gas is increased, the volume will increase and push the plunger out. If the gas is cooled, its volume decreases and the plunger moves in. Thus the volume can be used to measure the temperature.
Atmospheric pressure
Piston
Graduated glass syringe
Fixed mass of gas
Rubber cap
Fig 8.5: Gas syringe being kept at constant pressure by varying the volume Resistance
A thermistor (thermal resistor) is a semiconductor whose resistance decreases rapidly with increasing temperature.The resistance of a metal resistor (e.g. platinum) increases with increasing temperature.3
A thermistor Colour
The colour of certain crystals changes with temperature. Liquid crystal thermometers (plastic strip thermometers) which are commonly used to measure body temperature are based on this thermometric property.
A plastic strip thermometer Calibration Curve
A calibration curve is a graph of the thermometric property against temperature, as measured with the laboratory standard thermometer. The new thermometer can be used by noting the value of the thermometric property at an unknown temperature. Then use the graph to find the corresponding temperature.
3Resistance of metals and semiconductors will be dealt with in greater detail in Chapters 18 and 19 respectively.
