Torricelli's barometer experiment

Steps:

• Fill a long, closed tube completely with mercury and seal the open end.
• Invert the tube into a dish of mercury, allowing the open end to submerge.
• Mercury partially flows out, creating a vacuum space at the top of the tube.
• The column height stabilizes at 76 cm, balanced by atmospheric pressure.

Why C is correct:

• C describes the formation of a Torricellian vacuum above the mercury, where atmospheric pressure (1 atm) supports a 76 cm column, as defined by the barometer principle.

Why the others are wrong:

• A: Mercury does not fall out completely; atmospheric pressure holds the column.
• B: The tube does not remain full; partial outflow creates the vacuum.
• D: Levels do not equalize; lower pressure inside the tube maintains the height difference.

Final answer: C