

.........................................................................................................................................................................................

.........................................................................................................................................................................................

[2] (ii) Calculate the ratio of the number of turns in the primary coil of the step-up transformer to the number of turns in its secondary coil.

ratio = .......................................................... [1]

(iii) State one advantage and one disadvantage of using thicker wire in the overhead power lines. Advantage:

.........................................................................................................................................................................................

.........................................................................................................................................................................................

Disadvantage:

.........................................................................................................................................................................................

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[2] (iv) An electric drill of power 1000 W is used in a country where the mains voltage is 240 V. State and explain the most appropriate fuse to use with this drill. You should select a fuse from the following values: 1 A, 3 A, 4 A, 13 A.

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[3]

[Total 5m]

17. A cathode-ray oscilloscope (c.r.o.) is used to investigate the circuit of Fig. 4.1.

Fig. 4.2 shows the trace on the oscilloscope screen together with the time-base and y-gain (voltage)

settings when the oscilloscope is connected across AD.

(a) (i) Calculate the peak voltage (amplitude) across AD.

Peak voltage = ............................. V [2]

(ii) Calculate the peak current in the 10 Ω resistor.

current = ............................... [2] (iii) The primary (input) coil of the transformer has 30 turns and the secondary has 20 turns. Calculate the peak input voltage supplied to the transformer.

Write down the equation that you use and show all your working.

voltage supplied = ..........................V [3]

(iv) Calculate the time taken for one complete cycle of the a.c. supply.

time for one cycle = ........................... [3]

(b) (i) Name the component labelled E in Fig. 4.1.

........................................................................................... [1]

(ii) On Fig. 4.3, draw the trace that would be seen if the c.r.o. were connected across BC.

[1m]

[Total 12m]

18. The apparatus shown below may be used to investigate the photoelectric effect.

The potential difference V applied between the metal plate and electrode may be varied in magnitude and in direction. This is repeated for different values of intensity for the same frequency of light.

(a) Monochromatic light is incident on the metal plate. The potential difference between the plate and the electrode is adjusted so that the reading on the microammeter is

a maximum. The graph below shows the variation with intensity of the monochromatic light of the maximum current.

monochromatic incident light

window

vacuum electrode

metal plate

A

V

maximum current

00 intensity

Explain the features of this graph.

.........................................................................................................................................................................................

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(4)

(b) The frequency and the intensity of the light are held constant. The graph below

shows the variation with the potential difference V of the current I measured on the microammeter.

The frequency of the light is doubled at a constant intensity. On the graph above, draw a second line to show the variation with potential difference of the current in the microammeter.

(3) (Total 7 marks)

I

0–V0 0 V