Page 1 - Lesson notes-Thermometer

SAI International School
Class VII
Lesson Notes

Subject: Physics
Ch-Heat and Temperature
Subtopic: Thermometer

Thermometer:
The devices that are used to measure temperature are called thermometer.
There are three types of thermometer:
Ø Clinical thermometer
Ø Laboratory thermometer
Ø Digital thermometer

Clinical thermometer:
The thermometer which is used to measure human body temperature is known as
Clinical thermometer.
• The range of clinical thermometer is 35 C to 42 C or 94 F to 108 F.
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• Clinical thermometer has a slight bent just above the mercury bulb which
is known as Kink to prevent the immediate back flow of mercury in the
mercury tube.
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• The normal human body temperature of healthy person is 37 C or 98.6 F
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CONSTRUCTION:
A Clinical thermometer is made up of a long, narrow, cylindrical glass tube which
is sealed at both the ends.
Inside the glass tube there is another thin glass tube and at the lower end is a
bulb which contains mercury.
There is special feature or constriction in the bottom of the glass tube is called
kink.

Precautions should be taken while handling Clinical thermometer such as:
1. It should be washed with antiseptic before and after use.
2. It is made up of glass, should be handled with care.
3. Before using the thermometer, ensure that the level of mercury in
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capillary tube must be below 35 C