L16 : Equivalent Capacitance - Capacitor & Capacitance, Physics, Class 12 Video Lecture - Class 12 | Best Video for Class 12

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tell part 15 before going ahead with
part 16 so you will have to calculate
the equivalent capacitance of this
circuit between these two points and so
if you see there are five capacitors
attached here again
so how can you rearrange this capacitor
if you look at it please do not go by
loops all the time I have seen many
students what they do is whenever they
see that there are three capacitors at
it side by side that means they are in
series and if they are arranged one
above the another that means they are in
parallel that is a very wrong way of
solving for equivalent capacitance
always think logically for example here
you have the two ends at a and B so if
you start from a come at this point what
do you see between this this is the
starting point from there the three
capacitors are joined and all the three
capacitors ends at the same point so
that means all these key capacitors for
all these three capacitors both their
ends meet at the same point that means
these three capacitors are in parallel
if both ends of the capacitor meet at
the same point that means they are
across the same potential difference so
C 1 C 2 C 3 these three are in parallel
combination now similarly if you look at
C 4 and C 5 there for them also they are
starting at the ending points are the
same and they are both joined in the
scheme points on both sides that means C
4 and C 5 also means a parallel
combination so it has calculated this
equivalent capacitance
let us call this as C - equivalent
capacitance of means 3 similarly let us
call the equivalent capacitance of these
two as C Double Dash
so what will be C - C capacitors in
parallel
so for parallel we do C 1 plus C 2 plus
C 3 right so it will be 2 plus 2 plus 2
that is 6 micro patterns what will be C
double dash that will be 2 plus 4 that
is 6 my parents so now what will be your
setting how will your self it look like
now I can draw the circuit like this
this is my D from a we reach this point
and instead of drawing these three
capacitors we can just draw C - because
C - is the equivalent capacitance of
these 3 then again I go down I reach
this point that is this point instead of
drawing these 2 capacitors
I'll just wrong C Double Dash and I
finally in that point B so how does
yourself it look like now ii starts from
a point ii it moves to one capacitor
then goes to another capacitor and then
goes to b so this is a series
formulation right the series combination
starts from a point goes to a capacitor
goes to another capacitor and reaches at
another point
they I put the charge on both the
capacitor is C because charge is not
getting distributed same charges going
to both of them so now we see that C -
and C double - they make a series
combination right so what will be the
equivalent capacitance of the circuit
that will be 1 by C reading is equal to
1 by sin - plus 1 by C double - that is
1 by 6 plus 1 and 6 which is equal to 1
by T therefore equivalent capacitance of
the circuit is equal to 3 - pallets
right so this is how we solve problems
to calculate the equivalent capacitance
of a circuit now we will solve many more
now so let us look at the second circuit
because that it looks somewhat like this
so what do you think about C 1 C 2 C 3
are they in series or parallel it is
just that the wires are bent but
otherwise it is almost similar to C 1 C
2 C 3 is equivalent in this setting C if
you look at it it stacks at this point a
straight wire joining C 1 teams to it
via join you see two again a straight
while you're turning C 3 so it is
basically you can view with like this
one so that means C 1 C 2 and C 3 these
three make a series combination what
about this point if you look at this
point BH 2 points and the starting and
ending points of C 4 and C 5 that means
C 4 and C 5 makes a parallel combination
so let us say equivalent capacitance for
this is C - equivalent capacitance for
this is C double - because let us
calculate C - for series combination 1
by C dash is equal to 1 by C 1 plus 1 by
C 2 plus 1 by C 3 so let us put the
values 1 by 6 plus 1 1 6 plus 1 1 6 so
that is equal to 1 by 2 therefore C Dash
is equal to 2 micro farad's now let us
calculate C Double Dash so C Double Dash
is parallel formulation of C 4 and C 5
so this will be equal to C 4 plus C 5
that is equal to 6 the 6 that is equal
to 12 so C Double Dash comes out to be
12 micro farad's right so now how will
your circuit look like this is your
starting point and then you have C dash
then you reach the other point and then
you have C double cash this is your
ending point so this is almost similar
to the same thing you start at one point
one capacitor the next capacitor then
your terminating point therefore C
equivalent will be basically C and C -
making a series population
therefore C equivalent online price
equivalent is equal to 1 by C dash plus
1 by C double dash that is equal to 1 by
2 plus 1 by 12 is 12 6 plus 5 that is
equal to 7 by 12 therefore C equivalent
that is equivalent capacitance opposite
it is equal to 12 by 7 microcoulombs I
am sorry my preference right okay
let us look at yet another circuit so
let us examine this circuit and also you
have to calculate the equivalent
capacitance between a and B so if you
look at a these two points we join C 1
and C 2 which says that C 1 and C 2
makes a parallel combination similarly
if you look at C 3 and C they are also
joined between 2 points so C 3 and C
food again make a parallel combination
right so let us call this as C dash this
equivalent capacitance as C Double Dash
so what will be C dash it will be C 1
plus C T which is equal to 3 plus 3 that
is 6 micro farad let's calculate C
Double Dash that is C 3 plus C 4 which
is equal to 3 plus 3 is equal to 6 micro
farad's now if we redraw the circuit
what happens this is my point II instead
of C 1 C 2 I draw C dash similarly
instead of C 3 C 4 I draw C Double Dash
and then I have this capacitor C 5 and
this is point B so we see C - C Double
Dash and C 5 so what do we see we see
that C - C Double Dash and C 5 these
three form a series combination right
therefore the net equivalent capacitance
of the side equity when divided by C
dash plus 1 by C Double Dash plus 1 by C
5 so this is equal to 1 by 6 plus 1 by 6
plus 1 by 3 so this is equal to C 1 plus
1
so this is 4x6 therefore the equivalent
capacitance becomes equal to 6 5 4 that
is equal to 1 point 5 micro farad so
this is the equivalent capacitance of
the circuit again another problem now I
think since you have solved 2 3 if it
must be looking like quite simple for
you because now you are getting used to
how to solve equivalent capacitance for
circuits so here if you look at it first
you look at C 2 and C 3 they are in
parallel right so C 2 C 3 weeks are
parallel combination and I would tell
you friends that solve as many problems
as you can on capacitance on circuits so
that your concepts become very clear
because only understanding the concepts
will not help you much in scoring very
well in your exams because it exempts
mainly emphasize on numerical problems
and not only talking about the board
exams but I'm also talking about several
entrance examinations for big students
generally appear after their class 12 so
it is very much required at first you
clarify your basics then you solve many
problems as many problems as you can and
keep solving them first you solve some
basic problems simpler problems then
gradually start solving some difficult
problems so that will help you to build
your concepts stronger so here C 2 and C
3 are in parallel combination so let us
call their equivalent capacitances c
dash so c dash will be equal to C 2 plus
C 3 that is 3 plus 3 which is equal to 6
micro parents now we can redraw the
circuit let us call this point as B this
point is B so from a we have C 1 after C
1 instead of these two I draw C dash and
then again I have C 4
so basically how does the circuit look
like C 1 C - and seafood are all in
series C well C - and support the for a
series combination their food the
equivalent capacitance of the circuit is
equal to 1 by C 1 plus 1 by C dash plus
1 by C 4 so this is equal to 1 by 6 plus
1 by 6 plus 1 by 6 so this is equal to 3
by 6 or we can say equivalent
capacitance of the circuit is equal to 2
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