Question

The lower end of a capillary tube is at a depth of `12 cm` and water rises `3 cm` in it. The mouth pressure required to blow an air bubble at the lower end will be `x cm` of water column, where `x` is
A. `3`
B. `9`
C. `12`
D. `15`

Answer 1

Correct Answer - D
The lower end of capillary tube is at a depth of `12+3=15cm` from the free surface of water in capillary tube.
So, the pressure required `=15cm` of water column.