What Is The Principle Of How A Mercury Thermometer Works?

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Samuel Chiltern answered
The Basic Principle of a Mercury Thermometer
All thermometers work on the principle that warm fluids occupy more space than cold fluids.

Since we know how much space a fluid such as mercury will fill at any given temperature, we are therefore able to determine the temperature of that fluid by measuring how much space it takes up.

The total internal volume of the thermometer tube is precisely engineered, and the thermometer casing carries a series of markers - which indicate the temperature of the liquid to the person using the apparatus.

Why Mercury?
A scientific explanation is that the volume of a fluid is proportional to its temperature, although of course many fluids have differing densities, and so will take up differing amounts of space at
the same temperature.

To add to the potential for confusion, not all fluids expand in a linear fashion, which makes it more difficult to use them for measuring temperature accurately.

Mercury is the only metal which is a liquid at room temperature, and it is also a poor conductor of heat.

It is known to have a high co-efficient of expansion - which basically means that even relatively minor changes in heat will be reflected by a change in the fluid's volume.

The expansion characteristics of mercury are relatively linear compared with many other liquids, meaning that it is possible for it to provide accurate temperature readings.

Mercury has a high boiling point, due to its high density. This makes it suitable for taking readings at high temperatures, which makes mercury thermometers especially useful in laboratory settings.

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