SECOND TERM LESSON NOTE FOR WEEK
CLASS : JSS 3
SUBJECT : BASIC TECHNOLOGY
TOPIC : SIMPLE ELECTRICAL WIRING
DURATION : 40 MINUTES
PERIOD : SINGLE PERIOD
REFERENCE BOOK :
- Basic Technology for Junior Secondary School, JSS 3
- Scheme of work for Junior Secondary School (JSS 1 – 3)
INSTRUCTIONAL MATERIAL :
LEARNING OBJECTIVES : At the end of the lesson learners will be able to
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Electrical wiring deals with how wires can be connected together in a building in order to bring light into the housing system.
Most appliances in the house are connected to the main supply (wall socket) through a three pin plug.
The main voltage supply of electricity in the house is 240volts per phase. All items of electrical equipment are connected by means of cable or other kind of inductors. The fuse box contains fuses. The function of each fuse is to prevent overloading electrical cable.
a) A Red/Brown colour insulator which is connected to the terminal Live (L)
b) A Black/Blue colour insulator which is connected to the terminal Neutral (N)
c) A Yellow/Green colour insulator which is connected to the terminal Earth (E)
The main purpose of earthen building is to prevent electric shock and this why the earth wire (Yellow/green) is introduced for safety.
Wiring the points in the house is done in parallel in order to ensure independent of electricity supply in each point. Electricity installation in a house requires the services of qualified and licensed electrician.
METHODS OF WIRING ELECTRICITY.
1) SERIES CIRCUIT WIRING METHOD.
A series circuit wiring is the one in which the same current flows from the positive terminal of the battery to the negative terminal of the battery. In this circuit wiring, all the accessories are connected end to end or back to back, this is because, the same current flows through the accessories in a series circuit connection.
Note: Two or more electrical accessories are said to be connected in a series, if the same electric current flows through them and different voltages in applied across the circuit. A fault which may occur in any of the accessories automatically stops the flow of current at that point and the whole circuit. For examples, in a television, when its tubes stop working or burns out then the television stop working
Leave 5 lines to draw the daigram of series circuit
2) PARALLEL CIRCUIT WIRING METHOD.
A parallel circuit wiring is the one in which there is more than one path through which current can flow. All conductors and electrical accessories are connected side by side so that only some electric current flow through each appliance. Two or more electrical accessories are said to be connected in parallel, if the same voltage run across all of them and different current flows through the circuit. All the accessories used in a house wiring are connected in parallel, this is because it is easy to switch-off individual accessory without affecting the operation of other accessories connected to the wiring circuit.
In this method of wiring, a fault which may occur in one distinct path of the current will not affect or stop the current flowing through the other path.
Leave 5 lines to draw the daigram of parallel circuit
WIRING TOOLS AND MATERIALS.
The tools which are used for the electrical wiring and installation of circuits in the homes, offices and other building structures can be used and reused in electrical wiring.
The electrical wiring tools include:
1) Pliers: These are used for cutting, pulling and twisting wires, skimming of insulating cover from wires.
2) Hammers: These are used for driving nails into walls, for fixing of clips, insulating wires lamp holder and so forth.
3) Screw drivers: These are used for tightening screws into the wooden blocks for holding switches, lamp holders and ceiling roses into position.
4) Testers: These are used to detect the presence of electrical points as it will glow, if there is current passing through.
5) Scrapers: These are used to open the mechanical protection of cables, where there is need to expose the wire.
6) Gimlets: These are the boring tools used to bore holes in wooden blocks before inserting or driving in screws to hold them on wall.
7) Hacksaws: These are used to cut pipes in conduit wiring or to make web in the wooden blocks.
8) Punches: These are normally used for making holes in walls of wooden blocks during wiring.
9) Small Knives: These are used to peel the rubber coating of the cables for joining.
10) Cutter: These are used to cut wires where necessary.
11) Hand gloves: These are used to protect the hand from electric shocks.
12) Black cello-tapes: These are used to cover exposed conductors.
WIRING TOOLS AND MATE7RIALS.
The electrical wiring materials: the materials which are required for electrical wiring are used only once. The main materials required in electrical wiring include:
1) Cables: These are insulated wires that provide electrical connections between electrical loads and supply points during wiring.
2) Wiring Nails: The wiring nails are driven into the wiring surface of the wall to hold the clips. The wiring nail comes in different lengths, depending on the type of clips used. For instance, copper is used to coat most wiring nails.
3) Clips: These are made of aluminium sheets. They are used to fasten electrical cables to the wall of ceiling during wiring.
4) PVC Pipes: These are the insulated pipes through which cables are passed in conduit wiring and they are buried in the wall before plastered.
5) Screw: These are used to mount accessories on the wooden blocks. There are different sizes of screws: 11/2”, 1”, ¾”, ½”, ¼”.
Presentation Steps :