Exp.No:3
WIRES, CABLES, SWITCHES AND FUSES
OBJECTIVE
To identify different types of wires, cables, switches, fuses and their uses.
THEORY
Electrical Wires and Cables
In electrical house wiring, it is difficult to differentiate between wire and cable as
these are used more or less synonymously. Single wire which may be bare or covered
with insulation is known as wire. Several wires with insulation and stranded together
is known as cable. The cable consists of three parts:
1. Conductor or core – Aluminium or copper wire
2. Insulation – to cover aluminium or copper
3. Protective covering – to cover insulation for protection against mechanical
damage or moisture.
Conductor Material
The principal materials used to produce electrical conductors are the copper and
aluminum. The copper is mechanically strong, durable and ductile. It is highly
resistive to corrosion and oxidation. It can withstand high temperature and dampness.
The copper being costly material, is used for power distribution for long distances.
The aluminium being light and not so strong, it is used for transmission line
conductors reinforced by steel wires.
Insulating Material
The insulation of cable should have high resistance, dielectric strength, capacity to
withstand high temperature, mechanical strength and should be non-inflammable.
Various types of insulating materials used in cables are: rubber, Vulcanised Indian
Rubber(VIR), Paper, Poly-vinyl Chloride(PVC), Vulcanised Bitumen, Cotton and
Silk, Gutta-Percha, Enamel Insulation and Varnished Cambric.
1
, Wire Gauge
The wire gauge, the measurement of wire diameter, determines the amount of
current that a wire can carry safely as well as its electrical resistance and weight.
Generally larger guage numbers are used to represent the smaller wire diameter. A
standard wire guage tool is shown below.
Types of Wires Used for Internal Wiring
The wires used in domestic installation can be divided into the following:
1. V.I.R. Wires – Vulcanised Indian Rubber Wires have only single braid of
rubber of 250 volts grade. Such wires are used in ordinary electrical wiring.
2. P.V.C. Insulated Wires – Poly-vinyl Chloride insulated wires have more
insulating qualities. These wires are used in concealed conduit wiring system
3. T.R.S. or C.T.S. Wires – Tough Rubber Sheathed or Cab Type Sheathed wires
are provided with a tough rubber compound which does not deteriote even
after long exposure to moisture.
4. Lead Alloy Sheathed Wires – The ordinary wires are covered with a
continuous sheath of lead . They provide complete resistance to moisture and
are recommended where climatic conditions are not dry.
5. Weather Proof Cables – These cables are used for outdoor wiring and
underground duty. The insulate individual wires are formed together (to make
it 3core or 4 core) suitably taped together, braided and then compounded with
weather resisting material.
2
WIRES, CABLES, SWITCHES AND FUSES
OBJECTIVE
To identify different types of wires, cables, switches, fuses and their uses.
THEORY
Electrical Wires and Cables
In electrical house wiring, it is difficult to differentiate between wire and cable as
these are used more or less synonymously. Single wire which may be bare or covered
with insulation is known as wire. Several wires with insulation and stranded together
is known as cable. The cable consists of three parts:
1. Conductor or core – Aluminium or copper wire
2. Insulation – to cover aluminium or copper
3. Protective covering – to cover insulation for protection against mechanical
damage or moisture.
Conductor Material
The principal materials used to produce electrical conductors are the copper and
aluminum. The copper is mechanically strong, durable and ductile. It is highly
resistive to corrosion and oxidation. It can withstand high temperature and dampness.
The copper being costly material, is used for power distribution for long distances.
The aluminium being light and not so strong, it is used for transmission line
conductors reinforced by steel wires.
Insulating Material
The insulation of cable should have high resistance, dielectric strength, capacity to
withstand high temperature, mechanical strength and should be non-inflammable.
Various types of insulating materials used in cables are: rubber, Vulcanised Indian
Rubber(VIR), Paper, Poly-vinyl Chloride(PVC), Vulcanised Bitumen, Cotton and
Silk, Gutta-Percha, Enamel Insulation and Varnished Cambric.
1
, Wire Gauge
The wire gauge, the measurement of wire diameter, determines the amount of
current that a wire can carry safely as well as its electrical resistance and weight.
Generally larger guage numbers are used to represent the smaller wire diameter. A
standard wire guage tool is shown below.
Types of Wires Used for Internal Wiring
The wires used in domestic installation can be divided into the following:
1. V.I.R. Wires – Vulcanised Indian Rubber Wires have only single braid of
rubber of 250 volts grade. Such wires are used in ordinary electrical wiring.
2. P.V.C. Insulated Wires – Poly-vinyl Chloride insulated wires have more
insulating qualities. These wires are used in concealed conduit wiring system
3. T.R.S. or C.T.S. Wires – Tough Rubber Sheathed or Cab Type Sheathed wires
are provided with a tough rubber compound which does not deteriote even
after long exposure to moisture.
4. Lead Alloy Sheathed Wires – The ordinary wires are covered with a
continuous sheath of lead . They provide complete resistance to moisture and
are recommended where climatic conditions are not dry.
5. Weather Proof Cables – These cables are used for outdoor wiring and
underground duty. The insulate individual wires are formed together (to make
it 3core or 4 core) suitably taped together, braided and then compounded with
weather resisting material.
2
