KNEC Physics Paper 2 Question Paper / 2016 KCSE MOKASA Joint Examination

Figure 1 show a ray of light incident on a plane mirror.

(a) On the diagram, indicate the direction of the reflected ray. (1mark)
(b) Give reason for the path shown above. (1mark)

State what happens to the image when one moves closer to the object when using a
pinhole camera.

An object of height 2 cm is placed 25 cm in front of a concave mirror. A real image is
formed 75 cm from the mirror. Calculate the height of the image.

State the law of magnetism.

State and explain the functions of the keeper when storing magnets.

Figure 2 shows a steel bar to be magnetized.

Complete the circuit such that both poles P and Q acquire opposite polarity (North- south
respectively).

Figure 3 shows a set up of a simple cell.

(a) Name the electrode A and electrolyte B. (2marks)
A:
B:
(b) State two reasons why the bulb goes off a short time. (2marks)

(c) Give one method of minimizing the defect that occurs in plate A. (1mark)

The chart below shows part of the electromagnetic spectrum.

(a) Identify the radiation marked A and C. (1mark)
A:
C:
(b) Give one application of the radiation marked B. (1mark)

The range of audible frequencies varies from 20 Hz to 20 kHz. If the speed of sound is
340 m/s, what is the corresponding range of wavelength?

Distinguish between transverse waves and longitudinal waves.

Figure 4 shows a wave form

Determine the wavelength given that the speed of the wave is 400 m/s.

An electric kettle is rated at 1.8 kW, 240 V. Explain the choice of the safest fuse for the
kettle. (the available fuses are 5 A, 10 A, and 20 A)

(a) A bar magnet is pushed into a coil as shown in Figure 5 below.

Explain what happens to the pointer of the galvanometer when the magnet is:
(i) Moved into the coil rapidly? (1mark)
(ii) Remains stationary inside the coil? (1mark)
(b) State two ways of increasing the magnitude of induced current in a generator. (2marks)
(c) A transformer has 200 turns in the primary coil and 1000 turns in the secondary coil. The
primary coil is connected to an a.c source producing 100 V and rated 500 W. The current
delivered by the secondary circuit was found to be 0.95 A.
(i) Determine the efficiency of this transformer. (3marks)
(ii) Explain why the efficiency is less than 100%. (2marks)

(a) A coin is placed at the bottom of a tall jar. The jar is filled with paraffin to a depth of
32.4 cm and the coin is apparently seen displaced 9.9 cm from the bottom. Determine the
refractive index of air with respect to paraffin. (3marks)
(b) Define the term critical angle. (1mark)
(c) Figure 6 shows a ray of light passing through a glass prism.

If the speed of light in prism is 2.0 x 10⁸m/s
(i) Determine the refractive index of the prism material given that the speed of light
in air is 3.0 x 10⁸m/s. (2marks)
(ii) Determine the value of the critical angle c and show it on Figure 6. (2marks)

(a) Differentiate between an Ohmic and non-ohmic conductor giving one example in
each case. (2marks)
(b) Figure 7 shows a circuit with resistors and voltmeter connected to a battery.

(i) If each cell has an internal resistance of 0.7Ω, determine the total resistance in the
circuit. (3marks)
(ii) What amount of current flows through the 3Ω resistor when the switch is closed?
(3marks)
(iii) What is the reading of the voltmeter when the switch S is
(I) Open (1mark)

(II) Closed (1mark)
(iv) Account for the difference between the answers in (I) and (II) above. (1mark)

Figure 8 shows an electromagnetic relay being used to switch an electric motor on and
off. The electromagnet consists of a coil of wire wrapped around a core. The motor in
figure is switched off.

(a) Suggest suitable material for the core. (1mark)
(b) What happens to the core when switch S is closed? (2marks)
(c) Why do the contacts A and B close when the switch S is closed. (2marks)
(d) When the switch S is opened, what will happen to;
(i) The core (1mark)

(ii) Soft iron armature. (1mark)
(e) Give one other application of an electromagnet. (1mark)
(f) State two ways in which an electromagnet could be made more powerful. (2marks)

(a) Give a reason why a candle flame is blown when a highly charged conductor is
brought close to it as shown in Figure 9. (2marks)

(b) Figure10 shows 1μF, 2μF, 4μF and 5μF capacitors connected to a battery.

Determine:
(i) The total capacitance. (2marks)
(ii) The total charge. (2marks)
(iii) Voltage across the 4μF capacitor. (2marks)

(a) In an experiment to observe interference of light a double slit experiment was placed
close to the monochromatic source as shown in Figure 11.

(i) State the function of the double slit. (1mark)
(ii) Describe what is observed on the screen. (2marks)
(b) Figure 12 shows an object O placed in front of a diverging lens whose principal focus is
F.

On the diagram, draw rays diagram to locate the image formed. (3marks)

(c) Figure 13 shows a defective eye focusing a distant object.

(i) Name the defect. (1mark)
(ii) On the same diagram, sketch the appropriate lens to correct the defect and sketch the
rays to show the effect of the lens. (2marks)