# Physics Paper 2 Questions - Kapsabet Boys Post Mock 2023 Exams

INSTRUCTIONS

• This paper consists of TWO sections: A and B.
• ALL working MUST be clearly shown.
• Non-programmable silent electronic calculators and KNEC mathematical tables may be used.

## QUESTIONS

Section A (25 marks)
Answer all Questions in This section Turn over

1. Locate the position of the image of the object placed in front of a plane mirror shown below. (2 marks)
2. Show the magnetic field pattern of the current carrying conductors shown below. (2 marks)
3. A student uses this apparatus to investigate what happens to a current-carrying conductor in a magnetic field. The student connects the two parallel horizontal metal rails to the positive and negative terminals of a power supply. The metal rod AB rests across the rails and is free to move.

Explain what happens to the metal rod AB. (2 marks)
4. State two advantages of using a convex mirror as a driving mirror. (2 marks)
5. State two factors that affects the resistivity of an electrical conductor. (2 marks)
6. The figure below shows a wave in progress.

Determine the
1.  Amplitude (1 mark)
2. Frequency (2 marks)
7. The photograph shows the apparatus the student has available.

Describe briefly how the student should carry out the experiment. (4marks) You should include:
• What the student should measure
• How the measurements should be made
• How the student should use a graph to find the refractive index.
8. A current ,I, flowing through a wire of resistance ,R, is increased by seven times. Determine the factor by which the rate of heat production was increased. (3marks)
9. The wavelength of a radio wave is 1km. Determine its frequency if the speed in 3 x 108ms-1 (2marks)
10. State two uses of gold leaf electroscope. (2marks)
11. Give a reason why soft iron is used as a core of the coil of an electric bell. (1mark)
12. State two differences between pinhole camera and the human eye. (2marks)
13. The figure below shows a transformer connecting an overhead 25 000 V electrical power line to a house.

1. State whether coil A or coil B in the transformer has the larger number of turns (1 mark)

SECTION B (55 MARKS)
Answer all the questions in this section

1.
1. Explain what is meant by the principle of superposition of two waves. (2marks)
2.  In an experiment to try to produce an observable interference pattern, two monochromatic light sources, S1 and S2, are placed in front of a screen, as shown in Fig.1.

1.  In order to produce a clear interference pattern on the screen, the light sources must be coherent.
State what is meant by coherent. (1mark)
2.  In Fig 1, the central point O is a point of maximum intensity. Point P is the position of minimum intensity nearest to O. State, in terms of the wavelength λ, the magnitude of the path difference S1P and
S2P. (2marks)
2.  An X-ray tube is operated at 120Kv with a beam current of 0.5mA. Assuming its efficiency is 1%, calculate:
1. The number of electrons hitting the target each second (3marks)
2. The X-ray energy emitted each second (2marks)
3. The heat energy dissipated (2marks)
4. The minimum wavelength of the emitted X-radiation. (2marks)
3. In an experiment to determine the range of beta particles in aluminium, different thickness of aluminium sheets were interposed between a small beta source and the window of a Geiger tube 20mm apart.
 Thickness/mm 0 0.45 0.9 1.35 1.8 5.4 7.2 Count rate/s-1 85 59.5 41.6 29.2 20.4 1.5 1.5

1. Plot a graph of count rate against thickness. (5mks)
2. Use your graph to determine the range of beta particles in aluminium . (2marks)
3. The diagram shows an uncontrolled nuclear fission reaction. When a slow-moving neutron strikes an atom of U, the atom splits. In this reaction two fast moving neutrons are produced together with the radioactive fission fragments of Ba (barium) and Kr (krypton).

1. What name is given to an uncontrolled fission reaction? (1mark)
2. Complete the nuclear equation for this reaction. (2marks)
23592 U + 10n→144Ba+36Kr+210n
3. In a nuclear reactor, the fission reaction is controlled using control rods of boron steel which readily absorb neutrons and a graphite moderator which improves the chances of uranium atoms splitting apart. State how the graphite moderator improves the possibility of fission of uranium. (1mark)
1. Explain how the energy released from a nuclear reactor can be increased. (2marks)
2. Outline the advantages of producing electricity from nuclear fusion rather than nuclear fission in the future. (2marks)
4. Explain what is meant by the half-life of a radioactive substance. (1mark)
5. The count rate changed in the way shown in the graph below:

Use the graph to find a value for the half-life of the radioactive source. (2marks)
4. A set of Christmas tree lights consists of 40 identical filament lamps connected in series across a supply of 240V.
1. Define resistance. (3marks)
2. Each lamp when lit normally carries a current of 250mA. Calculate:
1. The potential difference V across a lamp. (3marks)
2. The resistance R of a lamp. (3marks)
3. The circuit shown is used to investigate how the current changes with voltage for component Z
.
1. Name the component: (3mks)
X ………………………………………………………………………………………
Y ……………………………………………………………………………………
Z ………………………………………………………………………………………
2. The results from the investigation are shown on the graph.

1. Describe carefully how the current through Z changes as the voltage is increased from 0·0 to 0·7V. (2marks)
2. Write down in words an equation and use it to find the resistance of Z when the voltage is 0·7V. (2marks)
5. Figure below shows two capacitors, A of capacitance 2μF, and B of capacitance 4μF, connected in parallel. Fig. 2.2 shows them connected in series. A two-way switch S can connect the capacitors either to a d.c. supply, of e.m.f. 6V, or to a voltmeter.

1. Calculate the total capacitance of the capacitors
1. When connected as in Fig. 2.1 (2marks)
2. When connected as in Fig. 2.2 (2marks)
2. The switch in the circuit shown in Fig. 2.1 is then connected to the battery. Calculate
1. The potential difference across capacitor (2marks)
2. The total charge stored on the capacitors. (2marks)
3. The switch in the circuit shown in figure above is then connected to the battery. Calculate the total energy stored in the two capacitors. (2marks)

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