Viscosity (in detail) Video Lecture - NEET

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that you have watched part 1 to part 19
let's start talk about viscosity so
let's talk about viscosity so if you see
if you see the honey you see the veins
if sis is very thick gatling and it
drips very slowly
same thing with chocolate if you have
chocolate or melt chocolate did you see
the way if you take out in a spoon if
you see the way it drips is very slowly
and very gently but let's suppose here
if you see are let's suppose we have
milk in this and we have water and this
rate both within different whiskers of
stands and we put some ice cube on both
now if you see this flickers a lot but
this one if you see it didn't go out but
did you see in this glass the milk also
came out it's if you have a glass of
water and we will just drop eyes it will
come out but if you have very thick
fluid inside this maybe honey or
something I talk Allah it won't come on
but both case gives you the same cube
for example I will just repeat the same
thing once again so both are two
different liquids in two different
viscosity level and with you throw the
cube in one case if you see the water
came out of the glass another case the
water didn't come onto the glass for the
glass clearly for your reference this
was my glass first case this is my glass
the second case right so let's see this
one teaspoon in one second so just show
you once again so in honey if you see it
drip very story see water this is my
lower is disgusting it is high risk us I
just put a coin on something on an ice
cube if you see its water splashed out
but in this case nothing happened it
didn't even touch here why because the
viscosity is different you must have
seen each nozzle read something if you
put what stoner or ice cube it splash
out but something round splash off is
amber you have a thick mango juice whole
splash up much but if you water normally
this
okay so that's the reason why I'm
studying viscosity because both these
different scenarios happen by because
both this matter had different it gets
costly
okay so if you see milk also if you put
the milk is slash out a little bit so if
you put honey
for example bump in from one planet to
another country you won't even splash
out it will just stick right so
different matter has different viscosity
so we will now understand what is
viscosity viscosity is nothing but is
the measure of resistance to a flow
which arise due to internal friction
between the layers of flame as they slip
past to handle by the liquid so this
pasta is nothing but the resistance to
flow example if I put one bucket of
water it will flow easy right if I put
one bucket of one glass of water in a
fluid it will flow easily but if I put
one in glass of honey it won't flow
easily it you know very slowly why
because the risk the resistance in honey
is more than water since the resistance
is more honey we go slowly so this to
explain this resistance to flow we have
used the term from this case nothing but
resistance to sure right until arrive
through internal friction it in the
layers of fluid and one thing to notice
if let's suppose this is my surface I am
throwing some water or something is
flowing like that right the molecule be
having contact with the surface they are
always stationary this is always
stationary the molecules in contact will
service they always session correct and
the molecules which are the top they'll
have highest velocity will explain that
the velocity tree is
here to here a velocity is zero and this
will have velocity V Max it will
increase in this fashion correct the
molecules in the bottom here will have
the lowest velocity in the molecules at
the surface will have highest colors and
we will see de Rivel relationship on the
house so as I told the velocity of the
lowest molecule will be zero they start
the laminar flow which explains this
concept in more detail it says that the
velocity of the upper layer increases as
the distance from the sixth layer
increases right
this guy has velocity of zero and this
will have velocity of V Max and it will
increase regularly and this type of flow
in rest is a regular gradation of
velocity is regular increasing velocity
and you go from one layer to another it
is called laminar flow this is the layer
is the virtual area assume that there
are different layers of the fluid and we
say that this the velocity of the fluid
therefore when it is in touch to the
ground sir in touching the surface zero
and now the top is matched this kind of
flow is called laminar flow and there is
a regular increasing velocity right so
if the velocity U layer at a distance D
is changed by a value of d u then the
velocity gradient is d u by D Z so here
so let us assume that it had this
velocity U and this had u Plus D u in
this house we managed to three different
layers and this distance is d J so if we
see from here to here the change in
velocity is was do you.why here it was
you here is you guys do machines
velocity is do you and change this is
what DZ so the gradient of change in the
Bella velocity respect to distance will
be D u by D correct see here it was that
suppose you hear it as u Plus D u and
here it is DZ so change in velocity with
respect to D u by D Z right and also
there is a force required to maintain
the flow and this force is proportional
to the area of contact and then
that means I say and force in proportion
to the ER contract in this area and
force inside push me the velocity
gradient dy DZ so if you take both
things into consideration my force is I
will do area into D you by DJ correct
and since it is a promotional thing
we'll make it equal we'll put up so
personally constant corn coefficient of
velocity so I will get something like F
is equal to coefficient constant a by
uniform level correct and this
coefficient of this cos deep is nothing
but measure of viscosity this value
depends on the type of liquid it is if
it is very it will tell whether my
liquid is very viscous or not correct
and the SI unit of this is Newton second
per meter square right on Pascal second
also and unit of coefficient of
viscosity is poised in its number
scientist one poisons are the word one
gram per centimeter per second this is
my laminar flow where I have seen this
velocity is zero this is maximum there
is a gradual increase in velocity and
the velocity layer will be d u by DZ
where it isn't easy and the change in
velocity is do you and the force is
proportional to area of the contact and
also dy Z then so I say that force
exactly we should do a dy DZ
since the proportion we use a
coefficient of viscosity and the growl
will tell you how much this causes
center a particular matter is and it's
SI unit is Newton's second per meter
square and the unit of coefficient
viscosity is poise after a scientist the
lungs are the more modest casa t
viscosity decrease with increase
in temperature quite national diversity
is integration the in perpendicular
force is less and I told viscosity is
nothing but a friction or a position
book flow and this happens because of
intermolecular force so if we increase
the temperature the intermolecular
forces less and thus it flows faster so
viscosity liquid decrease with increase
in temperature we explain that greater
the viscosity slower the liquid flows
because if you saying that viscosity is
more this intermolecular force is more
the friction is more the cohesion to
flow is more and the liquid flow slower
velocity hydrogen bonding and other
wonderful force are the main reason for
high viscosity glass in the liquid form
extremely viscous the so much viscosity
as that it resembles a properly solid
right and if you want to understand the
flow of glass what you can see is you
can see the old panes of a building you
see the wallpaper building the glass you
see it be something like this it will
become thin at the base why because the
gravity and it will the glass close by
close very very slowly maybe centimeter
in years and close like this and you see
the panes see something like this it
will be thicker in the bottom and then
at the top overlapping bit if you see
very old building building which is like
200 years old and this is a glass in
that you see that the glass will not be
equally thick the lower part will be
thicker and the top part will be less
thinner that that you can prove the
viscosity of class is very slow actually
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