Bissoy.com
Doctors Medicines MCQs Q&A

A liquid is filled in a capillary tube. The angle of contact is 90° between the wall of the capillary tube and liquid. Then which one of the following statements is correct? 

A liquid is filled in a capillary tube. The angle of contact is 90° between the wall of the capillary tube and liquid. Then which one of the following statements is correct?  Correct Answer Cohesive force = Adhesive force

CONCEPT:

  • Contact angle: The contact angle is a measure of the ability of a liquid to wet the surface of a solid. 
  • Adhesive forces: Attractive forces between molecules of different types are called adhesive forces.
  • Cohesive forces: Attractive forces between molecules of the same types are called cohesive forces.
  • For contact angle 90° the cohesive forces and adhesive forces are in the equilibrium state.



[ alt="F1 J.K Madhu 19.05.20 D5" src="//storage.googleapis.com/tb-img/production/20/05/F1_J.K_Madhu_19.05.20_D5.png" style="width: 292px; height: 144px;">

EXPLANATION:

  • When the cohesive and adhesive forces are equal in magnitude then the contact angle between the surface of the tube and liquid is 90°. So option 2 is correct.

[ alt="Group X ST 5 Physics.docx 1" c: log point.png src="//storage.googleapis.com/tb-img/production/20/05/Group%20X_%20ST%205_Physics.docx%201.PNG" style="width: 163px; height: 62px;">

  • The angle between 0 ° and 90 ° = surface wettable, hydrophilic, cohesive forces are weaker then adhesive forces.
  • The angle between 90 ° and 180 ° = surface not wettable, hydrophobic cohesive forces are stronger than adhesive forces
  • The angle is close to 180 ° = ultra-hydrophobic surface, completely liquid-repellent, lotus effect.
  • The contact angle is 90° between water and silver, cohesive forces and adhesive forces are equal.

Related Questions

One end of the ladder is in contact with a wall and the other end is in contact with level ground making an angle of 40° when the foot of the ladder is moved through a distance ‘x’ m away from the wall, the end in contact with wall sides ‘3m’ along the wall and the angle made by the ladder with the level is, now 20°. Then, find the value of x?
The angle of contact between a glass capillary tube of length 10 cm and a liquid is 90 degree . If the capillary tube is dipped vertically in the liquid, then the liquid:
The angle of contact between a glass capillary tube of length 10 cm and a liquid is 90 Degree. If the capillary tube is dipped vertically in the liquid, then the liquid:
Consider a capillary tube in which water has risen. The contact angle is θ. The radius of the capillary tube is ‘r’. The surface tension is ‘S’. And the density of water is ‘ρ’. What is the expression for the height of water risen in the tube? Assume the radius of meniscus to be ‘R’. Let the height of water risen in the tube be ‘h’.
Consider the following statements: In case of helical gears, teeth are cut at an angle to the axis of rotation of the gears. 1) Helix angle introduces another ratio called axial contact ratio. 2) Transverse contact ratio is equal to axial contact ratio in helical gears. 3) Large transverse contact ratio does not allow multiple teeth to share the load. 4) Large axial contact ratio will cause larger axial force component Which of the above statements are correct?
A large tank of height h is half-filled with a liquid of density ρ and other half-filled with a liquid of density 4ρ. A similar tank is half-filled with a liquid of density 2ρ and other-half filled with another liquid of density 3ρ as shown. What will be the ratio of the instantaneous velocities of discharge through a small opening at the base of the tanks? (assume that the diameter of the opening is negligible compared to the height of the liquid column in either of the tanks)
In a capillary tube experiment, a vertical, 30 cm long capillary tube is dipped in water. The water rises up to a height of 10 cm due to capillary action. If this experiment is conducted in a freely falling elevator, the length of the water column becomes ___________
I. All the offices on the 9th floor have wall-to-wall carpeting. II. No wall-to-wall carpeting is pink. III.None of the offices on the 9th floor has pink wall-to-wall carpeting. If the first two statements are true, the third statement is
If the first two statements are true, the third statement is :
I. All the offices on the 9th floor have wall-to-wall carpeting.
II. No wall-to-wall carpeting is pink.
III. None of the offices on the 9th floor has pink wall-to-wall carpeting.
A retaining wall 6m high supports a backfill with a surcharge angle of 10°. The back of the wall is inclined to the vertical at a positive batter angle of 5°. If the angle of wall friction is 7°, then the resultant active earth pressure will act at a distance of 2 m above the base and inclined to the horizontal at an angle of