The radius of the bore of a capillary tube is $r$ and the angle of contact of the liquid is $\theta$. When the tube is dipped in the liquid,the radius of curvature of the meniscus of liquid rising in the tube is

Two capillary tubes of same diameter are kept vertically in two liquids whose densities are in the ratio $4:3$. If their surface tensions are in the ratio $6:5$,the ratio of heights $\left(\frac{h_1}{h_2}\right)$ of liquids in the two capillary tubes is (Their angle of contacts are same).

The kerosene oil rises up in the wick of a lamp ...........

Give reason: The lighting of a lamp is due to the wick of the lamp.

$A$ glass capillary tube of inner diameter $0.28 \,mm$ is lowered vertically into water in a vessel. The pressure to be applied on the water in the capillary tube so that the water level in the tube is the same as that in the vessel is ............ $\times 10^3 \,N/m^2$ (surface tension of water $= 0.07 \,N/m$ and atmospheric pressure $= 10^5 \,N/m^2$).

Water rises to a height of $20 \,mm$ in a capillary tube of cross-sectional area $A$. If the area of cross-section of the tube is made $\frac{A}{4}$, then water will rise to a height of (in $\,cm$)