What is a thermometer?
The word 'thermometer' is derived from two smaller Greek words - 'thermos' which means warm and 'meter' which means to measure. It is a device used to measure temperature.The traditional thermometer is based on expansion and contraction of mercury. There is a bulb attached to a tube and the bulb is filled with mercury. The neck close to the bulb is narrowed and with a rise in temperature the mercury in the bulb rises due to expansion. Mercury goes up the tube. But with the lowering of temperature, the mercury level falls and breaks at the narrowed portion, remaining in the tube.