Question

_______ is used when ink is filled in a Chinese ink pen.
A. Pumping action
B. Motor action
C. Surface tension
D. Gravity

Answer 1

Here in this question the concept of Bernoulli’s principle is used.Theorem states that for a steady flow of an incompressible and non-viscous liquid the sum of the pressure, kinetic energy per unit volume and potential energy per unit volume remains constant through the flow.

Complete answer:
As we said, it works on the principle of Bernoulli’s theorem.
Where, $P + \dfrac{1}{2}\rho {v^2} + \rho gh = {\text{ constant}}$, $p = {\text{ pressure}}$ and $\rho gh = {\text{ potential energy}}$.
First, we place the ink dropper inside the ink bottle to fill the ink in the ink dropper. As we press the rubber of the ink dropper, the air moves outside and ink is collected in the ink tube. The ink collected in the ink dropper is used to fill the ink pen. The ink dropper actually works on Bernoulli's principle.

When we place the ink dropper inside the ink pen and press the rubber of the dropper, high pressure is created inside the tube of the ink dropper. Due to the pressure difference created, the ink moves into the ink pen. But when we place the ink dropper inside the ink bottle, we release the rubber which in turn increases the area.

The increase in area decreases the pressure inside the tube, then ink moves from higher pressure to lower pressure. Hence the ink rises in the tube from the ink bottle just because of lower pressure inside the tube due to an increase in area. The ink from the ink dropper never falls due to gravity, it falls only when we press the rubber section of the ink dropper. This is only due to the very small opening of the dropper tube which keeps surface tension of liquid inside the tube very high.

This high surface tension doesn't allow the liquid to fall due to gravity but when we apply pressure at the rubber section then liquid falls. The pressure inside the tube can be calculated by Pascal's law, The pressure of the liquid inside the tube is much less than the atmospheric pressure, so the liquid stays inside the tube which is a low-pressure area.

Therefore, the correct answer is option A.

Note: In this question, students have the knowledge of the term surface tension, pressure, atmospheric pressure, gravity, pascal’s law and mainly Bernoulli’s theorem to solve this question correctly and accurately.Pascal’s Law states that pressure exerted in some liquid which is at rest is the same in all directions i.e., pumping action is used when ink is filled with a Chinese ink pen.