Question

A capillary tube C dipped in a liquid that wets it as shown in figure. If we blow air through the horizontal tube H, then what will happen to the liquid column in the capillary tube ?

• A. Level will fall below A
• B. Level will rise above A
• C. Level will remain at A
• D. It is difficult to predict

Answer 1

The correct option is B Level will rise above A

Bernouli's principle gives us the relation for a fluid flowing as:
$P+\frac{1}{2}\rho v^2=constant$
Although this equation is not exactly valid in this case (need to specify ideal fluid flow)
It gives us an idea as to how the pressure would behave.
If air is blown, the pressure would drop, more liquid would get sucked up.
The capillary would rise above A.