You must have seen at your home that whenever
you switch on the light on the
television, it gets switched on immediately. 
Why? Because there is a constant flow of 
electricity
into your home as a result of which
whenever you switch on any appliance it gets
switched on immediately. But, how do you
think electricity is reaching your home?
It is being generated at a power station that
is many miles away from your home. So, how do you think it reaches
your home? But before we answer that
question, let us consider a very simple
example.
Over here, a highway has been shown and the car
has to reach from point A to point B.
At point B is located the home of the driver of
the car. So, while coming along the
highway the driver takes the interstate. So
along the interstate, because it is a
highway the driver drives at a very fast
speed because he wants to reach his home
fast.
Now, once he gets off the highway, he comes
on at the interchange. Now, the interchange
is the portion which connects the
highway to the main city. So, once the
driver is on the interchange, his speed 
will reduce comparatively because the
traffic flow is greater. So, he drives
along the interchange and he comes into
the city and he gradually nears his home,
he comes close to his home, that is close to his
neighbourhood. So, once he is in his neighbourhood,
he has to reduce the speed of his car further
because he does not want to put the
residents of the neighbourhood at risk
and once the driver is pulling his car
into the garage, obviously, the speed of
the car will be substantially reduced.
And thus, he will have reached his home.
So, all along the path from A to B, the
driver has changed his speed
substantially, that is decreased his speed in order
to reach from A to B. Now, a similar thing
happens in the case of current.
Now, consider this picture carefully, over here,
we have a power plant that is producing
electricity.
So, this power plant produces electricity
at a very high voltage. Compare the voltage
to the speed of the car in the earlier
case. Over here, a very high voltage is
considered because this voltage has to
travel for long distances, just like in the
previous case where the speed was high
because the driver had to travel a long
distance.
So, now there is voltage, at this voltage,
the current is generated and it travels
along the wires. So before it encounters this
distribution centre it encounters this
transformer which increases the voltage
for transportation because it has
to travel a long
distance. So after this voltage has been
increased to a good amount, it is
distributed to several places in the
city. So, now, before this electricity actually
reaches our homes it encounters a
second transformer, this transformer
decreases the voltage, so that it arrives
at a safe limit at our homes. So this
safe limit of voltage is then coming
to the distribution lines or a 
neighbourhood from which the current or the
electricity is entering our homes.
Notice, that in the previous case
where the driver had reduced his speed in
order to make it safe, so even in this
case, the transformer reduces or
decreases the voltage in order to make
it safe for the current to enter our
homes. Now, consider
a simple case, over here, there is a
fault that has taken place with the
appliance and when the person touches it, he receives
a severe electric shock.
Now, what do you think is happening? Due
to this fault that has taken place, the
entire body of the microwave oven is
getting electrified. So, due to this when the
person is touching it, he receives a
severe electric shock and all the
current from the mains supply is
travelling through his body down to earth. So, such
electric shocks can actually prove to be
very fatal, these can be very fatal
because they can cause severe injuries
and burns or in serious cases it can
also cause harm to the life of the
person. So, in
order to protect oneself from the
various faults that can take place, a
simple technique is applied, earthing of
the appliance is done.
So, when the appliances earth and even when a 
fault takes place the person touching the
microwave oven at the appliance
where the fault has taken place is not
harmed. Because all the charges flow
directly down to earth.
We have studied that the earth is a huge
sink for
charges, electrons and protons alike. So, when
we are incorporating an earthing for the
appliance we find that even though the
appliance is encountering a fault the
appliance itself is not getting
electrified instead the current that would have
otherwise
crowded on the appliance is flowing
directly down to earth and thereby protecting
the appliance as well as the person
touching it.
So, how is this earthing done? Now, consider
a socket that you see normally at your homes,
this is a three pin socket that is
commonly used. Over here, there are three
parts, the first part that is
responsible for the protection of the
person as well as the appliance is known
as the earth socket or the socket
where the earth wire 
is inserted. The other two parts are the
sockets for the live wire and the neutral
wire, the live is a wire through which
electricity reaches our homes and the
neutral is the wire through which
electricity again travels back to the
power station.
Now, you will notice that the earth wire socket
is significantly thicker than the other
two. If you have ever observed a
three pin plug, you will notice that the
earth pin is not only thicker but longer than
the neutral and the live pins. Do you know
why this is so? This is because when you
insert the plug into the socket, the earth
wire being longer is reaching first
inside the socket. So,
even if there is any fault in the line or
the connections, the charges will
directly flow down to earth instead of
damaging the equipment or harming the
person who uses the equipment.
And the earth pin is also thicker than the other two so
that even by mistake it cannot be
inserted into the socket for the live or the
neutral wire. Now, according to the old
convention, the earth wire or the earth socket
is depicted in green, the live wire socket is
depicted in red and the neutral wire socket
is depicted in black.
But there has been a change in
convention of late and the new
convention is slightly different, here
the earth wire still remains green, however,
the live wire is a light brown and the neutral
wire is light blue.
Now, we have studied how electricity is
reaching from the power plant to our home. Now,
what do you think happens to the
electricity once it reaches our homes? Over here,
we have certain parts inside the wiring
of a particular house, so initially when
the power is coming in from
the power station, that is the current is
coming in from the power station, it is
encountering a pole fuse or the company
fuse. This fuse is provided by the
company in order to protect the house
from faults, that is if there is a fault
at the power station side or the company
side, then an excess amount of current
will flow. So, in order to prevent the
house from this excess current, this pole
fuse is used, which breaks if there is a fault.
Moving on, we have what is called a
kWh meter.
This meter is actually used to give us
the reading of the current, in other
words, how much electricity or how much
energy as you can see has been consumed
by the appliances using electricity in
the house.
Moving on further, we have what is called
a Main Fuse and a Local Earthing.
So, let us say that there has been some sort of fault
in this region.
The local earthing ensures that the excess
charges flow down to earth.
And the main fuse is a second step of
security which ensures that if there is
any fault that is occurring in the
region after the pole fuse, if there is
any fault that occurs, then the excessive
current will not reach the appliances in
the home because the main fuse will
break and prevent the current from reaching the
appliances.
And the last equipment before we
actually get the electricity in our
homes is the Mains or the Main Switch.
This main switch is always to be
switched on, so that the current which is
coming from the power station can reach our
home and it can reach all the household
appliances. Whenever the main switch is
switched off, you will notice that
no matter what switch of whichever
appliance you switch on, they will not be
able to function.
Why? Because if the main switch is off, the
circuit that begins absolutely at this
point
will not be able to function because the
switch is open. So, this is how we find
that the power or the current reaches the home
from the power station.
