تسجيل الدخول

تسجيل

Maximum and Minimum Thermometers

المؤلف:  GEORGE A. HOADLEY

المصدر:  ESSENTIALS OF PHYSICS

الجزء والصفحة:  P-244

2025-11-23

626

Thermometers are used by the stations of the Weather Bureau to show the highest and lowest temperatures during each day. One form of maximum instrument is made like the clinical thermometer. After being read it is set by swinging it around in a circle, so that the centrifugal force drives the mercury back into the bulb, and the instrument is then ready for the next day. One form of minimum thermometer is an alcohol thermometer with a small glass spool or index moving loosely in the tube. This is drawn down by surface tension whenever the end of the liquid column touches the end of the spool as the liquid contracts; but when it expands, the liquid runs past the spool and leaves it at the point of lowest temperature. To set this thermometer it is merely necessary to tip the tube slightly, and the spool will run to the end of the liquid column and stop.

FIG. 1. - Minimum and Maximum Thermometers