Question

When a capillary tube is immersed into a liquid, the liquid neither rises nor falls in the capillary. Then,

• A. The angle of contact must be ${90}^{\circ }$
• B. The angle of contact may be ${90}^{\circ }$
• C. The surface tension of the liquid must be zero
• D. The surface tension of the liquid may be zero

Answer 1

Answer: (B), (D)

The surface tension of the liquid may be zero

$h=\frac{2T\cos \theta }{\rho gr}$

So, the angle of contact may be ${90}^{\circ }$ or the surface tension of the liquid may be zero.