Instructions to Candidates
- Write your name and index number in the spaces provided above.
- This paper consists of two sections A and B
- All working MUST be clearly be shown in the spaces provided.
- Silent non-programmable electronic calculators may be used.
- This paper consists of 12 printed pages
- Candidates should check the paper to ascertain that all the pages are printed as indicated and that no questions are missing.
- Candidates should answer the questions in English.
FOR EXAMINER'S USE ONLY
|Section||Question (s)||Max. Score||Candidates Score|
SECTION A: (25 MARKS)
Answer all the questions in this section in the spaces provided.
1. The figure below shows an object O placed infront of a plane mirror. Complete the ray diagram to show the position of image as seen by the eye E. (2 marks)
2. The figure below shows two circuits with identical cells and bulbs
State with reason, in which circuit the bulbs will be brighter (2 marks)
3. State one advantage of an alkaline accumulator over a lead-acid accumulator. (Imark)
4. The figure below shows a bar XY being magnetized.
- State the pole acquired at Y........... (1mark).
- State one disadvantage of the method of magnetisation used above. (1mark)
5. State two ways of increasing the force on the current carrying conductor in a magnetic field. (2marks)
6. An 8000W heater is used for a total of 45 minutes a day. Calculate the cost of using this shower for a month of November 2020 if the cost of an electrical unit is Ksh.7.00. (3marks)
7. The figure below shows a capacitor network.
Determine the capacitance C if the total capacitance of network is 2.4 x 10-6F (2 marks)
8. Figure 3 shows an object O placed in front of a converging mirror of focal length 15 cm.
Draw on the figure a ray diagram to locate the object. (3 marks)
9. State two factors that affect the capacitance of a parallel plate paper capacitor (2 marks)
10.State one factor that affect photoelectric emission from a given metal surface. (1 mark)
11. When a highly positively charged rod moves slowly towards a negatively charged electroscope, it is observed that the leaf divergence first decreases and then increases when the rod moves nearer to the cap. Explain. (2 marks)
12. State one reason why the Cathode ray Oscilloscope (C.R.O) is preferred in measuring voltage to the moving coil voltmeter. (1 mark)
13. The figure below shows water waves travelling from a shallow region towards a deep region. Complete the diagram (1 mark)
14. One condition necessary for total internal reflection to occur is that light must be travelling from optically denser to optically less dense medium. State the other condition. (1 mark)
SECTION A: (55 MARKS)
- State Lenz's law of electromagnetic induction. (1 mark)
- A bar magnet is moved into a coil of insulated copper wire connected to a centre-zero galvanometer as shown in figure
- Show on the diagram the direction of induced current in the coil. (1mark)
- State two ways of increasing the magnitude of induced current. (2marks)
b). The figure below shows two coils P and S wound on a soft iron core. It is connected to a 250V mains source.
- Identify the type of the transformer (1 mark)
- If P has 1000 turns while S has 600 turns and a resistance of 100Ω. Determine the maximum current measured on the ammeter if the transformer losses 20% of the input power into heat (3 marks)
c). Explain how energy losses in a transformer are minimised by having:
- A soft-iron core (2 marks)
- A laminated core. (2marks)
- Distinguish between Potential difference and the Electromotive force of a battery (1mark)
- State Ohm's law (1mark)
- The circuit set up shows two cells each of E.m.f 1.5 V and internal resistance of 20 Connected with a ammeter and resistor a network as shown
- the total resistance in the circuit (3 marks)
- the reading on the ammeter (2 mark)
- The "lost" voltage (2marks)
- The graph below shows the variation of potential difference V with current, I for a cell.
From the graph determine:
- nternal resistance of the cell. (3 marks)
- The E.m.f of the cell (1 mark)
17. Use the diagram in figure below to answer the questions that follow
- Name the parts labelled C and D (2 marks)
- The metal used in making the rotating metal target is tungsten. State the reason why iron is not used (1 mark)
- State the advantage of having a rotating anode over a fixed anode. (1mark)
- Name the parts labelled C and D (2 marks)
- Explain how X-rays are produced in such a tube (3 marks)
- Explain how
- Intensity of X-rays from such a tube may be increased (1 mark)
- Penetrating power of X-rays from such a tube may be increased. (1 mark)
- State one difference between electromagnetic waves and mechanical waves. (1 mark)
- The wave shown in figure below has a velocity of 20m/s
- amplitude of the wave (1 mark)
- the wavelength of the wave. (1 mark)
- the frequency of the wave. (2 marks)
- the periodic time of the wave. (2 marks)
- A girl standing in front of a wall 90 m away claps her hands at time intervals of 0.5 seconds. She notices that each echo produced by the wall coincides with the next lap. Determine the speed of sound. (3 marks)
- Distinguish between intrinsic and extrinsic semiconductor (1mark)
- Figure is a circuit with two lamps L, and L, and components D1 and D2
- State the observation made when switch K is closed. (1mark)
- Explain the observation made in (i) above. (2 marks)
- The figure shows a circuit used for a full wave bridge rectification.
- Insert diodes D1, D2, D3 and D4 to complete the circuit.(2marks)
- State the use of capacitor C.(1marks)
- On the axes below draw a voltage - time display of the C.R.O.(2 marks)
- State two advantages of the four diode rectifier over a two diode one. (2 marks)