L4 : Conductors & Insulators - Electricity & Circuit Part, Science, Class 6 Video Lecture

hello friends this video on electricity
and circuits part 4 is brought to you by
exam 4 calm
no more pure from exam 4 different
circuit elements ok the next this is
this circuit which you see here is an
example of a circuit diagram that this
represents a switch this is the symbol
for a switch this is the symbol for a
sale this is these straight lines which
you see these are the symbols for wires
so that is how we draw a circuit diagram
ok so now the question is we understood
that if the circuit is complete
then the bulb will glow so the question
the next question that comes to our mind
is why does the bulb glow I mean who
allows the bulb to glow so is it that if
just if the only requirement that is
here is that the circuit has to become
heat many a times we see that the
circuit is complete but still the bulb
is not glowing because there are other
factors involved as well let us look at
this scenario now here the bulb glows
because current is allowed to flow
through the wire of the circuit so if
you see the electrons are actually
moving over these wires so these wires
are actually allowing the electrons to
move these wires are allowing current to
flow through it and that is why the
current is flowing so even if the
circuit is complete but if these wires
they do not allow current to move
through it in that case also current
will not flow through the circuit and
then the bulb will not glow so here
again let us take the same example of
the bridge which will help you to
understand it better so in this case let
us say that the bridge is intact so
nobody has broken the bridge the bridge
is there the path is there but let us
say the surface of the bridge is very
slippery it is like spilled with oil and
water which makes the surface very
slippery because of which this person is
not able to ride his
by cycle over it and that's how he is
not able to reach be that he is not able
to cross the bridge so in this case the
path is there the path is complete but
the material of the path is such that it
is not allowing the cyclist to move so
that means it is not necessary that all
materials will allow current to flow
through them so there are certain
materials which allow current to pass
through them whereas there are certain
materials which do not allow current to
pass through them so only if the circuit
contains materials which allow current
to pass through them only then the
purple blue because in that case only
the current will actually flow through
the circuit and that's how the berbil
blow so this is another important
requirement now based on where the
materials allow current to pass through
them or not the all materials are
classified into three categories
conductors semi conductors and
insulators
so conductors and insulators are the two
extremes conductors they allow current
to pass through them so they have very
high conductivity conductivity is the
ability to conduct electricity it is the
ability to allow electricity or electric
current to pass through them so they
have very high conductivity
whereas insulators they do not allow so
they have a very low conductivity so
they do not allow current to pass
through them so these insulators are
also known as fewer conductors and many
times the conductors are also called as
good conductors so some examples of good
conductors are metals water these are
good conductors whereas plastic would
glass these are all examples of
insulators so if you take a material
medical plastic and even if you put it
in direct contact with a live wire can
you correct you will not get electric
shock because the plastic will not allow
electricity to pass through it and
therefore
you will not experience any electric
characters but in case you hold a piece
of metal in your hand and then you put
it in contact the life while carrying
current in that case you will get
electric shock because the metal will
allow electric current to pass through
it then water semiconductor
semiconductors the name itself defines
it
it is like intermediate between
conductors and insulators so they have
intermediate conductive it is not that
they are very good conductors at the
same time it is not that they do not
allow for it to pass through them at all
so they have like intermediate
conductivity partially they allow
current to pass through them so some
examples of semi conductors are silicon
germanium gallium arsenide etcetera so
here in this lesson we will be focusing
more on conductors and insulators
so semiconductors are something which
you will learn in your higher classes in
12th so because right now this is the
basics so when you are just learning
what is electric current what happens
when current flows so you will only
focus on the basics so let's see how
adding materials to the circuit can
affect the current flow within the
circuit now let's say we add a new
substance to the circuit which is made
up of a new material so how do no you
may ask that how do I know that if a
substance is a good conductor or a poor
conductor because if the substance is a
poor conductor it will not allow
electric current to pass through the
circuit so let us look at this scenario
so what we do is we take we make a small
circuit where we take a bulb we connect
it to a battery so this cell is nothing
but a battery which has a positive and a
negative terminal so we connect it to
the battery and then we also connected
to the material so let's say the
material in this case is something which
is made up of old metal okay so when we
connected
with the metal what happens and when we
make the circuit complete by switching
it on we see that the bulb glows
now if the bulb glows what does that
mean that means that current flows
through the circuit so if current is
flowing through the circuit what does it
means this particular material which has
been added to the circuit is a good
conductor that is my current is able to
flow through the circuit because had it
been a poor conductor it would is not
allowed current to flow through it in
that case the circuit would have been
broken and therefore the bulb would have
not blown similarly let's say you put a
plastic bottle bit in the circuit now in
this case what happens even when you
switch it on the bulb doesn't glow which
shows that current doesn't flow through
the circuit so current doesn't flow and
why the current doesn't flow because
plastic is a poor conductor of
electricity so it doesn't allow current
to pass through it and therefore the
circuit is not complete so anytime we
for any circuit to be complete now why I
am always taking this example of bulb
because it helps you to understand the
concept easily so whenever you have any
circuit so the first criteria is that
the circuit has to be complete the
second criteria is bad all the materials
involved in the circuit whether it is
the wires or it is any other substance
which is present in the circuit they all
should be good conductors of electricity
only then current will be able to flow
through the circuit so that is the
second requirement so the bulb glows
only when conducting materials are
present in the circuit so this is again
very very important so whichever points
are important I am focusing them because
those are the criteria which need to be
satisfied for a bulb to glow in a
circuit for all in other words for
electric current to flow to flow through
a circuit thank you please visit
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