Download 2013 kcse westlands

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231/2
PHYSICS (THEORY)
PAPER 2
JULY/AUGUST 2013
Time:
2 1/4 HOURS
WESTLANDS DISTRICT SCHOOLS JOINT EXAMINATION
KENYA CERTIFICATE OF SECONDARY EDUCATION
PHYSICS
Paper 2
Time 2 ½ Hours
INSTRUCTIONS TO CANDIDATES
1) Write your name and index number in the spaces provided above
2) Sign and write the date of the examination m the spaces provided above.
3) This paper consist of sections: A and B.
4) Answer all the questions in sections A and B in the spaces provided.
5) All working must be clearly shown.
6) Mathematical tables and silent electronic calculators may be used.
FOR EXAMINER’S USE ONLY
Section
A
B
Question
1-12
13
14
15
16
17
-
Total Score
Candidates should check the questions paper to ascertain that all the pages are printed as indicated and no
questions are missing.
The figure 1 below shows an. incident ray at an angle of 30° to the mirror.
incident
ray
In the circuit diagram shown below. the ammeter has negligible resistance. When the switch S is closed the
ammeter reads 0.1 A,
E=i.sv •
Determine the internal resistance of the cell.
'
(3mks)
The Table below shows regions of the electromagnetic spectrum. D is the region of visible lignt. Fill in the table if the
arrangement is in the order of increasing wavelength.
A
B
e
D
i
E
E
G
Visible light
(2mks)
An electric heater is made of a wire of resistor 100 ohms and connected to a 240V mains supply. Determine the
cost of using the heater for two hours a day for 30 days. (Given KPLC charges Ksh 5.00 per unit)
(Sinks)
A radioactive isotope of copper decays to an isotope of zinc as shown below.
69
29
Cu -------------: ----------
69
Zn
+ Radiation.
30
Name the radiation emitted and give a reason for your answer.
(2mks)
7. The figure (III) below shows a loop of a conductor with a section XY in a magnetic field.
X
When current is flowing through XY the conductor experiences a force. Indicate in the diagram the direction of the
force.
(lmk)
8.
A convex mirror of focal length 21cm produces an image on its axis, 7cm away from the mirror. Calculate the
position of the object.
(2mks)
9.
In an x-ray tube the target metal is usually tungsten. State, with reason the property that makes it suitable as a
target metal.
(2mks)
10. In the set up below the metal bar is made of steel and soft iron pieces joined together end to end.
You are provided with two iron nails. Explain how you would use the two nails to determine which side is iron.
(lmk)
11. The figure below shows a ray of light incident on the surface AC or a right-angled glass prism ABC at right angle.
The critical angle of glass is 42°. Complete the diagram to show the path of the ray until it leaves the prism. (Indicate
angles).
(2mks)
ii) the height of the image on the screen.
(lmk)
12. A convex lens is used to project the image of an illuminated slide of height 10mm onto a screen placed 2m from the
lens. The slide must be placed 400mm from the lens to give a clear image on the screen. Calculate the focal length of
the lens.
(2mks)
SECTION B MARKS)
13a) The figure below shows an electrical circuit with some quantities represented by R, I and V.
2ft
Calculate the values of:
i) I
ii) R
,
(lmk)
(lmk)
(2mks)
iii)V
b) Explain how capacitor C in the figure below is:
E
i) Charged and
(2mks)
ii) Discharged
(2mks)
The circuit diagram below shows three capacitors connected to a 20V battery.
Determine
(i) the effective capacitance.
(2mks)
(ii)
(2mks)
The total charge stored by the capacitors.
14a) A north pole of a magnet is plunged into a coil as shown in the figure below.
N
i) Indicate on the diagram the direction of the induced current.
(lmk)
(lmk)
State the effect on the induced current if (I) the turns of the coil are brought closer.
(II) the number of the turns of the coil are increased.
(lmk)
b) Transformer uses AC and not DC. Explain
c)
(lmk)
A 12V, 60w heater can be operated by a 240V mains supply transformer with 10 000 primary turns. If the
transformer is 100% efficient. Calculate
(I) The number of secondary turns.
(2mks)
(II) Current flowing in the primary coil.
(lmk)
d) State two energy losses in a transformer and their correction.
(2mks)
15a)Define the terms as used in semiconductors and diodes
(lmk)
(i) Doping
(lmk)
(ii) Rectification
b) The figure below shows an incomplete full wave rectification circuit. Complete the figure and sketch the waveform as seen
on the -C.R.O screen.
(3mks)
CRO screen
c) Iii an experiment on photo electric emission for a cleansed calcium surface, the following results were obtained.
.
SiooBiiifj potent^
-0.S
f
14
t.B
2.2
23
Lioht fmriuwicv ,;t
.5
7
0
O':
3
TO
n
interval V„ (y-axis) against frequency on the grid provided.
Plot a graph of
(5 marks)
H+F
(lmk)
II) Use your graph to determine the threshold frequency.
(3mks)
iii) Determine the gradient of the graph hence deduce a value of plancks constant.
16. The figure below shows main components of a cathode ray oscilloscope. Use it to answer the questions that
follow.
a) Name the part labelled
(I)P
(lmk)
(H)R
M
(lmk)
b) i) Explain how a bright spot is produced on the screen cathode ray oscilloscope.
(2mks)
ii)
.
State and explain the function of the grid.
(2mks)
iii) State two functions of the part labelled M.
(2mks)
c) In the space provided below sketch what would be observed on the screen if AC voltages of the same frequency are
connected across pairs of R plates and pairs of N plates.
(Imks)
17. A radioactive source, Aluminium plate' and suitable detector were arranged as below.
□
source
thick
detector
i)
Before the source was introduced, the detector registered a reading of.40 counts per second. Explain the observation.
(lmk)
ii)
Name the type of radiation emitted in the arrangement.
•
(lmk) b) A
rock sample in research station was studied and the graph of count rate against time plotted.
TIME IN MINUTES
Use the graph to determine the half-life of the radioactivity of the rock sample. '
17c) i) Distinguish between transverse and longitudinal waves.
(4mks)
(lmk)
ii) The figure below shows the displacement of a particle in a progressive wave moving from deep to shallow region in
a ripple tank.
(I) Complete the diagram to show what is observed after the boundary.
(II) Explain the above observation in (I) above.
(lmk)
(lmk)
d) The graphs in the figure below represents the same wave.
*
Determine the velocity of the wave.
(2mk)