Why the Mercury-in-glass thermometer first descends and then rise when put in flame?

Answer 1

When placed in a flame, the glass bulb expands rapidly. This increases the volume of the bulb and so the column descends. However, the glass then conducts the heat to the Mercury so that it undergoes thermal expansion and the column rises.

Answer 2

If the heat is applied suddenly to the glass bulb containing the mercury reservoir, it is possible that the bulb could expand before the mercury is heated. This could cause the level of mercury to fall briefly.

Answer 3

Because the glass that makes up the thermometer heats up first and expands thus making more room for the mercury which will fall before it heats up and expands

Answer 4

Because unlike other materials, mercury expands when heated.

Answer 5

When a mercury thermometer put in flame, we observe that mercury first descends, because first the internal volume of the capillary tube increases, which cause the mercury first descends.

Answer 6

The mercury in the thermometer's tube expands and contracts due to the surrounding temperature. As the mercury is inside a narrow tube, it can only expand upwards, and contract downwards.

Answer 7

It first descends because expansion of the capillary bore and bulb takes place.

Soon after that, the mercury absorbs the heat and expand, causing the mercury column to rise.

Answer 8

The metal expands when hot, and rises. It contracts when cool.