Question 2
- (i) List three types of electrical tests for domestic installations.
(ii) Why is it important to conduct electrical tests in domestic installations?
(iii) Name three instruments used for conducting tests in electrical installations. [ 7 marks]
- (i) Define a.c. motors.
(ii) Give two applications of an a.c. motor.
(iii) State two differences between d.c. and a.c. motors. [6 marks ]
- (i) Draw the B.S graphical symbol for the following devices:
- Fuse;
- Circuit breaker;
- Switch gear;
- Contactor.
(ii) State three reasons for the installation of protective devices [3 marks]
- List five basic components in writing a proposal for starting up an
electrical installation business. [5 marks ]
Observation
The question was attempted by majority of the candidates and their performance was poor.
In part (a), majority of the candidates that responded to the question listed the three types of electrical tests for domestic installations.
In part (b), majority of the candidates could not give correct definition of a.c. motors and their applications.
In part (c), it was reported that candidates had poor knowledge of B.S graphical symbols.
In part (d), majority of the candidates could not list five basic components in writing a proposal for starting up an electrical business.
The expected answers include:
2.(a)(i) Types of electrical tests for domestic installations
- polarity test
- insulation resistance test
- earthing test
- continuity (ring circuit) test
(ii) Importance of electrical tests in domestic installation
- to ensure that the installation is properly done
- to detect fault
- to correct fault
- to certify that the installation is fit/ safe for use
- to prevent hazard, malfunction and breakdown of domestic
equipment/installation
(iii) Instruments for conducting test in Electrical Installation
- insulation resistance tester/megger
- bell set tester
- ohmmeter
- electrician phase tester
- testing lamp
- avometer/multimeter
- voltmeter
- testing screw driver
- ammeter
(b)(i) A.C. motor is a device which converts electrical energy into mechanical energy.
(ii) Application of A.C. motor
- water pumps
- blenders
- ceiling fans
- grinders
- air condition fans
- a.c. compressor
- drilling machine
- milling machine
(ii) Reasons for installation of protective devices
- to prevent earth leakage
- to prevent electric shock
- to prevent excess current
- to prevent low voltage
- to prevent damage by fire
- to maintain continuity of supply
- to isolate the consumer installation from the main supply
- to prevent lightening
(d) Basic components in writing a proposal for starting up an electrical installation business
- title page/cover page
- executive summary
- introduction of the project
- objectives/purpose of the project/statement of need/ideas
- scope of the project/project description
- qualification/experience
- budget/cost
- conclusion
- appendices