Simple electrical wiring

An electric is a complete path through which electrons or current flows. The path is made up of cable or wire which connect all the components of the circuit.

Components of an electric circuit include:

(i) Battery or generator: This is referred to as the power source.

(ii) Conductor: This is the cable or wire used in connecting other components. The conductor is made of copper.

(iii) Load: This includes the lamp and the other electrical appliances connected to the circuit e.g. radio and T.V. sets, fan, etc.

(iv) Control: This refers to the electric component that is used to switch “on” and “off” current. Fuses are included as control since they cut off in case of excess voltage.

V = voltage, I = current, and R = Resistance

Mathematical relationship between voltage, current and resistance is expressed as follows

V = IR, I = V/R and R = V/I

Example:

(i) A current of 0.5A flows in a circuit with resistance 60 ohms. Calculate the potential difference within the circuit.

Solution

(i) V = IR

Current (I) = 0.5A, Resistance (R) = 60Ω

Voltage (V) = 0.5 x 60 = 30 volts

Wiring Tools and Materials

Hand tools used in the process of electrical installations are referred to as wiring tools. They are common tools such as pliers, hammer, screwdrivers, small knives, punches, cutters, hand gloves e.t.c. Wiring materials includes, black sole tape, clips, wooden block, cable, screws, etc.

Uses of Wiring Tools and Materials

Pliers: These are used in holding, cutting and joining conductor or cables. The pliers are coated or insulated with rubber materials.

Hammer: It is a tool used to drive in nails inside the walls to hold some of the wiring accessories such as wooden blocks. Clips are held on the walls with nails driven in the hammer.

Screwdriver: This is specially used to drive screw nails inside the socket and lamp holders to fasten them on the wooden block. Most screwdriver used in wiring (electrical installation) are equally used as testers i.e. used to determine the presence of current in the live cable. There are three types: Star, flat and ratchet screw drivers.

Small knives are used to peel the rubber coatings of the cable for joining. Punches are used to make holes on walls to allow the passage of the cables from one apartment to another.

Cutters are used to cut the wires where necessary.

Hand gloves are used to protect the hand from electric shock etc.

Black sole tapes are used to cover exposed conductors.

Metal clips are used to hold the cables firm on the walls while the screws hold the lamp holders etc.

Wiring Accessories

An electrical accessory is any device other than luminaries (lighting fittings) associated with the wiring and current utilizing appliances of an installation. Examples of electrical accessories include: tumbler switches, lamp holders, ceiling switches, ceiling roses, joint boxes, fuse boxes, socket outlets/plugs, lamp holder, adaptors, connector, etc.

Accessories are related for the maximum voltage, and in some cases rated for the maximum current they are designed to withstand without undue overheating or failure. Some accessories are coated or covered with protective substance to make them suitable for a particular or various possible environment hazards.

The consumer’s equipment begins with the main switch gear, fuse box or consumer unit to which the accessories are connected through surface or embedded wiring systems for lighting and power points. All socket outlets have their earth terminals connected to the consumer’s so that appliances and consumers are protected against dangerous earth leakage by the use of the three-pin plug which allows connection to earth.

Wiring circuit for lightening and power points: In simple electric wiring, two electric circuits are observed: series circuit and parallel circuits.

Generally, all house wiring is done so that points of lights are connected in parallel, except for special cases like ceremonial lightings, photo studios and dark rooms which utilize series of lighting for increased brightness. Each circuit has its beginning connected to the fuse-way in the fuse box or splitter unit, then to a switch then separately to switches ; or looped by switch feeds then to the lamp holders or lighting fittings (through the lamp feed0 and back to the neutral terminal of the fuse box (through the neutral conductor). Multi-core cables e.g. twin or three core- insulated and sheathed cables are used on surface wiring in connection with joint boxes, but single insulated core cables are used in conduit to permit easy branching with less jointing; however the basic circuits are the same.

Assessment

A current of 0.8A flows in a circuit with resistance 80 ohms. Calculate the potential difference within the circuit.