Shake the medical thermometer. Why does the reading in the mercury column start to drop?

The reservoir and capillary tube of the medical thermometer are connected by a curved channel of very small diameter. When heated, mercury from the reservoir enters the capillary – the tube opposite the scale. During cooling, the volume of mercury decreases, but it cannot get from the capillary into the reservoir – this is prevented by the narrowing in the channel. This is done so that the thermometer “remembers” the maximum temperature to which it was heated during the measurement. To get mercury from the capillary back into the reservoir, the thermometer must be dispersed several times and suddenly stopped (shaken). Mercury by inertia will pass into the reservoir in portions, the thermometer readings will change.