4. • Electrical power is transferred from generating stations to consumers
at different voltage levels.
• Electrical power can be considered just like gas or water and same
rule applies to its distribution
i.e. proper pipeline and associated valves/switches.
Introduction
5. DOMESTIC WIRING Domestic wiring may be defined as
Wiring done in domestic houses, for providing electrical power for
lighting, fans and domestic appliances with all the safety precautions
followed is called domestic wiring.
Domestic wiring
6. • Durability: Type of wiring selected should conform to standard
specifications, so that it is durable i.e. without being affected by
weather conditions, fumes etc.
• Electrical Safety: The wiring must provide safety against leakage,
shock and fire hazards for the operating personnel.
Factors Affecting The Choice Of Wiring
7. • Appearance: Electrical wiring should give an aesthetic appeal to the
interiors.
• Cost: It should not be prohibitively expensive i.e. the system chosen
should depend upon the type of building and the purpose for which it
is used, keeping economy in view.
Factors Affecting The Choice Of Wiring
8. • Accessibility: The switches and plug points provided should be accessible and
there must be provision for further extension of the wiring system, if
necessary.
• Maintenance Cost: The maintenance cost should be minimum.
• Mechanical Safety: The wiring must be protected against any mechanical
damage.
Factors Affecting The Choice Of Wiring
10. • Parallel Wiring
The wiring for most homes is parallel, meaning several devices are
powered on a single circuit.
Both the hot and neutral wires run through the various housing boxes
along the route and branch off to individual fixtures and receptacles.
Types of wiring
11. • switch wiring
Switches, which are installed on hot wires, allow or disallow the flow of
current to a light or other device.
A knife-blade switch (shown at right) illustrates the position of the switch
when it completes a circuit, allowing electricity to power a device. The
illustration below it shows the position of the switch when it interrupts the
flow of current from the hot bus bar, disallowing the flow of electricity.
Types of wiring
12. • Series Wiring
This type of wiring is rarely used because it operates the same as old-
style Christmas lights—when one light burned out, none would
illuminate.
Series wiring routes the hot wire through several devices and then
joins the neutral wire, which leads back to the source.
Types of wiring
14. • The electricity from the mains is supplied to the houses using a three-
core wiring. They are
The Live wire
The neutral wire and
The earth wire
DOMESTIC ELECTRIC CIRCUITS
15. • Live Wire: It is at a high potential of 220 volts. The live wire has red insulation
• Neutral wire: It is at the ground potential of zero volt. The neutral wire has
black insulation covering.From the electric pole situated in our street, two
insulated wires L and N come to our house. In India, the potential difference
between the two wire is 220V.
• The Earth wire: It is a safety measure and does not affect the supply in any
way. The green earth wire is connected to a metal plate deep in the earth.
DOMESTIC ELECTRIC CIRCUITS
16. • Earthing of an electrical appliance means connecting the metallic
body of the powered appliance to the earth through the earth wire.
• It is a safety measure which ensures any leakage of current to the
metallic body of the appliance.
• This is done by keeping the potential of metallic body equal to that of
the earth (zero volt) and the user may not get a severe electric shock
by means of a metal wire called “earth wire”.
DOMESTIC ELECTRIC CIRCUITS
17. • If due to defective or damage wiring, the live and neutral wires come
in direct contact, the resistance of the circuit becomes almost zero
and an extremely large current flows through the circuit. This is called
short circuiting.
• Appliances can be protected from short circuiting by using an electric
fuse in live wire
SHORT CIRCUIT
18. • If the current drawn from the mains exceeds the safety limit (5 A for
domestic line and 15 A for power line), then this is known as
overloading.
• A circuit can be protected from overloading by using an electric fuse.
OVERLOADING
19. • It is a safety device to protect an electric circuit from overloading or short
circuiting.
• It is a piece of wire of a material of low melting point which is connected to the
live wire in the circuit. A fuse wire is connected in series in the electric circuits.
• When an excessive current flows, the fuse melts and the circuit is broken.
• The fuse wire must have proper thickness which depends on the maximum
current which the household wiring can safely carry.
ELECTRIC FUSE
20. • The two main organs of the human body where the magnetic field
produced is quite significant are the heart and the brain.
• The magnetism produced inside the human body (by the flow of ionic
currents) forms the basis of a technique called Magnetic Resonance
Imaging (MRI) used to obtain images (or pictures) of the internal parts
of our body.
MAGNETISM IN HUMAN BEINGS
