Question

Which of the following is correct regarding the formation and collapse of vapor bubbles in a liquid?

(a) Vapor bubbles are formed when the fluid pressure goes above the vapor pressure and collapses when the fluid pressure goes above the bubble pressure

(b) Vapor bubbles are formed when the fluid pressure goes above the vapor pressure and collapses when the fluid pressure goes below the bubble pressure

(c) Vapor bubbles are formed when the fluid pressure drops below the vapor pressure and collapses when the fluid pressure goes below the bubble pressure

(d) Vapor bubbles are formed when the fluid pressure drops below the vapor pressure and collapses when the fluid pressure goes above the bubble pressure

The question was asked during an interview for a job.

The query is from Vapor Pressure topic in division Properties of Fluids of Fluid Mechanics

Answer 1

Right choice is (d) Vapor bubbles are formed when the fluid pressure drops below the vapor pressure and collapses when the fluid pressure goes above the bubble pressure

Easiest explanation: Whenever the absolute pressure of a fluid drops below it’s vapor pressure, bubble formation starts. Again, when the fluid pressure goes above the bubble pressure, it’ll collapse. This is how cavitation formation takes place.