Measuring Temperature: Maximum and Minimum Thermometers Video Lecture | Class 7 Oxford Science: Chapter Notes, Worksheets & Tests

hello friends this video on whether
climate and adaptations part four is
brought to you by example calm
no more fear from exam so let us discuss
about each of these elements in little
more details so we will first talk about
temperature now how do we measure the
temperature of the environment like we
are saying that okay when it is summer
the temperature is more and when it is
winter the temperature is less similarly
we said that during the early morning
the temperature goes low that's why we
heat old but by the time it is afternoon
it's like white he white hot and the
temperature becomes high now how do we
know how much is the temperature so for
that purpose we have this device called
maximum and minimum thermometers so
these are special type of thermometers
which have been designed to measure the
temperature of the environment like we
are all familiar with a thermometer we
know what is a thermometer so it's like
a glass tube your bitch has some mercury
inside it and it has a scale which is
graduated with radius values and when we
put it in our body it tells the
temperature of our body so that
thermometer is a clinical thermometer we
have learnt:about thermometers and one
of our previous lesson read so we often
use thermometer when you fall ill when
we are high with fever we want to
imagine our body temperature so this is
also a thermometer which is which again
consists of glass tube with graduations
on it which help you to note the
temperature but it is little differently
designed so that it can measure the
temperature of the atmosphere so let us
have a look at this special type of
thermometer so this is how maximum and
minimum thermometer looks like so you
see it has got two scales instead of one
like for the normal thermometer which is
used to measure body temperature it just
have one scale but here you have two
different scales it's like kind of a
u-shaped tube so the glass tube is
u-shaped so what does this thermometer
do what is
speciality of the thermometer it is
going to record the highest and the
lowest temperature during a period of
time so let us say if you want to know
which was what was I this temperature on
a particular day and what was the lowest
temperature so this thermometer would be
your best choice so that that's what I
was telling you right then I showed you
the newspaper clippings so in the
newspaper clippings it told the maximum
and minimum temperature for each
particular location like for Bangalore
it showed the maximum and minimum
temperature for Delhi it should maximum
and minimum temperature and similarly it
showed it for all other places so how we
recorded that temperature is using a
maximum and minimum thermometer so let
us learn more about maximum and minimum
thermometers so here you can see the
picture more clearly that it has got a
u-shaped glass tube so you see this is
the u-shaped glass - it is in the shape
of the English alphabet you write so and
in this u-shaped glass tube on both the
sides you have to separate temperature
scales along each arc of the U so if
this is your u this is one temperature
scale and this is another temperature
scale so one of these will measure the
maximum temperature the other one will
measure the minimum temperature and both
these arms so this is one arm this is
the other arm both is arm they terminate
in a sealed glass tube so on the other
end it is not open but there is it it is
sealed on the other end and which is the
liquid present inside maximum and
minimum thermometer like mostly in
clinical thermometers mercury is present
because of so many characteristics like
it does not stick to the walls it has a
high melting point it has a shiny
appearance now in these thermometers
marketing is not used because there are
certain disadvantages also which are
associated with mercury light it is very
difficult to dispose of library because
it is extremely poisonous
so in these thermometers marker
replaced by alcohol because alcohol has
a lot of properties which are similar
but pretty but at the same time it
doesn't have these advantages which are
therefore martini
so basically this is how the
construction of the maximum and minimum
thermometers are so if you look at these
two separate scales so you can very
clearly see that in one scale so it is
in the increasing order towards this
site whereas on the other scale it is
just the opposite the values are
increasing along the side so it is
something like this so here on this
scale the more the column moves up by
measuring temperature that what would
happen and what would happen if it goes
high on this key so on if on this case
the van it is going up the value is
actually decreasing but in this scale if
it is going up the value is actually
increasing so that is the beauty of
having two arms and each arm has the
labeling in the opposite sense so two
temperature scales exist so this is one
temperature scale this is another
temperature scale so one records maximum
temperature whereas the other records
minimum temperature so you can have a
close look on the maximum and minimum
thermometer so you see the terminal ends
of the thermometer they terminate in
sealed glass bulbs and also the two
different scales one of them is for
Maxima the other one is for minima so
you see as the liquid rises on this tube
it gives you the reading of minima and
the rinds of liquid in this tube gives
you the reading for maximum temperature
so that's how the thermometer measures
maximum and minimum temperatures
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