Mercury Thermometer is a device used to measure the hotness or coldness of the body. In other words, it is a device to measure body temperature. Mercury Thermometer is very common in labs. Mercury plays major role in the calculation of temperature in this device.
Working Method of Mercury Thermometer:
The lower end of thermometer contains a glass bulb which is full of mercury liquid. The glass bulb is connected to the thin capillary tube in the glass rod. When the thermometer is kept in contact with object or body the temperature increases in the glass bulb of Mercury Thermometer. When temperature increased, the mercury expands in capillary tube. Though the volume of glass bulb and mercury both increases because of heat. The rate of expansion of mercury is much more greater than that of glass bulb. As the expansion of mercury is high it force to expand in the tube as the temperature increases.
Advantages of Mercury Thermometer:
- Its boiling point is 357* C and freezing point is -39* C. Therefore, it can be used over a wide range of temperature.
- Its expansion is nearly uniform over the ordinary range of temperatures. This makes the calibration of the thermometer easier.
- Mercury can be easily seen through the glass because of its opaque and shining property.
- It does not wet the glass and can be easily obtained in the pure state.
- It has low specific heat, so it does not take much heat from the body whose temperature is to be measured.
Disadvantages of Mercury Thermometer:
- Mercury thermometer cannot measure temperature below -39* C and above 357* C. So, in the Artic and the Antartic region, this thermometer cannot be used.
- Because of fast expansion, there might not be accurate meter reading.
- The vapor of Mercury is very poisonous to human beings.
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