How exactly does a thermometer work?

Question

I mean I know it gages the temp. but how?

Answer 1

for example a mercury thermometer relies on the principle that mercury occupies a larger volume when its temperature is increased, and the rate at which the volume increases is a direct relation to the temperature. Hence a scale can be drawn up and temperature can be measured via mercury expanding along a small cylindrical pipe (thermometer).

This is only one type, and is not as accurate as others.

Answer 2

There are many kinds of thermometers that work in many different ways.

http://en.wikipedia.org/wiki/Thermometer...

Here's the one you're probably considering:

http://en.wikipedia.org/wiki/Mercury-in-...

Answer 3

the mercury in the thermometer expands as it gets warmer which forces it up the thermometer