Mercury columns are used to measure which of the following?

Mercury columns are specifically used to measure vacuum pressure. This is due to the physical properties of mercury, particularly its density and the way it behaves in a tube, which allows it to create a clear measurement scale for the pressure exerted by gases. In a vacuum system, mercury can effectively indicate how much pressure is being removed from a space, allowing for precise readings in various industrial and scientific applications.

The use of mercury in columns is advantageous as it can create a significant height difference, providing a wide range of measurement capability for low pressures, which further supports its effectiveness in vacuum applications.