CBSE Class 11 > Class 11 Videos > Venturimeter - Mechanical Properties of Fluids
Venturimeter - Mechanical Properties of Fluids Video Lecture - Class 11
Text Transcript from Video
hello friends this video on mechanical
properties of fluids
r20 is brought to you by example.com no
feel from exam and now we studied about
the flow speed of incompressible fluids
that is how do we determine the speed of
and how is the speed of incompressible
fluid Q a tube of value length is
determined now we will learn about a
device which is used to measure the
speed of the incompressible fluid this
is known as venturi meter venturi meter
is a device to measure the flow speed of
incompressible fluid so how does it look
like it basically consists of a tube of
a broad diameter if you see this is a
tune of rod a needle with a larger
cross-sectional area however it has a
small construction at the middle that
means this tube is of broad diameter
with the constriction in the middle if
you see this pink color too you can see
how it look like now it is attached to a
u-tube manual we studied about u-tube
manometer and what was it it was a
device which is used to measure the
gauge pressure that is the gauge
pressure means the difference of
pressure between the atmosphere and the
system so basically the venturi meter
consists of a broad tube with
constriction at the middle this is the
constriction it consists of a u-tube
manometer one end of the monitor is
connected to the constriction and the
other end is connected to the broader
side of the venturi meter that is one
arm of the venturi meter one arm is at
the constriction and the other one is
the broader net point at this point yeah
so this is how it looks like they not
your man winter is filling with any
liquid of density same row let us
suppose this consists of this is filling
with a liquid of density Rho so what
happens basically is let us suppose that
this area at the broader net point the a
cross sectional area is even and let us
suppose that air or any fluid which
moves to this art as a velocity V right
similarly let us consider that the cross
sectional area at this constriction is a
2 and a velocity with which a fluid
moves at this part is beat so according
to the equation of continuity again
wherever the area and smooth the
velocity would be less so if you see
that since E 1 is greater than a 2 that
is in this broader neck point the area
is more therefore the velocity would be
lesser when compared to the velocity at
this constriction right similarly we
also know that pressure is inversely
proportional to area so at this
broadening point the aliens more
therefore the pressure is less let us
suppose the pressure here is P 1 and the
pressure at the constriction is P 2 so
what happens you find from here that
pressure P 1 is lesser than the pressure
P 2 right because area a 1 is greater
than area e 2 so since al is more the
pressure is lesser now because due to
this difference in pressure as we
already know that a fluid moves when
there is a pressure difference because
of this difference in pressure at this
end and the constriction the fluid which
is there in the YouTube it moves and
this movement of the fluid is marked by
the
level of the fluid in this one so this
is how it can be destroyed if you
observe this diagram initially this was
the level of the liquid or the fluid
right so now because of the pressure
difference when air is blown into the
venturi meter through this end the
velocity of the air being the
cross-sectional area at this end being
both the velocity is lesser as it
reaches the constriction part the
velocity increases similarly since the
cross-sectional area here is gold
the pressure is listened as it reaches
the constriction the pressure again
increases due to this pressure
difference what happens is the liquid
which is air in this YouTube it starts
flowing due to the flow of the liquid
the level of the liquid in this column
of the g-tube changes to as a result we
can actually the value of velocity due
to the changed qalam rise of the fluid
in the you tube so that is what we will
derive in our next slide that how do we
exactly calculate the velocity of the
fluid but here I told you what is the
concept behind which there is a change
in the volume of the u-tube value net
now let us determine mathematically the
speed with which the fill how do we guys
can evaluate the speed of the fluid as
it will do we assume that the area
around of the broader length is given
and the velocity v1 so according to the
equation of continuity we can see that a
1 v1 is equal to a2 v2 so where a point
waiting is the area and velocity at the
constriction and even and we will add
area and vanilla and velocity at a
broadening of the venturi meter so from
this we can say that v2 is equal to a 1
by 18 into v1
this video is nothing like this Hewitt
speed which we want to determine now let
us apply Bernoulli's equation according
to Bernoulli's equation the pressure the
sum of pressure kinetic energy per unit
volume and for Angel energy per unit
volume at the constriction should be
equal to the sum of these two quantities
at the broader make point of the venturi
meter so p1 plus half Rho V 1 square
plus Rho G H is equal to p2 plus half
Rho V 2 square plus Rho G H so if you
see that this H is equal in both the
cases right because in this case that
venturi meter tube is not at varying
heights
therefore the height of the venturi
meter cube is the same so we can cancel
these two terms as the pipe is
horizontal therefore from this we can
write p1 minus p2 is equal to half Rho
v2 square
- v1 square now from the first equation
which we wrote from equation of
continuity we found that field U is
equal to a 1 by a 2 into V 1 so from
this equation we can write V 1 in terms
of people so V 1 can be written as a 2
by a 1 into V so let us write that this
means we have into Rho V 2 square - so
this will be half Rho B 2 square minus V
1 square so from this first equation of
continuity we can write V 2 as a 1 by a
2 into V 1 that is half into Rho a 1
square by a 2 square into V 1 square
minus V 1 square so this we can write as
half Rho V 1 square a 1 square by a 2
square minus 1 now as I told you because
of this difference in pressure the fluid
in a YouTube changes its level because
of the pressure difference the fluid
starts flowing and as a result the level
in the YouTube changes so we can say
that this pressure difference causes a
change in the level of the fluid in the
column so we can say this is equal to H
Rho G so p1 minus p2 is half Rho V 1
square a1 square by a 2 square minus 1
this is equal to H Rho G so Rho will get
cancelled on both sides so we get V 1
square is equal to 2 inch Rho G so here
in this case we see that the value of
Rho is different in both the case
the first case this row is basically the
density of the fluid this is H Rho G
then we say this is H Rho G what is this
role is basically the density of the
fluid inside the you do man you loot it
let us denote it as Rho M so this is Rho
M so they will not get cancelled so the
velocity v1 Square will be equal to 2 H
Rho M into G divided by Rho into a 1
square by a 2 square minus 1 to the
power minus 1 by 2 so this is the
velocity so this is the flow speed of
Earth of an incompressible fluid so this
is how we determine the velocity using a
venturi meter so let us have a quick
review what we did in this case we told
that the venturi meter has a small
constriction whose cross-sectional area
is given you and the velocity of the
fluid at the constriction is V 2 and on
the broader side the cross sectional
area is e 1 and the velocity of the
fluid is V 1 according to equation of
continuity a 1 V 1 is equal to alpha we
do so we can say V 2 is equal to a 1 by
a 2 into V 1 now we apply Bernoulli's
equation at the constriction as well as
at the broadening of the venturi feature
so this is the Bernoulli's equation Rho
G H gets cancelled because it is a
horizontal tube so therefore the height
at the constriction as well as the
height at the broader nape is the same
so these two terms will get cancelled
from here we get P 1 minus P 2 is equal
to this expression now because of the
difference in the pressure the fluid if
the u-tube manometer changes its level
so that means due to this pressure
difference P 1 minus P 2 they
a change in the level of the phylum that
is H Rho G so you can say that P 1 minus
P 2 is equal to H into Rho and mu G what
is this Rho F this is basically the
density of the fluid inside the U tube
whereas what is this Rho this is the
density of the fluid which passes
through them venturimeter tube so both
the rows are different now we equate
both the equation and we find out the
value of V 1 as this expression so this
is how we evaluate or determine the
value of the fluid speeds using a
venturi image let us look at a practical
application venturi meter this now I
told you about the venturi meter and how
it works
now talk about certain things which we
use in our day-to-day life and they also
use the same principle so here we'll
take the example of a spray gun so all
of you must have seen spray gun or a few
water which is normally used in our
day-to-day life so how do they function
it is very good similar what we
discussed in the venturi meter what
happens here is let us suppose this is
the bottle which is filled with the
fluid here is a pipe which goes straight
till this constriction where is the
million - the venturi meter there is a
narrow end of the pipe which you can
consider this end with a greater
cross-sectional area and then suddenly
there is a constriction Adam middle so
you can consider this as the
constriction so here the area decreases
so this has larger area so the pressure
here is less whereas here the area is
less so the pressure is more now because
of this pressure difference then what
happens generally when we pump it will
replace the handle some pressure is
applied from this end as a result the
air flows in now the velocity of the air
again changes depending upon the cross
sectional area also because of the
difference in the process
area there is a difference in pressure
due to this pressure difference the
level of the liquid in this pipe Rises
so what happens it draws the liquid from
this trough which contains this liquid
as a result the liquid moves up and to
this opening it comes out and we get it
in the form for spring
since this end is open so what happens
when the hip width comes up to this pipe
it directly goes out and it is played so
basically what happened was because of
the difference in the cross-sectional
area there was a pressure difference
which forced the fluid to flow the fluid
move up to the pipe and to this opening
it came out and it was faked
thank you please visit exam feel calm to
watch free educational videos try free
online tests get the best quality study
materials study from the best tutors and
mentors and much more thank you once
again
properties of fluids
r20 is brought to you by example.com no
feel from exam and now we studied about
the flow speed of incompressible fluids
that is how do we determine the speed of
and how is the speed of incompressible
fluid Q a tube of value length is
determined now we will learn about a
device which is used to measure the
speed of the incompressible fluid this
is known as venturi meter venturi meter
is a device to measure the flow speed of
incompressible fluid so how does it look
like it basically consists of a tube of
a broad diameter if you see this is a
tune of rod a needle with a larger
cross-sectional area however it has a
small construction at the middle that
means this tube is of broad diameter
with the constriction in the middle if
you see this pink color too you can see
how it look like now it is attached to a
u-tube manual we studied about u-tube
manometer and what was it it was a
device which is used to measure the
gauge pressure that is the gauge
pressure means the difference of
pressure between the atmosphere and the
system so basically the venturi meter
consists of a broad tube with
constriction at the middle this is the
constriction it consists of a u-tube
manometer one end of the monitor is
connected to the constriction and the
other end is connected to the broader
side of the venturi meter that is one
arm of the venturi meter one arm is at
the constriction and the other one is
the broader net point at this point yeah
so this is how it looks like they not
your man winter is filling with any
liquid of density same row let us
suppose this consists of this is filling
with a liquid of density Rho so what
happens basically is let us suppose that
this area at the broader net point the a
cross sectional area is even and let us
suppose that air or any fluid which
moves to this art as a velocity V right
similarly let us consider that the cross
sectional area at this constriction is a
2 and a velocity with which a fluid
moves at this part is beat so according
to the equation of continuity again
wherever the area and smooth the
velocity would be less so if you see
that since E 1 is greater than a 2 that
is in this broader neck point the area
is more therefore the velocity would be
lesser when compared to the velocity at
this constriction right similarly we
also know that pressure is inversely
proportional to area so at this
broadening point the aliens more
therefore the pressure is less let us
suppose the pressure here is P 1 and the
pressure at the constriction is P 2 so
what happens you find from here that
pressure P 1 is lesser than the pressure
P 2 right because area a 1 is greater
than area e 2 so since al is more the
pressure is lesser now because due to
this difference in pressure as we
already know that a fluid moves when
there is a pressure difference because
of this difference in pressure at this
end and the constriction the fluid which
is there in the YouTube it moves and
this movement of the fluid is marked by
the
level of the fluid in this one so this
is how it can be destroyed if you
observe this diagram initially this was
the level of the liquid or the fluid
right so now because of the pressure
difference when air is blown into the
venturi meter through this end the
velocity of the air being the
cross-sectional area at this end being
both the velocity is lesser as it
reaches the constriction part the
velocity increases similarly since the
cross-sectional area here is gold
the pressure is listened as it reaches
the constriction the pressure again
increases due to this pressure
difference what happens is the liquid
which is air in this YouTube it starts
flowing due to the flow of the liquid
the level of the liquid in this column
of the g-tube changes to as a result we
can actually the value of velocity due
to the changed qalam rise of the fluid
in the you tube so that is what we will
derive in our next slide that how do we
exactly calculate the velocity of the
fluid but here I told you what is the
concept behind which there is a change
in the volume of the u-tube value net
now let us determine mathematically the
speed with which the fill how do we guys
can evaluate the speed of the fluid as
it will do we assume that the area
around of the broader length is given
and the velocity v1 so according to the
equation of continuity we can see that a
1 v1 is equal to a2 v2 so where a point
waiting is the area and velocity at the
constriction and even and we will add
area and vanilla and velocity at a
broadening of the venturi meter so from
this we can say that v2 is equal to a 1
by 18 into v1
this video is nothing like this Hewitt
speed which we want to determine now let
us apply Bernoulli's equation according
to Bernoulli's equation the pressure the
sum of pressure kinetic energy per unit
volume and for Angel energy per unit
volume at the constriction should be
equal to the sum of these two quantities
at the broader make point of the venturi
meter so p1 plus half Rho V 1 square
plus Rho G H is equal to p2 plus half
Rho V 2 square plus Rho G H so if you
see that this H is equal in both the
cases right because in this case that
venturi meter tube is not at varying
heights
therefore the height of the venturi
meter cube is the same so we can cancel
these two terms as the pipe is
horizontal therefore from this we can
write p1 minus p2 is equal to half Rho
v2 square
- v1 square now from the first equation
which we wrote from equation of
continuity we found that field U is
equal to a 1 by a 2 into V 1 so from
this equation we can write V 1 in terms
of people so V 1 can be written as a 2
by a 1 into V so let us write that this
means we have into Rho V 2 square - so
this will be half Rho B 2 square minus V
1 square so from this first equation of
continuity we can write V 2 as a 1 by a
2 into V 1 that is half into Rho a 1
square by a 2 square into V 1 square
minus V 1 square so this we can write as
half Rho V 1 square a 1 square by a 2
square minus 1 now as I told you because
of this difference in pressure the fluid
in a YouTube changes its level because
of the pressure difference the fluid
starts flowing and as a result the level
in the YouTube changes so we can say
that this pressure difference causes a
change in the level of the fluid in the
column so we can say this is equal to H
Rho G so p1 minus p2 is half Rho V 1
square a1 square by a 2 square minus 1
this is equal to H Rho G so Rho will get
cancelled on both sides so we get V 1
square is equal to 2 inch Rho G so here
in this case we see that the value of
Rho is different in both the case
the first case this row is basically the
density of the fluid this is H Rho G
then we say this is H Rho G what is this
role is basically the density of the
fluid inside the you do man you loot it
let us denote it as Rho M so this is Rho
M so they will not get cancelled so the
velocity v1 Square will be equal to 2 H
Rho M into G divided by Rho into a 1
square by a 2 square minus 1 to the
power minus 1 by 2 so this is the
velocity so this is the flow speed of
Earth of an incompressible fluid so this
is how we determine the velocity using a
venturi meter so let us have a quick
review what we did in this case we told
that the venturi meter has a small
constriction whose cross-sectional area
is given you and the velocity of the
fluid at the constriction is V 2 and on
the broader side the cross sectional
area is e 1 and the velocity of the
fluid is V 1 according to equation of
continuity a 1 V 1 is equal to alpha we
do so we can say V 2 is equal to a 1 by
a 2 into V 1 now we apply Bernoulli's
equation at the constriction as well as
at the broadening of the venturi feature
so this is the Bernoulli's equation Rho
G H gets cancelled because it is a
horizontal tube so therefore the height
at the constriction as well as the
height at the broader nape is the same
so these two terms will get cancelled
from here we get P 1 minus P 2 is equal
to this expression now because of the
difference in the pressure the fluid if
the u-tube manometer changes its level
so that means due to this pressure
difference P 1 minus P 2 they
a change in the level of the phylum that
is H Rho G so you can say that P 1 minus
P 2 is equal to H into Rho and mu G what
is this Rho F this is basically the
density of the fluid inside the U tube
whereas what is this Rho this is the
density of the fluid which passes
through them venturimeter tube so both
the rows are different now we equate
both the equation and we find out the
value of V 1 as this expression so this
is how we evaluate or determine the
value of the fluid speeds using a
venturi image let us look at a practical
application venturi meter this now I
told you about the venturi meter and how
it works
now talk about certain things which we
use in our day-to-day life and they also
use the same principle so here we'll
take the example of a spray gun so all
of you must have seen spray gun or a few
water which is normally used in our
day-to-day life so how do they function
it is very good similar what we
discussed in the venturi meter what
happens here is let us suppose this is
the bottle which is filled with the
fluid here is a pipe which goes straight
till this constriction where is the
million - the venturi meter there is a
narrow end of the pipe which you can
consider this end with a greater
cross-sectional area and then suddenly
there is a constriction Adam middle so
you can consider this as the
constriction so here the area decreases
so this has larger area so the pressure
here is less whereas here the area is
less so the pressure is more now because
of this pressure difference then what
happens generally when we pump it will
replace the handle some pressure is
applied from this end as a result the
air flows in now the velocity of the air
again changes depending upon the cross
sectional area also because of the
difference in the process
area there is a difference in pressure
due to this pressure difference the
level of the liquid in this pipe Rises
so what happens it draws the liquid from
this trough which contains this liquid
as a result the liquid moves up and to
this opening it comes out and we get it
in the form for spring
since this end is open so what happens
when the hip width comes up to this pipe
it directly goes out and it is played so
basically what happened was because of
the difference in the cross-sectional
area there was a pressure difference
which forced the fluid to flow the fluid
move up to the pipe and to this opening
it came out and it was faked
thank you please visit exam feel calm to
watch free educational videos try free
online tests get the best quality study
materials study from the best tutors and
mentors and much more thank you once
again
About this Video
Apr 22, 2026 Last updated
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