1) Aim
2) Apparatus
3) Diagram
4) Formula with explanation/law
5) Theory
6) Observations
7) Observation Table
8) Calculation
9) Result/Conclusion
10) Precautions
11) Questions
12) Graph
आता आपण Experiment चे Solutions पाहण्यास सुरुवात करुया :-
Class 12 Physics Practical No 2 : Surface Tension Solutions Maharashtra Board
[Page No 17]
Aim :
To determine the surface tension of the given liquid (water) by capillary rise method.
Apparatus :
Travelling microscope, beaker, capillary tube, cork with pointer, stand with clamp, water.
Diagram :
Theory :
At N.T.P, when a liquid (water) rises in a capillary tube the weight of the column of the water of density ρ (ρ=1) below the meniscus is supported by the up ward force of surface tension acting around the circumference of the point of contact. Therefore Approximately,
(for water) 2πrT = πr²hρg or T = hρgr/2
[Page No 18]
Formula :
T = hrg/2
Where, T = surface tension of liquid
h = height of liquid column in capillary tube
r = inner radius of the cross section of bore of the capillary
ρ = density of the liquid (water)
θ = angle of contact between water and glass
For water, ρ = 1.0 g/cm³
Angel of contact between water and glass is very small.
i.e. θ = 0°, cosθ = 1
Observation :
Least count (L.C.) of travelling microscope:
| Smallest division of main scale (P) | 0.05 cm |
| Total no. of divisions on the vernier scale (N) | 50 |
| L.C. of travelling microscope (P/N) | 0.001 |
[Page No 19]
Observation Tables :
1) Measurement of radius of bore (r) :
| Obs. No. |
Reading when crosswire is tangential to |
Diameter of bore d=x-y cm |
mean diameter d cm |
mean radius r cm |
||
|---|---|---|---|---|---|---|
| one side of the bore x cm |
other side of the bore y cm |
|||||
| Reading along diameter |
1 | 11.083 | 10.917 | d1 = 0.166 | r1 = 0.083 | 0.072 |
| 2 | 11.077 | 10.924 | d1' = 0.153 | r1' = 0.076 | ||
| Reading along perpendicular to diameter |
1 | 12.471 | 12.341 | d2 = 0.130 | r2 = 0.065 | |
| 2 | 12.465 | 12.336 | d2' = 0.129 | r2' = 0.065 | ||
2) Measurement of capillary rise (h) :
| Obs. No. |
Reading when the microscope is focused on | Capillary rise h=h1-h2 cm |
Mean Capillary rise h cm |
|||||
|---|---|---|---|---|---|---|---|---|
| The meniscus h1 cm | the tip of the pointer h2 cm | |||||||
| MSR | VSR | h1 | MSR | VSR | h2 | |||
| a cm | n | a+n*L.C | bcm | n | b+n*L.C | |||
| 1 | 6.676 | 26 | 6.676 | 5.312 | 12 | 5.312 | 1.364 | 1.364 |
| 2 | 6.711 | 11 | 6.711 | 5.325 | 25 | 5.325 | 1.386 | |
Calculation :
T = hrρg/2 where ρ = 1 g/cm³
T = hrg/2
= 48.12 dyne/cm
= 0.04812 N/m
Result :
Surface tension of given liquid (water)
T = 48.12 dyne/cm = 0.04812 N/m
Precautions :
1) The capillary should be thoroughly cleaned.
2) There should be no air bubbles inside the capillary. Capillary must be immersed in the liquid.
3) The capillary should be vertical.
[Page No 20]
Questions :
1) Define angle of contact.
Ans : Angle of contact is the angle between the tangent to the liquid surface and the solid surface in contact with the liquid.
2) List the factors affecting surface tension.
Ans : Factors affecting surface tension: Temperature, nature of the liquid, and presence of dissolved substances.
3) Why should the capillary be cleaned every time before use?
Ans : The capillary should be cleaned before use to remove any contaminants or residues that could affect the accuracy of measurements and ensure reliable and consistent results.
4) Where do you observe capillary action in day to day life?
Ans : Capillary action is observed in day-to-day life when water is drawn up through a paper towel or a sponge, or when liquid ink rises through the fibers of a fountain pen.
अशा प्रकारे मित्रांनो आपण इयत्ता बारावी Physics Practical Number 2 - Surface Tension याचे Solutions पहिले.
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