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Bomet/Chepalungu Districts Mock- Electricity Paper 1 Question Paper

Bomet/Chepalungu Districts Mock- Electricity Paper 1

Course:Secondary Level

Exam Year:2010

NAME:…………………………………………………INDEX…………….……..…..DATE……
SCHOOL:……………………………………………..…………SIGNATURE……………………
448/1
ELECTRICITY
PAPER 1
JULY / AUGUST, 2010
2 ½ HOURS
BOMET/CHEPALUNGU SECONDARY SCHOOLS’
M-CATS
Kenya Certificate of Secondary Education 2010
448/1
ELECTRICITY
PAPER 1
JULY / AUGUST 2010
2 ½ HOURS
INSTRUCTIONS TO CANDIDATES
Candidates should have the following materials for this examination:–
– answer booklet
– drawing instruments
– mathematical tables
– drawing paper size A3
This paper has TWO sections:– A and B
Answer ALL the questions from in section A and any FOUR questions from
section B
All dimensions are in millimeters unless otherwise stated.
SECTION A: (52 marks)
Answer ALL the questions in this section.
1. a) Name four electrical related trades offered by technical institutions at craft
level. (2mks)
b) State three safety precautions to be observed when (3mks)
i). Drilling a work piece using an electric drill
ii) Handling corrosive materials.
2. Outline the procedure of measuring the resistance of a component in a live circuit
using an ohmmeter. (3mks)
3. a) State two advantages of rotating field alternator over rotating armature
alternator (2mks)
b) i). State one characteristic of each of the following dc motors:
Shunt wound
Series wound.
ii). List two applications of each of the motors in b i). above. (4mks)
4. a) Name three parts of a lead acid battery and state the function of each part.
(3mks)
b) Name the four parts of an electric circuit. (2mks)
5. a) State the meaning of each of the following terms as applied in alternating
current circuits:
i). RMS value
ii).Instantaneous value
iii).Peak value
b) State two factors which determine the inductance of a coil. (2mks)
6. a) Three resistors connected in series to a 12V source draw a current of 0.15A. If
two of the resistors are 30F each, calculate the resistance of the third resistor.
(2mks)
b). In a series RL circuit, the voltage drop across the resistor is 15V and across the
inductor is 25V. Calculate the: (5mks)
i) The supply voltage
ii) Phase angle
7. a) State two advantages of pvc sheathed wiring system over metal conduit wiring
system. (2mks)
b) Name three tests that are normally carried out on an electrical installation and
in each case state the instrument used. (3mks)
8. a) Name two types of semi conductor diodes and state one application in each case.
(2mks)
b) Draw a labeled circuit diagram of a NPN transistor in common emitter
configuration. Include the biasing sources. (3mks)
9. a) State one possible cause of the following symptoms: (3mks)
i) an ohmmeter does not adjust to zero when probes are shorted.
ii) a single phase motor hums but does not run
iii) a dc power supply has poor voltage regulation.
b) Draw a diagram of dc electromagnet and show polarity (3mks)
10. Fig1 shows an isometric drawing of a block.
Sketch in first angle projection the three orthographic views of the block. (5mks)
SECTION B: (48 MKS)
ANSWER ANY FOUR QUESTIONS FROM THIS SECTION.
11. a) Explain how each of the following transformer losses occur and state how each
is minimized. (4mks)
i) Hysteresis
ii) Eddy currents.
12. a) List six main parts that make up a meter movement system. (3mks)
b) A voltmeter movement system has internal resistance of 10F and full scale
deflection current is 10 mA (9mks)
i) Determine the sensitivity of the voltmeter.
ii) Calculate the values of the multiplier resistors to enable it to measure up to
1V and up to 100 V.
iii) Draw a circuit diagram of the voltmeter.
13. a) The RMS value of an ac sine wave is 240 V. Calculate its peak value. (3mks)
c) A single phase motor delivers 10.44 kW at full load when instruments
connected at its input have the following readings: voltmeter 240 V, ammeter 85 A
and wattmeter 14.3 kW. Calculate its: (4mks)
i) Efficiency
ii) Power factor.
14. a) Draw a labeled circuit diagram of a full wave centre tapped transformer
rectifier and explain how it operates. (6mks)
b) i. Draw the graphical symbol of NPN transistor.
ii) Explain how the terminals of an NPN transistor are identified using an
ohmmeter. (3mks)
15. a) State three advantages of miniature circuit breakers over cartridge fuses
(3mks)
b) Draw a labeled diagram of a consumer control units showing all the parts. (9mks)

Bomet/Chepalungu Districts Mock- Electricity Paper 1 Question Paper

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