Clinical thermometer A clinical thermometer has a narrow constriction just above the bulb so that when it is removed from the patient the mercury does not fall and it can be read accurately. Also the range is much smaller than in the standard mercury thermometer (Fig 8.2 p. 124).
Infrared radiation thermometer
In this type of thermometer a probe is inserted into the ear. Infrared radiation emitted from the eardrum is detected and a reading of the patient’s temperature is obtained. All hot bodies emit infrared radiation, with the frequency relating to the temperature.This frequency can be picked up by a detector and calibrated to give a reading of temperature. It is considered to be a more accurate method of finding the body’s core temperature than the clinical alcohol thermometer. It is also less invasive and arguably more hygienic.
Other practical thermometers
Many everyday appliances also contain thermometers, e.g. cookers, ovens, boilers and car engines. They can be based on different thermometric properties.
An infrared radiation thermometer
‘SECTION A’ EXPERIMENT QUESTION
Q1 In an experiment to obtain the calibration curve of a thermometer a student placed the thermometer to be calibrated in a beaker of water along with a standard mercury thermometer.The temperature of the water along with thermometric property were measured for different temperatures. The table shows the data recorded.
Table 8.3 Temperature / °C Value of the thermometric property 35
0 16 30 44 60 75 95 46 55 63 74 82 94
(i) Draw a labelled diagram of the apparatus used in the experiment.
(ii) Use the data in the table to draw a graph of temperature against the value of the thermometric property.
(iii) Use your graph to estimate the value of the thermometric property when the temperature is 50C.
(iv) State a precaution that could have been taken in this experiment to ensure its accuracy.
(v) Name a thermometric property that could have been used in this experiment. How would the value of this thermometric property have been measured?
