Capillary Action

Q.

The pressure of air in a soap bubble of 0.7cm diameter is 8 mm of water above the pressure outside. The surface tension of the soap solution is

1. 150 dyne/cm

2. 137 dyne/cm

3. 100 dyne/cm

4. 68.66 dyne/cm

Q. A wooden cube just floats inside water when a 0.2 kg mass is placed on it .When the mass is removed, the cube is 2 cm above the water level , what is the size of the cube

Q. the change in surface energy when a drop of radius R splits up into 1000 droplets each of radius r is (surface Tension is T)

Q.

Nature of meniscus for liquid of $0^{\circ }$ angle of contact

1. Cylindrical

2. Plane

3. Parabolic

4. Semi-spherical

Q. What is Capillarity Derive an expression for the rise of liquid in a capillary tube. (3M)

Q.

Soap helps in cleaning clothes, because

1. Chemicals of soap change

2. It increases the surface tension of the solution

3. It lowers the surface tension of the solution

4. It absorbs the dirt

Q. a body cools down from 45^° C to 40^° C in 5minutes and to35^° C in anothr 8min. find temp of surroundin

Q.

There is an air bubble of radius 1.0 mm in a liquid of surface tension 0.075 Nm^-1 and density 1000 kg m^-3. The bubble is at a depth of 10 cm below the free surface. By what amount is the pressure inside the bubble greater than the atmospheric pressure? Take g = 9.8 m s^-2.

1. 980 Pa

2. 1260 Pa

3. 2260 N/m²

4. 1130 N/m²

Q.

Two capillary tubes of same diameter are put vertically one each in two liquids whose relative densities are 0.8 and 0.6 and surface tensions are 60 and 50 dyne/cm respectively. Ratio of heights of liquids in the two tubes $\frac{h_1}{h_2}$ is

1. 

2. 

3. 

4. 

Q. It is difficult to fill a capillary tube with mercury than with water since:

1. Angle of contact between glass & mercury is more than ${90}^{\circ }$ and the angle of contact between glass and water is less than ${90}^{\circ }$.
2. Angle of contact between glass and mercury is less than ${90}^{\circ }$ and the angle of contact between glass and water is more than ${90}^{\circ }$.
3. Angle of contact is same for both water and mercury.
4. Mercury is less dense than water.

Q.

The spiders and insects move and run about on the surface of water without sinking because

1. Spiders and insects are lighter

2. Elastic membrane is formed on water due to property of surface tension

3. Spiders and insects swim on water

4. Spider and insects experience upthrust

Q. Water rises in plant fibres due to

1. capillarity
2. viscosity
3. fluid pressure
4. osmosis

Q.

The adjoining diagram shows three soap bubbles A, B and C prepared by blowing the capillary tube fitted with stop cocks, $S_1$, $S_2$ and $S_3$. With stop cock S closed and stop cocks $S_1$, $S_2$ and $S_3$ opened

[CPMT 1988]

1. B will start collapsing with volumes of A and C ncreasing

2. C will start collapsing with volumes of A and B increasing

3. C and A both will start collapsing with the volume of B increasing

4. Volumes of A, B and C will become equal at equilibrium

Q. An air bubble inside a liquid surface tension 1*10^-3 nm grows from a radius of 1.0*10^-5 to 1*10^-4 in 6 meus the average rate od change of the pressure inside the bubble is

Q.

Two capillaries made of the same material with radii $r_1$=1mm and $r_2$=2mm. The rise of the liquid in one capillary ($r_1$=1mm) is 30 cm, then the rise in the other will be

1. 7.5 cm

2. 60 cm

3. 15 cm

4. 120 cm

Q. An object of specific gravity σ is hung from a massless string .The tension in string is T.The object is immersed in water so that one half of its volume is submerged .The new tension in the string is .

Q. A small soap bubble of radius 4 cm is trapped inside another bubble of radius6 cm without any contact. Let P2 be thepressure inside the inner bubble and P be the pressure outside the outer bubble .Then Radius of another bubble with pressure difference P2-P between its inside andoutside would be:

Q. 23.Why the pressure inside a capillary tube is Patm-2sigma/r

Q. The meniscus of water in silver tube is .

1. concave
2. plane
3. convex

Q. A vertical glass capillary tube open at both ends contains some water. Which of the following shapes may be taken by the water in the tube

1. 

2. 

3. 

4. 

Q. 77. An object have specific gravity p is hung from massless string. The tension in the string is T. The object is immersed in water so that one half of its volume is submerged. The new tension in the string is ?

Q.

Due to capillary action, a liquid will rise in a tube, if the angle of contact is

1. Acute

2. Obtuse

3. ${90}^{\circ }$

4. Zero

Q. a capillary tube is dipped in water and it is 20 cm outside water. the water rises upto 8 cm . if the entire arrangement is put in freely falling elevator the length of water column in the capillary tube will be ??

Q. A glass capillary tube of internal radius $r=0.25\text{mm}$ is immersed in water. The top end of the tube projects by $2\text{cm}$ above the surface of water. At what angle does the liquid meet the ends of the tube?
[surface tension of water = $0.07\text{N}{\text{m}}^{-1}$]

1. ${60}^{\circ }$
2. $0^{\circ }$
3. ${70}^{\circ }$
4. ${180}^{\circ }$

Q. A capillary tube of diameter $1\times {10}^{-3}\text{m}$ is dipped in a container containing water. Given the surface tension of water is $0.072\frac{\text{N}}{\text{m}}$ and angle of contact is $0^{\circ }$, choose the correct option(s).

1. The liquid level in the capillary will be more than that in the container.
2. The liquid level in the capillary will be less than that in the container.
3. The capillary rise will be $2.94\times {10}^{-2}\text{m}$.
4. The capillary drop will be $1.14\times {10}^{-2}\text{m}$.

Q.

The pressure of water at the bottom of a water tank exceeds the atmospheric pressure by 10⁴ Pascal. The velocity of efflux of water through an orifice at the bottom of the water tank will be (g = 10 ms^-2).

1. 

2. 

3. 

4. 

Q. In order to make an object float in a fluid. Its weight should be equal to

Q. A rectangular film of liquid is extended from (4×2 cm) to (5×4cm) . If the work done is 0.0003J the value of surface tension is? How to calculate the no. Of sides of rectangle exposed?

Q. Mercury has an angle of contact equal to 140° with soda lime glass. A narrow tube of radius 1.00 mm made of this glass is dipped in a trough containing mercury. By what amount does the mercury dip down in the tube relative to the liquid surface outside ? Surface tension of mercury at the temperature of the experiment is 0.465 N m¯¹Density of mercury = 13.6 × 103 kg m¯³

Q. A cylindrical tube of uniform cross-secional area A is fitted with two air tight frictionless pistons. The pistons are connected each other by, a metallic wire. Initially, the pressure of the gas is po and temperature isT atmospheric pressure is also Po Now, thelemperatnre of the gas is increased to 2T, the tension of wire will be