Thermometer is a device by which we can measure temperature of a body.
Types of thermometer:
1. Clinical thermometer: Clinical thermometer is used by a doctor to take the temperature of human body.
A clinical thermometer can only measure a temperature of range 35°C to 43°C. Because the normal temperature of a human body is 37°C and it never drop to 35°C and can’t rises to 43°C unless certain drastic condition reached.
2. Laboratory thermometer: Laboratory thermometers are used to measure temperature in any chemical reaction or observation. It has a tempture range of -10°C to 110°C.
3. Maximum-minimum thermometer: These type of thermometer are only use to measure the maximum and minimum temperature of a day.
How to differentiate clinical and Laboratory thermometer?
A clinical thermometer is just same as a laboratory thermometer but has a slight “bent” or “kink” in the capillary tube just above the bulb. To check the body temperature, the thermometer is normally placed in the mouth. The mercury in the bulb expands according to the temperature in the mouth and its level increases in the capillary tube. We take out the thermometer from the mouth and read the marking on the scale to know our body temperature.
Why does the temperature in the clinical thermometer not drop when it taken out of the mouth?
When the thermometer is taken out of the mouth the mercury in the bulb contracts as temperature outside our body is normally less, and the mercury column breaks at the kink. Thus the level of the mercury remains constant even after taking the thermometer out of the mouth.
The mercury in the stem is bought back to the bulb by giving a few soft jerks with the our hands before the thermometer is used again.
Mercury is toxic in nature. If a thermometer breaks it is difficult to dispose of the mercury. So nowadays mercury thermometer are being replaced by digital thermometer that does not use mercury.
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Technology 19
