Excess Pressure Inside a Soap Bubble (ΔP = Pi − Po = 4S/r)
jee-mainjee-advancedneet-ug
ΔP = Pi − Po = 4S/r
What each symbol means
| Symbol | What it stands for |
|---|---|
| S | Surface tension of the soap solution (N/m) |
| r | Radius of the soap bubble (m) |
| Pi | Pressure inside the soap bubble (Pa) |
| Po | Pressure outside the soap bubble (Pa) |
| ΔP | Excess pressure inside the bubble over outside (Pa) |
When to use this
For a soap bubble (or any thin-walled bubble with TWO liquid-air interfaces). Factor of 4 instead of 2 because a soap bubble has two surfaces (inner and outer). For an air bubble inside a liquid, use 2S/r (only one interface).