Question:

Under a constant pressure head, the rate of flow of orderly volume flow of liquid through a capillary tube is $V$. If the length of the capillary is doubled and the diameter of the bore is halved, the rate of flow would become

Updated On: May 12, 2024
  • $V / 4$
  • $V / 8$
  • $16 V$
  • $V /32$
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The Correct Option is D

Solution and Explanation

According to Poiseuille's formula, rate of flow through a narrow tube $V = \frac{\pi Pr^4}{8 \eta l}$
For given $P$ and $\eta , V \propto \frac{r^4}{l} \therefore \:\: \frac{V_1}{V_2} = \frac{r^4_1}{r_2^4} \times \frac{l_2}{l_1}$
,
Here, $V_1 = V, r_2 = r_1 /2 , l_2 = 2l_1, V_2 = ?$
So, $\frac{V}{V_2} = (2)^4 \times 2 = 32 , V_2 = \frac{V}{32}$
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Concepts Used:

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The science of the mechanical properties of fluids is called Hydrostatics. A fluid is a substance that relents to the slightest pressure. Fluids are categorized into two classes famed by the names of liquids, and elastic fluids or gases, which later comprehend the air of the atmosphere and all the different kinds of air with which chemistry makes us acquainted.

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Tube of Flow:

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Surface Tension and Viscosity:

The surface tension of a liquid is all the time a function of the solid or fluid with which the liquid is in contact. If a value for surface tension is provided in a table for oil, water, mercury, or whatever, and the contacting fluid is unspecified, it is safe to consider that the contacting fluid is air.