Liquid-in-Glass Thermometer

• The liquid-in-glass thermometer consists of a thin glass bulb joined to a capillary tube with narrow bore which is sealed at its other end.
• The liquid fills the bulb and the adjoining section of the capillary tube.
• When the bulb becomes warmer, the liquid in it expands more than the bulb so some of the liquid in the bulb is forced into the capillary tube.
• The thread of liquid in the capillary tube increases in length.
• The thinner the bulb wall is, the faster the response of the thermometer will be when the temperature changes.
• The liquid used usually contains mercury (or) coloured alcohol.