Question

A one meter long glass tube is open at both ends. One end of the tube is dipped into a mercury cup, the tube is kept vertical and the air is pumped out of the tube by connecting the upper end to a suction pump. Can mercury be pulled up into the pump by this process?

Answer 1

Explanation:

• No, This process does not pull up the mercury in to the pump. The pressure in the upper part gets descended from the atmospheric pressure at the surface of the mercury as the air is sucked into the upper part of the tube by the pump.
• Hence the mercury inside the tube moves in the upward direction towards the lower pressure.  
• Also, the pressure in the tube is balanced by the mercury column. 76 cm is the maximum up to which the mercury can be pulled up.