Question

Two soap bubbles $A$ and $B$ are formed at the two open ends of a tube. The bubble $A$ is smaller than bubble $B$. If valve $V$ is opened and air can flow freely between the bubbles, then

• A. There is no change in the size of the bubbles
• B. The two bubbles will become of equal size
• C. $A$ will become smaller and $B$ will become larger
• D. $B$ will become smaller and $A$ will become larger

Answer 1

The correct option is C $A$ will become smaller and $B$ will become larger

Excess of pressure inside the bubble, $P=4S/r$.
So smaller is the radius $r$, the larger is the excess of pressure $P$. It means, the pressure of air is more in bubble $A$ than in bubble $B$. So the air will go from bubble $A$ to bubble $B$.