Question

When a capillary tube is connected to a pressure head V.c.c. of water flows per second. If another tube of same length but half the radius is connected to the first in series to the same pressure head, the quantity of water flowing through them per second will be ( in c.c):

• A. $\frac{V}{16}$
• B. $\frac{V}{17}$
• C. $\frac{17V}{16}$
• D. V

Answer 1

The correct option is B $\frac{V}{17}$

$V=\frac{\pi P{r}^4}{8\mu l}$

$V_1=\frac{\pi P_1(r{)}^4}{8\mu l}$

flow will be same through both tube.

$V_1=\frac{\pi P_2(r/2{)}^4}{8\mu l}$ now $radiusis=r/2$ ......(1)

And $P_1+P_2=P$

from above three equation we get

$P_2=16P/17$

putting this in equation 1 we get

$V_1=V/17$