Surface Tension MCQ Quiz in मल्याळम - Objective Question with Answer for Surface Tension - സൗജന്യ PDF ഡൗൺലോഡ് ചെയ്യുക

ConceptL

Surface tension (S):

• It is the property by virtue of which the free surface of a liquid at rest behaves like an elastic stretched membrane tending to contract so as to occupy the minimum surface area.
• Surface tension is measured as the force acting per unit length of an imaginary line drawn on the liquid surface.

Surface tension (S) = \(\frac{Force}{length}\)

Surface energy is given by:

Surface energy (U) = S × (Δ A)

where Δ A is the change in area

Calculation:

Given that,

Radius = R

Area = 4πR² 

Surface tension = s

Surface energy (U) = S × (Δ A)

Surface energy (U) = s x 4πR2 

Surface energy (U) = 4πR2s

Surface tension: 

• Surface tension is the property by virtue of which liquid tries to minimize its free surface area.
• In a spherical shape the surface area is minimum and for this reason, the raindrops are spherical.
• Surface tension is measured as the force acting per unit length of an imaginary line drawn on the liquid surface.

\(Surface\;tension = \frac{{Force}}{{length}}\)

Calculation:

Given:

Surface tension (σ) = 3 × 10-2 N/m, length of the film (l) = 10 cm = 0.1 m

Surface tension force for one film of soap bubble (F) = σ × l = 3 × 10^-2 × 0.1 = 3 × 10-3 N

Now, the weight of the straw will be balanced by surface tension force.

Let the mass of the straw be m, then

mg = 2 × F    (we have used 2 here because there are 2 films forms in soap bubble)

m × 10 = 2 × 3 × 10-3

\(m=\frac{6× 10^{-3}}{10} \)

m = 0.6 × 10^-3 kg = 0.6 gm

The angle of contact between a solid and liquid is the angle between the tangent of liquid surface and tangent of the solid surface. The tangents are drawn from the point of contact of liquid with the solid.

Angle of contact depends upon the nature of the liquid and solid contact and the medium which exists above the free surface of liquid.

Surface Tension:

• It is defined as force per unit length in the plane of the liquid surface at right angles to either side of an imaginary line drawn to the surface.
• \(Surface\;Tension = \frac{{Force}}{{Length}}\)
• An unbalanced force is developed at the interface stretched over the entire fluid mass. 

Variation of surface tension of water with temperature:

Concept:

Surface Tension:

• When a liquid is exposed to the air, it behaves like a stretched membrane as the water molecules are attracted to each other. This property of liquid is also called Surface tension.
• At liquid-air interfaces, surface tension results from the attraction of water molecules to each other, which is a cohesive force, then to the molecules in the air, which is an adhesive/repulsive force.
• The combined effect of these two forces is an inward force at the surface of the liquid which causes the surface to behave as if it were covered with a stretched elastic membrane.

Hence, the phenomenon due to which the exposed liquid behaves like a stretched membrane is called surface tension.

Additional Information

• Surface tension has the dimension of force per unit length, or energy per unit area is only defined for Newtonian liquids.
• While cohesion and adhesion forces play a role in membrane formation, it is their combined effect which is called surface tension that is considered to be the cause of the formation of the stretched membrane.
• Capillary action is also an effect of surface tension that is only applicable to small tubes that contain liquids.

Concept:

Pressure difference in soap bubble is given by

\({\bf{Δ P}} = \frac{{8{\bf{σ }}}}{{\bf{d}}}\)

where ΔP = Pressure difference of inside and outside of the bubble, σ = Surface tension of the fluid, d = diameter of the sphere.

Calculation:

Given:

ΔP = 16 N/m², d = 3 mm, σ = ?

Now, we know that

For soap bubble

\({\bf{\Delta P}} = \frac{{8{\bf{\sigma }}}}{{\bf{d}}} \)

\(\sigma =\frac{\Delta P\times d}{8}= \frac{{16\; \times \;3\; \times \;\;{{10}^{ - 3}}}}{8} = \;6\; \times \;\;{10^{ - 3}}\;{\bf{N}}/{\bf{m}}\)

Concept:

Pressure inside a water drop is given by:

\(Δ P = \frac{{4T}}{D}\)

where T = surface tension and d = diameter of water drop

Given:

Diameter (D) = 0.001 m, surface tension (T) = 0.072 N/m

Since the air bubble is immersed in water, there will be only one interface. So the formula for liquid droplet is applicable.

\(Δ P = \frac{{4T}}{D} = \frac{{4 \times 0.072}}{{0.001}}\)

⇒ ΔP = 288 N/m²

The formula for pressure inside soap bubble (2 surfaces) is

\({\rm{\Delta }}P = \frac{{8T}}{D}\)

The formula for pressure inside liquid jet is

\({\rm{\Delta }}P = \frac{{2T}}{D}\)

Explanation:

Surface Tension:

• It is defined as force per unit length in the plane of the liquid surface at right angles to either side of an imaginary line drawn to the surface.
• Mathematically, 
• \(Surface\;Tension = \frac{{Force}}{{Length}}\)
• An unbalanced force is developed at the interface stretched over the entire fluid mass. 
• It is the tendency of the liquid surface to shrink into a minimum surface area.
• The SI Unit of surface tension is N m-1
• It allows insects to float and slide on the water's surface, usually denser than water
• The molecules at the surface have an unbalanced force rather than molecules at deeper and the resultant force moves downward this is surface tension.

Concept:

Surface tension on a liquid droplet (Spherical droplet of water): Pressure intensity inside the droplet:

\(p = \frac{{4\sigma }}{d}\)

Surface tension on a hollow bubble (Soap bubble): Pressure intensity inside the droplet:

\(p = \frac{{8\sigma }}{d}\)

where σ is the surface tension of the liquid.

Calculation:

\({\rm{\Delta }}P = \frac{{8\sigma}}{d}\)

\(\sigma = \frac{{\Delta P\times d}}{8 } =\frac{{3\times 0.080}}{8 }= 0.03 \; N/m\)

Explanation:

Surface Tension: It is defined as force per unit length in the plane of the liquid surface at right angles to either side of an imaginary line drawn to the surface.

Mathematically, 

\(\rm Surface\;Tension = \frac{{Force}}{{Length}}\)

• It is the tendency of the liquid surface to shrink into a minimum surface area.
• The SI Unit of surface tension is N m-1
• It allows insects to float and slide on the water surface, usually more dense than water
• The molecules at the surface have unbalanced force rather than molecules at deeper and the resultant force moves downward this is surface tension.
• The dimensional formula is MT-2