L1 : Introduction - Capacitor & Capacitance, Physics, Class 12 Video Lecture

hello friends this video on capacitance
and capacitance part 1 is brought to you
by exam feel calm no more fear from exam
the topics to be covered in this lesson
are electrostatics in conductors
dielectrics and polarization capacitance
parallel plate capacitor combination of
capacitors and energy in capacitor so in
this lesson we will basically study
about capacitors
I think this name might be new to most
of you I mean not most of you instead I
would say to all of you so we will first
see what is a capacitor and then we will
go and get into detailed study of
capacitors right so before even we start
knowing what a capacitor is let us see
what is the need of certain capacitor I
mean why are we studying capacitor what
would what is it or where do we see it
around us I hope all of you must be
having several electronic devices at
your house your computer itself you take
as an example now if you see the
interior circuit of your any object of
any of the electronic devices be it your
motherboard or any other electronics be
it a motherboard or any other electronic
device you would see that there is a
board with so many electronic components
embedded on it right which looks
somewhat like this so on this board
itself you see something called
capacitor right so here if you see these
small things which you can see here
right which looks like circles or if you
see it from there or if you try to see
it more closely it will look like
something of cylindrical shape right so
these things are nothing but your
capacitors so basically till now what
idea did you get capacitor must
something which is an which is a kind of
electronic component of which these
electronic devices are made above right
so in this lesson what we will study is
what is a capacitor how does the
capacitor work
what is the function or what is the
purpose of a capacitor why do we use
them in such circuits and all such
things so here you saw where do you
basically see capacitors so that you
just get a rough idea of okay this is
what we are going to learn about right
so now let us come to the slide which
will talk about what is a capacitor
right capacitor is a device that was
clear from the previous picture right so
it is a device that can store large
amount of charge so this capacitor main
purpose of the capacitor is to store
large amount of charge in a small space
so that term capacitor capacitor means
capacitor basically judges the capacity
to store charge so from there you get
the same capacitor right so capacitor
will store huge amount of charge in a
small space so how do we do that how
will this device store charge or what is
the constant moment of what things is
this device made up of so be patient we
will know each of these one by one so
basically what does this capacitor
consists of it is an arrangement of two
conductors separated by an insulator so
again you have two terms here conductor
and insulator so basically I am very
sure that all of you must be knowing
what is a conductor and what is an
insulator conductor is something which
allows electricity to pass through it so
which we mostly know all as good
conductors of electricity right and when
we say an insulation it means something
which is not a good conductor or which
is a bad conductor
which doesn't allow electricity to pass
through it so basically a capacitor will
consist of two conductors and the two
conductors will be separated from each
other by an insulator now see here when
we talk about I mean all of you will be
knowing these definitions of conductors
and insulators but when we try to know
how does this arrangement helps in
storing charge we will have to know more
about conductors as well as insulators
so first here let us look at the
arrangement how does it roughly look
like so let us suppose these two are two
plates or which are conductors that is
they allow electricity to pass through
it now they are separated so these two
plates are conductors they are separated
from each other by this distance so what
is there in this distance this region is
filled with nothing but insulators so
this region has insulated in it so this
medium is an insulator which is a bad
conductor of electricity so now it is
not necessary that it has to be in this
form capacitor can be any such
arrangement for example not only these
parallel plates instead of the plates
you can also have two spherical
conductors which are separated by an
insulating medium so that is also
possible that is also known as a
capacitor so now our aim is to see how
this arrangement help in storing charge
so we will study about that before that
let me tell you how do we represent a
capacitor in our circuit diagrams like
you all know right and when we talk of
visits we we draw the circuits that is
what we call a circuit diagram just now
I showed you the circuit of a
motherboard right so when in in terms of
visits when we theoretically want to
draw a circuit diagram there are certain
symbols which we use for each device so
the symbols which we circuit symbol
which we use for a capacitor is this one
so these two lines represent two
conducting plates and separated by some
distance this is how it is represented
in our circuit diagrams right so
remember this representation because
once you pass through the first say
seven to eight slides and then you will
see these these symbols everywhere so
now how how does this gap capacitors
look like if you go to your Physics
Laboratory in your schools you would see
if you ask the lab guy that gives me a
capacitor they look so good like this
they are all different kinds of
capacitors with different capacity
ranges right so they are all this is how
your real capacitors look like they will
be very tiny they are not some huge
things as as you have already seen right
your motherboard or any electronic
device which you see inside that device
you have so many small small circuit
elements and one of those small circuit
elements is a capacitor so these are
also very small small objects right so
this is how a capacitor look like so as
I told capacitors can also be of this
form here you can see there these are
the two spheres the two spheres are
conducting spheres so they are two
conductors separated by insulated medium
that means the space between the two
spheres will be separated by some
insulating medium right so this was the
very basic basic of what a capacitor is
so till now what did we learn we learn
that a capacitor is a device that can
store huge amount of charge in a small
space right what what does it made up of
it is made up of two conductors
separated by an insulator now in order
to know how this arrangement stores
charge it is important to know how does
a conductor behave in electric field for
example because this is all we are
studying about now right we will talk
about charges as soon as charges come
into picture too many charges coming
into picture electric fields will come
into picture electrostatic potential
will come into picture right all these
things will start playing a role so now
we have to see how does all this
phenomenon of electrostatics affect a
conductor or effect and insulator
because we I don't think you are aware
of the
you want to slow up and apt Elizabeth
fantastic insulin is a bad conductor so
before I talk about how a capacitor
works I will talk about the behavior of
conductors in electrostatics or
basically we can say that we will study
about electrostatics of conductors right
so for the next few slides we will study
about conductors how they behave in
electric field right and then we will
talk again about capacitors and then
keep continuing so let us first have a
quick review of conductors vs.
insulators I know that all of you are
aware but still let me have a quick
review so let me first talk about
conductors as you all know conduct
electricity examples most famous
examples metals metals are good
conductors of electricity this is what
you have been studying since your lady
fifth grade or sixth grade right so
conductors examples metal salt solutions
acids of human body these are all the
most famous examples of conductors right
conductors have free electrons or ions
free electrons or ions are charged
carriers this is an important point
because this is the basic fund out which
makes a conductor conduct electricity
right because in conductors we have free
electrons what a free electrons okay let
me explain this even though you know it
let me explain it for review so what
happens basically is that when we
basically look at the configuration of
any metal or any ions what water ions
basically ions are nothing but which has
some positive charge some positive
charge or negative charge some childhood
so how are is formed ions are formed
when a metal loses one electron or gains
one electron right so that means in case
of ions or in case of metals their
electronic configuration is such that
the electron in the
outermost said outermost shell is free
so that electron is not very tightly
bound to the atom or to the nucleus
rather so that is why when it gets some
opportunity to jump somewhere or the
other it jumps so that electron or these
kind of ions they are free to move
around so these three electrons
basically conduct the electricity so
they act as the charge carriers right so
this is what happens in case of a
conductor whereas when we talk of
insulators they do not conduct
electricity for example rubber plastic
glass so they do not have any charge
carriers to conduct electricity so if we
look at some example let us suppose this
is a metal so as I told you these metals
will have free electrons which are free
to move around here and there so these
free electrons I mean don't just go
behind this picture you will not see a
metal in your hand and inside that
electrons are running and jumping here
and there what I am trying to say is
what does this metal made up of any
object which we you see you around
yourself what does it made up of this
metal is also made up of atoms right it
has atoms those atoms in turn will have
a nucleus inside which you have proton
for example this metal will made up of
is made up of some atoms let us suppose
these are my atoms now the these are my
molecules I'm sorry these molecules are
again made up of atoms right let us
suppose these are the atoms now each of
these atom will have a nucleus inside
which you will have your proton and
neutron and the electrons revolving
around them right each of these atoms
will have that now you go into so that
is when we look at the atomic structure
it looks somewhat like this if you look
at this this is your nucleus inside
which you have your neutrons and protons
right and these are the electrons which
are revolving outside so what happens in
case of metals or rather in case of
conductors
one of these electrons are not very
tightly bound to this nucleus so now if
it is not very tightly bound there is a
possibility that if it gets a chance it
will try to move around here in their
right
so these free electrons basically act as
charge carriers since they are free to
move around here and there so they are
able to carry charge from one place to
another and as a result conductors are
able to conduct electricity contrary to
that when we talk about insulators let
us suppose that let me talk about a log
of wood so in that case what happens
they do not have free electrons inside
them because of which there is no
conduction of electricity so this is
something which you already knew right
you already knew what is a conductor
what is a insulator why conductors
conduct electricity and why insulators
do not so now that with this basic idea
we will now study the electrostatics of
conductors that is how to conduct us
behave in presence of electric field
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