Question

Consider a capillary dipped in a liquid in a beaker placed in a cylindrical pis ton arrangement shown in the figure. The height of liquid column in capillary at pressure $P_0$ is h. Now, if the pressure is increased isothermally then h:

• A. increases
• B. decreases
• C. remains the same
• D. nothing can be predicted

Answer 1

Answer: (C)

remains the same

The rise in the tube is due to the surface tension of the fluid, the height h is given by the equation,$h=\frac{2T}{\rho gr}$ If the pressure is increased isothermally,

1) There is no thermal expansion

2) Since the pressure increases both at the top of liquid in the tube as well as at the surface of liquid in the container, the net pressure difference is zero. Hence the liquid level in the tube remains same.