 physics channel for physics please subscribe my channel hello everyone before the video watch it first come on man no need to be scared with this it is simple a thermal scanner same like a thermometer and other devices which are used to measure temperature so what is a thermometer a thermometer the device that measures temperature the degree of hotness and coldness of substance there are three temperature scales in use today Fahrenheit Celsius and Kelvin this is a liquid in thermometer there is a mercury inside and you can see the red color if you look at the reading it is 23 I guess the length of this thermometer is called the stem of thermometer and you can see the range is after 100 there is 10 more places if you come back to the thermometer you can find before 0 also there is 10 more it means the range of this thermometer is minus 10 degree Celsius to 110 degree Celsius let's talk about two important terms here to fixing our temperature scale one is called lower fixed point and one is called upper fixed point we need to make two standard points here the lower fixed point as you can see on the screen is 0 degree Celsius whereas the upper fixed point is 100 degree Celsius let's talk about some more terms related to thermometers for example sensitivity thermometer whose liquid expands more due to a slight change in temperature are more sensitive the narrower that you the higher the sensitivity of the thermometer range range means the minimum and the maximum measure by the thermometer if you remember the last slide we studied that the minimum was minus 10 degree Celsius and the maximum was 110 degree Celsius responsiveness a thermometer with a larger ball takes longer to response to temperature changes similarly what is linearity a thermometer should respond to temperature change uniformly it means the thickness of the thermometer where the mercury is there should remain same let's talk about the structure of thermometer this is a liquid in glass thermometer with long narrow tube there is a bulb here and mercury inside and it's contained a same thickness so what do you think what is a normal temperature of body it is 37 degree Celsius it means this normal temperature in between 35 degree Celsius to 42 degree Celsius so the normal temperature of human body is 37 which started from 35 till 42 okay so let's talk about the unit of temperature the unit of temperature here is degree Celsius this is the unit of temperature here let's have a look closely this is a capillary tube and the if you provide some heat to the thermometer the mercury start moving from left to right quickly while there is a bend here the bend is to prevent the flow of mercury back towards its original and you get time to read the temperature on the thermometer so you can see here closely there are 10 divisions between 36 and 37 so these 10 divisions shows that each one is 0.1 it means 36.1234 so the reading is 36.4 but in some thermometers there are five divisions also one over five means 0.2 degree Celsius