Lab no 1: Capillary elevation in capillary tubes

Part I:

Location:

UDC, engineering building, C level

Objective:

Measurement of the capillary elevation inside the capillary tubes.

Equipment:

  • Glass capillary tubes
  • Wetting agent
  • Pencil and water proof card
  • Methylated spirits

Method:

By immersing different capillary tubes of different diameters in the water and measure the elevation of level inside the tube due to surface tension.

Procedure:

  • When a tube of small bore is inserted inside the water the water level may rise or fall, depending upon the contact between the surface tubes.
  • Now put each tube and measure the water level in case of each tube.
  • When water level rises by the insertion of tubes, focus a small meniscus around the tube.
  • Record the elevation in case of each tube, smaller the bore greater the elevation. Use a card to measure the rise of water. Calculate the rise of each tube using

 

Results:

ID of capillary tube mm Measured rise h(mm) Calculated rise h(mm)
0.5 22 59
0.8 18 37
1.1 16 27
1.7 15 17
2 13 15
2.2 12 13

 

Calculations:

Using the formula

height of each tube is calculated. By putting the = 0.072N/m at 25 oC

Plot:

between the measured rise and the ID of capillary tube

 

Conclusion:

As the diameter of the bore increases the height of rise of water decreases. There was an error observed between the measured and the observed measurements, the error was due to the change in the atmospheric pressure.

Advantages:

It is very easy to handle and no wear and tear. Also it has no moving parts.

Disadvantages:

It cannot adjust itself by the change of flow conditions.

 

 

 

 

PART II:

Capillary Elevation between Plates

Location:

UDC, engineering building, C level

Objective:

To demonstrate the effect of capillary elevation between the flat glasses due to surface tension.

Equipment:

  • Flat glass plates
  • Wetting agent
  • Pencil and water proof card
  • Methylated spirits

Method:

By creating gap between two vertical plates and observing the rise of water.

Procedure:

  • Fill water in the trough.
  • If required insert cards behind the plates to see the water level.
  • Repeat the experiment by using different diameters.
  • As the surface tension changes by changing the temperature so the exercise can be repeated by temperatures.

Results for part 2 are missing

 

PART III

Archimedes’ Principle

 

Objective:

Verification of Archimedes principle using brass bucket and a cylinder with a lever balance and displacement vessel.

Equipment:

  • Lever balance
  • Displacement balance
  • Optional equipment

 

Method:

Weighing of machined bucket and cylinder in air and immersed in the water in order to measure the up thrust and the displacement volume.

Procedure:

  • Suspend the bucket and cylinder by a fine thread.
  • By the balance set to operate on the 0-25gm.
  • Fill the displacement vessel with water than allow it to drain to the level of spout on the side.
  • Immerse the cylinder completely in the displacement vessel.
  • Allow the displaced water to collect in the container than remove the beaker.
  • Remove the cylinder and note down the mass of the bucket.

Results:

Items units results
Mass of bucket with cylinder in air Grams m1 = 185
Mass of bucket immersed in water Grams m2 = 180
Upthrust force Newtons 0.05
Mass of bucket only in air grams m3 = 100
Mass of bucket filled with water Grams m4 = 105.2
Mass of water grams m4 – m3 =5.2
Gravitational force on the mass of water Newtons  

 

Conclusion:

m1 – m2 = m4-m3

185-180 = 5.2

5   = 5.2

Hence proved the Archimedes’ principle.