How does a U-shaped thermometer work?

Answer 1

Otherwise known as a Maximum - Minimum thermometer.

Records the max and min temperature, at the position of a couple of small metal riders.

A u-tube, each arm a few inches long. The lower part of the U contains Mercury, and there will be a small metal bit (a rider) above the mercury in each arm. One of the arms is otherwise filled with alcohol, and the other arm will have a vacuum or alcohol under low pressure.

As the alcohol arm expands, it will depress the mercury column in that arm, and thus elevate the mercury column in the other. The riders are pushed up their respective tubes by the mercury as appropriate. When the temperature changes and the mercury withdraws, the metal bits will remain in position, (by a weak magnet) thus recording the max (or min) temperature in that column.

There is usually a small push button, which moves the weak magnet away from the columns, thus allowing the metal riders to fall to the top of the mercury columns.

The temperature read at both ends of the mercury column (bottom of the riders) should be the same.

Answer 2

A U-shaped thermometer works on the principle of thermal expansion of a liquid. The liquid in the U-shaped tube expands or contracts when the temperature changes, causing its level to rise or fall in one arm relative to the other. This change in level indicates the temperature measurement.

Answer 3

Six's thermometer also called a Maximum minimum thermometer.