L3 : Electric Circuit - Chemical Effects of Current, Science, Class 8 Video Lecture

hello friends this video on chemical
effects of current part 3 is brought to
you by exam calm no more fear from exam
so now the question is when exactly does
the bulk flow now we have already seen
that initially when you do not switch it
on the bulk doesn't blow and it flows
only when this you switch it on or when
you complete the circuit so this is
known as a complete circuit where it
provides that there is no break in
between
let us call a complete circuit but the
question is what special happens when
this circuit gets completed and while
the world facade glowing when the
circuit was incomplete because this
circuit is nothing but like a path for
the current to flow so current needs a
part it means a role let us take one
simple example in order to understand
what is set it let us suppose you have a
bridge right so you can see the bridge
and this bridge connects two places so
let us see it connects two pounds a and
B so on this side of the bridge you have
a and on the other side you have B so if
you want to reach from A to B you need
to cross this this bridge so basically
you did you can imagine it like this
that there is a big river between a and
B so the only way you can go from A to B
or from B to a is through this bridge
see handy can see this person on a cycle
he is trying to go from A to B and he is
traveling on the bridge
so this bridge is actually providing the
person a path to reach from to travel
from A to B now just imagine a situation
where the bridge is broken so here you
can see the bridge is broken now once
the bridge is broken here what do you
think will happen to the cyclist now he
will reach up to this point but from
here there is no path now since there is
no path do you think that he will be
able to reach down me no so the current
so this person is like current or the
charges
the charges will be able to flow only if
there is a path so if the path is broken
in between them current will not be able
to flow right so the similar thing
happens in case of this circuit also so
when that Daniel circuit is complete
only then current will flow through the
circuit and when current flows through
the circuit only then what will happen
the current will be able to heat the
filament of the coil and that is when it
will blow so every current needs a path
to travel and that path is provided by
the electric circuit therefore apparent
flows only when the circuit is completed
so all the now you can understand how
your the bulb tube lights and fans they
start when you switch it on because the
switches are arranged in their circuit
in such a way that as soon as soon as
you press the switch the circuit gets
completed and that is how the appliances
flows when you switch you top the
circuit again breaks and that is why the
bulb gets switched off so that is how it
works so now let us talk about electric
circuit because I am using the term
circuit quite often so electric circuit
is a path for current to flow as I was
telling you that it is the path required
for current to flow only when there is a
complete path current will be able to
flow so normally how do we represent an
electric circuit in a diagram so we make
use of circuit diagrams where we use
specific symbols to represent specific
things so this circuit diagram is drawn
using the conventional symbols of
different circuit elements now water
circuit elements the circuit elements
could be the various things that are
present in a circuit for example battery
for example the resistors the capacitors
so all these things are like the circuit
elements now what each circuit element
there is a specific symbol which is used
wrong it is not always possible to draw
a circuit
draw a battery you draw a resistance you
draw then dissect it like that it is
going to consume a lot of time so
therefore there are some very simple
symbols which are used for each of these
things and which we make up these simple
symbols to design the circuit or to draw
a circuit diagram so let us look at some
of the common symbols which are being
used now how do we represent wires so
why am i represented by straight lines
like this you want to represent a cell
how do you represent it you represent it
like this now any cell will have a
positive terminal and the negative
terminal because cells are the sources
of electric current for electric current
to flow you need a positive terminal you
need a negative terminal so this cell
you have the longer strand represents
positive terminals the smaller one
represents negative terminal how do you
represent a battery
what does battery how a battery and the
cell are different from each other so a
bad thing basically is like a bigger
version of cell you can say so inside a
bad battery you have multiple cells so
how do you represent a battery it will
be represent like this combination of
multiple cells so that is a battery so
that means both cells or batteries they
are like source of electric current so
batteries and they have a lot of cells
so they can provide more cutting down
how do you represent a key he is nothing
but key or switch whatever you call it
how do you represent them in a
surveillance now there are two ways of
representing McKee now a key can be open
a key can be closed what do we mean by
open open means it is the key switches
off the second option that is possible
is the key is closed key is closed means
the switch is on so he are switch so
these are the two scenarios which we
have to be present now a key which is on
is often represented
like this that means the key is open so
the switch is off you see there is a
breakage in the circuit now if it is
closed
in that case it will be a straight line
that means it has got closed so the
circuit it's completed so that is one
way there is another way of representing
the same thing if the key is open you
represent it as like this and if it is
closed
it is represented as like this so both
of them these can be used both of these
symbols can be used now so these are
some of the common things which we will
be using as of Nana as we go to your
higher classes you will get to know
about other circuit elements also like
resistance capacitance volt meter and so
right now we will just consider these
symbols these simple symbols random so
now let us try to draw a circuit using
these symbols now let us try to draw the
same circuit where you have a bun you
have a battery connected to the bulb and
you have a key so how will you connect
it so you will connect it with the wires
so let us suppose we use our wires so
the wires will connect from a battery so
faculty or a cell which has a positive
and a negative terminal now you will
also have a key like this and let us say
you have a bun here and this is how it
is connected so this is your cell this
is the key so right now the key is open
source which is off so the valve is not
glowing now as soon as you switch it on
it will become like this right and the
bulb will start to glow so this is how
we draw circuit diagrams thank you
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