1) The document discusses the safe use of electricity in the home. It describes common electrical appliances like lighting, heating, and motors. 2) It outlines electrical hazards such as damaged insulation, overheating of cables, damp conditions, and carelessness that can cause electric shock. 3) The document provides guidance on safely using electricity through the use of fuses, circuit breakers, earthing of appliances, and double insulation to protect against electric shock.

1. PRACTICAL ELECTRICITY
Uses of electricity
Dangers of electricity
Safe use of electricity at home

2. Introduction
 Electricity is widely used in the
modern world.
 In this section, we will be looking at
some common household appliances
that use electricity , the major hazards
and safe use of electricity.

3. Uses of Electricity
 Electricity is most commonly used
in electric heating, lighting and motors.

4. Electrical lighting
 When the switch is closed, current
flows through one wire to the lamp,
lights it up, and flows back through
the other wire. This completes the
circuit.

5. Electrical heating
 When the switch at the socket is on,
current flows through one wire in the
cable to the kettle. The current goes into
the kettle and heats up the water. The
current then leaves, goes through a
different wire in the cable, and return to
the other contact point on mains socket.

6. Electrical Motors
 A motor is used in the electric fan. The
electric fan normally has a cable that plugs
into the mains socket on the wall. When the
switch on the mains socket is on, current
flows through one wire in the cable, and goes
into the motor in the fan. The motor then
rotates the fan.

7. Electrical calculation
 POWER
Electrical power of an appliance is
given by the formula
power = current × voltage,
unit of power= watt(W)
VIP

8. Electrical calculation
 ENERGY
Electrical Energy of an appliance is given
by the formula
energy = power x time
= current x voltage x time
unit of energy: Joule
(J)
tVIE

9. Electrical cost calculation
Our daily household energy consumption is not a free service, that is
we have to pay a monthly bill for the electricity we used in our
houses.
In order to calculate the cost of this energy consumption, we have to
sum all the energy we used and then multiply it to the value for each
unit of electrical energy we use.
The total amount of energy consumed is recorded in the electricity
meter found in all household that has electricity.
Note: The energy consumption is recorded in kilowatt-hour (KWh)
CALCULATION of energy consumption:
Energy(E) = Power (P) x Time(t)
(kWh) (kW) (h)
CALCULATION of cost:
Cost = Energy(E) x cost of 1KWh
(Rs/$) (KWh) (Rs/$)

10. Exercises
1. A light bulb is connected to a 240 V supply. The current that
flows through it is 0.1 A. What is the rate at which light and
heat is emitted by the light bulb?
2. The sticker on a compact disc player says that it draws 288
mA of current when powered by a 9 Volt battery. What is the
power (in Watts) of the CD player? Calculate the energy
used if it is put on for 2h?
3. A color TV has a current of 1.99 Amps when connected to a
120-Volt household circuit. What is the resistance (in ohms)
of the TV set and calculate its power?
4. A hairdryer has a power-rating of 750W. If a unit of electricity
costs rs21, how much does it cost to run the appliance for a
year if it is switched on for 10 minutes each day?
5. A cooker has a power-rating of 3kW. If a unit of electricity
costs rs17, how much does it cost to run the appliance for 3
hours?

11. Hazards of electricity
Damaged insulation Overheating of electrical
cables
Hazards in damp conditions direct
contact(carelessness)

12. Hazards of electricity
 Damaged Insulation
The wires in each cable are insulated from one another, and the
whole cable has more protective insulation around the outside. If this
insulation is damaged, there is a chance that the user will touch the
bare wire and get an electric shock. There is also a chance that
current will flow between two bare wires, or from one bare wire and
any piece of metal it comes in to contact with.
 Overheating of cables
Some times another hazard can arise if an excessive current flows
in the wires. They will heat up and the insulation may melt, causing it
to emit poisonous fumes or even catch fire. Thus it is vital avoid
using appliances that draw too much current from the supply.

13. Hazards of electricity
 Damp conditions
When using electricity, it is important to avoid damp or wet
conditions. Because water is an electrical conductor. So if your
hands are wet when you touch an electrical appliance, the water
may provide a conductive path for current to flow from a live wire
through you to earth. That could prove fatal.
 Carelessness
sometimes, people tend to be very careless when handling electrical
cables and appliances. As metal appliances which are not earthed
are great dangers to people. Low electrical sockets can be
hazardous to small children as they may take metal objects and play
with these sockets thus endangering themselves.

14. Safe use of electricity
 Fuses
Fuses are included in circuits to stop excessive currents from flowing. if
the current gets too high, cables can burn out and fire can start. A fuse
contains a thin section of wire, designed to melt and break if the current
gets above a certain valueuses
It is important to choose a fuse of the correct value in order to protect an
appliance.
The current rating of the fuse should be just above the value of the
current that flows when the appliance is operating normally.
Maximum current allowed = 3 A
Fuses rating = 3.1-3.5A
THE FUSE IS A DEVICE
USED TO PROTECT
EQUIPMENT AND
WIRING FROM
EXCESSIVE CURRENT
FLOW.

15. Safe use of electricity
 Circuit breaker
A circuit breaker is an automatic switch which cuts off the current in
a circuit if this rises above a specified value. It has the same effect
as a fuse but, unlike a fuse, can be reset (turned ON again) after it
has tripped (turned OFF).
When the live wire carries the usual operating current, the
electromagnet is not strong enough to separate the contacts.
If something goes wrong with the appliance and a
large current flows, the electromagnet will pull hard enough
to separate the contacts and break the circuit.
The spring then keeps the contacts apart.
After the fault is repaired, the contacts can be
pushed back together by
lifting a switch on the outside of the circuit breaker.

16. Safe use of electricity
 Earthing
Sometimes, even the fuse cannot capture the high
currents coming from the live wire into the household
appliance, earthing further protects the user of the
appliance from electric shock by connecting the metal
casing of the appliance to earth (a wired connection to the
bare ground).
In the event that the metal casing of the appliance
becomes live, earthing diverts large currents into the earth
by providing an alternate path to the large current flow via
the earth wire, rather than through the user’s body.

17. Safe use of electricity
 Double Insulation
Alternatively, instead of earthing, appliance can be made with
double insulation. Double insulation protects the user of the
appliance from an electrical shock by preventing any possibility
of the external casing becoming live, thus eliminating the need
for an earth connection.
First insulation: Insulating electrical cable from the internal
component of the appliance.
Second insulation: Insulating internal metal part which could
become live from the external casing.
Symbol of double insulation

18. Live, Neutral and Earth wires
 Live wire carries electric current to the appliances.
 Neutral wire completes the circuit by forming a path for the
current back to the mains. It is usually at zero volts.
 Earth wire has very low resistance and is usually connected
to the metal casing of the appliances. It forms a safety outlet
for current in case the appliance becomes live.

19. How to wire a mains plug?
 The LIVE wire is BROWN. This is connected to a fuse on the
live pin. The electric current uses the live wire as its route in.
 The NEUTRAL wire is BLUE. This is the route the electric
current takes when it exits an appliance; it is for this reason
the neutral wire has a voltage close to zero.
 The EARTH wire is GREEN & YELLOW and connected to
the earth pin. This is used when the appliance has a metal
casing to take any current away if the live wire comes in
contact with the casing.

20. Why should fuses and circuit breakers
be connected to live wires?
 As mentioned above, live wire is the
one that carries current to the
appliances. If ever there is a too bog
current that is being carried to the
appliance, then it may get damaged.
 In order to avoid this problem, a fuse
or a circuit breaker should be
connected to the live wire, that will
cause the circuit to break if ever the
current is too large.