Answer:
An upper fixed point calibration in a thermometer involves establishing a reference point at the highest temperature that the thermometer can measure accurately. This reference point is typically defined by the boiling point of a pure substance at a specific atmospheric pressure, such as water at standard atmospheric pressure (100°C or 212°F).
To calibrate the thermometer's upper fixed point, the thermometer is first placed in a container of boiling water and allowed to reach thermal equilibrium with the water. The thermometer's reading is then compared to the known boiling point of the substance at that pressure, and any differences are noted. If the thermometer reads higher or lower than the expected boiling point, the thermometer can be adjusted or calibrated accordingly to ensure that it provides accurate temperature readings.
It's important to note that the calibration of a thermometer's upper fixed point should be performed under controlled conditions, as variations in pressure or impurities in the substance being used to establish the reference point can affect the accuracy of the calibration. Additionally, regular recalibration may be necessary to ensure continued accuracy of the thermometer.
Step-by-step explanation: