7.12 Effect of Structure of a Liquid-in-Glass Thermometer on Its Sensitivity, Range, and Linearity

The structure of a liquid-in-glass thermometer affects its sensitivity, range, and linearity in the following ways:

7.12.1 Effect of Diameter of Tube on Sensitivity of Thermometer

Sensitivity of a thermometer is its ability to detect the smallest change in temperature. Liquid-in-glass thermometers have a long capillary tube of small diameter filled with liquid mercury or alcohol. The sensitivity of a liquid-in-glass thermometer is affected by the diameter of this tube. A thermometer with a small diameter capillary tube can detect smaller changes in temperature than one with a large diameter tube. A narrower diameter tube contains a smaller volume of liquid, which reacts quickly to absorbed heat and rises more rapidly.

7.12.2 Effect of Nature of Liquid Used in Thermometer on Its Sensitivity

Liquids like mercury and alcohol expand more than others when heated, compared to liquids like water. Therefore, thermometers containing mercury or alcohol are more sensitive to temperature changes.

7.12.3 Effect of Size of Bulb of Thermometer on Its Range

The range of a liquid-in-glass thermometer is affected by the volume of the bulb. A larger bulb holds more liquid, allowing for greater expansion, which results in a thermometer with a wider temperature range.

7.12.4 Effect of Nature of Liquid Used in Thermometer on Its Range

Mercury is often used in thermometers due to its low melting point and high boiling point, providing a wide range of temperature measurement. Liquids with a broader boiling point range offer a wider range than those with a narrower boiling point range.

7.12.5 Effect of Type of Glass Used in Thermometer on Its Linearity

The type of glass used in a thermometer can affect its linearity. Factors like expansion and contraction, transparency, chemical stability, uniformity, durability, and thermal conductivity of the glass impact this property. For example, borosilicate glass, with its more linear expansion coefficient, results in a thermometer that is more linear compared to one made with soda lime glass.