ICSE and CBSE class X reference notes for electrical circuits and house hold wiring

1. Prepared by
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2. Content
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 Main circuit
(3 wires-live, neutral, earth) with fuse / MCB, main switch)
 Color coding of wires.
 3-pin plug and socket; Conventional location of live, neutral
and earth points in 3 pin plugs and sockets.
 Switches
 Need for earthing
 Fuse
 Safety precautions

3. Components of Main Circuit
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4. Components of Main Circuit
 Three Wire System
1. Live(Phase) wire
2. Neutral wire
3. Earth wire
 Three pin plug and socket.
 Main Switch
 Fuse
 MCB(Miniature Circuit Breaker)
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5. Main Circuit
 The electrical company supply the electrical energy to the consumer premises
by overhead or underground cables.
 The power supplied through cable consists of three wires i.e Live(Phase) wire
Neutral wire Earth wire.
 The neutral and earth wire are at the same potential i.e at zero potential.
 The supply in the home is brought through high rating main fuse (switch) and
then through Energy meter.
 The main switch is a double pole switch which connects and disconnects the
company wires to consumer wires.
 The Energy meter is present there to measures the electricity consumed by the
consumer.
 This three wires are then connected through various MCB and different parts of
house
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6. Color Coding of three Wires
 The three core flexible cable is used
for many appliances. This cables
uses copper conductors for wires.
 Each wire is covered with rubber
insulation.
 For identification color coding are
used
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7. 3-pin plug and socket
Plug:-
• A 3-pin plug consists of three pins
• The 3-pin plugs are designed so that
electricity can be supplied to electrical
appliances safely.
• Each wire has its own specified color,
as shown above and each pin must be
correctly connected to the three wires
in the electrical cable.
• The plug has three metallic brass
pins.
•Normally the right side of the
consumer is live and left size is neutral.
• The top pin is more thick and longer
as compared than other two pins.
• The earth pin and neutral terminals
are directly connected to the pins but
the live terminal is connected to pin
which holds fuse.
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8. 3-pin plug and socket
Socket:-
•This device is fixed on the wall and
connected permanently to the house wiring .
•The three pin socket has three holes which
are in the form of copper tubes.
•The three pin plugs of the appliances are
inserted in this socket.
•The top hole of the socket is bigger in size
which is used to earth the fault current in
case of insulation failure of appliances.
•The new sockets consist of shutter to
protect the small children's fingers to come
in direct contact with holes.
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9. Switches
 A switch is a device for making or braking of an
electric circuit . The switches are of following types:-
1. Single pole or ordinary switch
2. Two way or Staircase switch
3. Double pole switch
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10. Single pole or ordinary switch
 Single pole switch is referred as
a single pole, single throw switch.
 It is a switch that provides a secure
connection or disconnection over two
terminals.
 It is commonly used in on/off
applications such as switches for light.
It has two terminals and metal pieces
with a spring and insulated handle.
 The switch is always connected to
the live wire. Hence when switch is
OFF no current flows.
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11. Two way or Staircase
switch
•Fig shows 2-way switch wiring diagram which has been used to control
a bulb in staircase.
•The schematic shows that circuit is completed and bulb is ON.
• Suppose you want to OFF the bulb from the upper switch at top of stair
( (upper portion of staircase) ) simply Switch OFF the switch then circuit
will break and the bulb will be OFF.
• To switch ON the bulb again, just switch ON the same switch at upper
portion of staircase.
•In other words you can OFF and ON bulb from upper switch at the top
of stair. Obviously; you can perform the same operation from the bottom
switches installed in staircase.
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12. Double pole switch
•A double pole switch is
used when it is desirable to
cutoff both the lines of
electrical supply.
•It is useful in case of
safety where one cannot
identify between phase
and neutral.
•This switch is used as the
main switch in household
wiring.
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13. Fuses
 It is a short length of wire put in electrical circuit for
protection purpose.
 It is made up of alloy of lead and tin(63% tin and
37% lead)
 It has a high resistivity and low melting point.
 When fault occurs, the current exceeds the limit of
current and the fuse blows out and the circuits gets
cutoff.
 The fuses are used for the safety of the person and
building.
 Hence used in electrical gadget to protect the gadget
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14. Fuse Rating
 The fuse rating is the maximum safe current
permitted to flow in a fuse before it blows out.
 For lighting circuit the fuse rating used is of 5A.
 For power circuit the fuse rating used is of 10A to
15A.
 Fuses Blows due to
1. Short Circuit
2. Overloading of electrical circuit.
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15. Types of Fuses
Kit Kat Fuse
Cartridge Fuse
HRC Fuse
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16. Earthing
•Earthing is the process of
connecting non conducting
metallic body of electrical
appliance to a large conducting
body like earth.
•A large metal plate is burried
under earth depth where the
soil is moist.
•The metallic plate is
surrounded with mixture of
charcoal and salt to ensure
good contact with wet soil.
•The metallic body of power
appliance in home such as
heater, gyser, electric iron, etc
are provided with earthing.

17. Need of Earthing
•The earthing protects the personnel from the shortcircuit
current.
•The earthing provides the easiest path to the flow of shortcircuit
current even after the failure of the insulation.
•The earthing protects the apparatus and personnel from the
high voltage surges and lightning discharge.
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18. Safety Measures in using
Electricity
 Use wire of high quality and good insulating
material.
 Cover all naked wire and and joints with
insulating tape.
 Make all connections tight
 Never touch any part of electrical circuit without
rubber shoes.
 Use Fuse of proper rating.
 Connect switches and fuses for live wire.
 Due not use water as fire extinguisher in case of
fire due to electricity.
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