Final answer:
To measure one’s temperature, we use thermometers based on Fahrenheit, Celsius, or Kelvin scales. Infrared thermometers offer accurate body temperature readings by measuring infrared radiation. A thermometer must reach thermal equilibrium with the body to provide an accurate measure of its temperature.
Step-by-step explanation:
We measure one’s temperature using devices called thermometers, which come in various forms, such as ear or digital thermometers. These devices are designed according to well-defined scales of measurement: Fahrenheit, Celsius, and Kelvin. Thermometers can be based on different physical principles, including the expansion and contraction of liquids, such as mercury or alcohol, which change dimensions in response to temperature variations. Infrared thermometers are a modern example, which utilize the emission of infrared radiation to directly measure body temperature and are particularly accurate and convenient for medical purposes.
The most common method of measuring body temperature involves placing a thermometer at specific body sites known for reflecting true core body temperature, like the ear canal. These thermometers, especially infrared ones, are accurate and deliver quick readouts. As stated in the zeroth law of thermodynamics, when a thermometer reaches thermal equilibrium with a person’s body, it essentially indicates the person’s body temperature. It’s crucial to follow manufacturer guidelines for using thermometers properly to ensure an accurate reading.
When comparing temperature scales, the Celsius and Fahrenheit are most often used for everyday temperature measurements, while Kelvin is preferred for scientific purposes. The Celsius scale sets the freezing point of water at 0°C and the boiling point at 100°C, whereas Fahrenheit assigns 32°F and 212°F, respectively, to those same reference points.