Physics Tutor in Sector 119 Noida by Kumar Physics Classes with capillary rise ascent formula derivation

Physics Tutor in Sector 119 Noida | Kumar Physics Classes

+91-9958461445

If you live in Sector 119 Noida and Physics is not making sense to you, then you are not alone. Many students of Class 11 and Class 12 face the same problem. They go to school, attend classes, meet friends, spend time in social activities, but when Physics marks come, the result is not satisfactory.

The real problem is not that the student is weak. The real problem is that Physics is not taught with proper concept clarity. If the teacher does not explain the basic idea, derivation, formula, application and numerical approach, then the student starts feeling that Physics is very difficult.

At Kumar Physics Classes, Kumar Sir teaches Physics with a proper textbook-based and exam-oriented approach. Students are guided for CBSE Physics, ICSE Physics, NEET Physics, JEE Physics, AP Physics, IB Physics, IGCSE Physics, A-Level Physics and British Curriculum Physics.

Website: Kumar Physics Classes
Contact: +91-9958461445
Email: kumarsirphysics@gmail.com

Why Students in Sector 119 Noida Need Proper Physics Guidance

Many students waste time in random tuition, random online videos and incomplete notes. After a few months, they realise that concepts are still not clear. Physics cannot be learned only by watching shortcuts. Physics needs:

Concept clarity
Proper derivation
Formula understanding
Numerical practice
Diagram-based learning
Regular revision
Exam-oriented preparation

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Noida Sector Wise Physics Tutor Links

School Wise Physics Tutor Links in Noida

Capillary Rise Formula

When a narrow capillary tube is dipped in water or any liquid, the liquid may rise or fall inside the tube. This phenomenon is called capillary action.

For water in a glass tube, water rises because adhesive force between water and glass is greater than cohesive force between water molecules.

Formula of Capillary Rise

The height of liquid rise in a capillary tube is:

h = 2T cos theta / r rho g

Where:

h = height of rise of liquid
T = surface tension of liquid
theta = angle of contact
r = radius of capillary tube
rho = density of liquid
g = acceleration due to gravity

Derivation of Capillary Rise Formula

Consider a capillary tube of radius r dipped vertically in a liquid.

The liquid rises to height h inside the tube.

The upward force due to surface tension acts along the circumference of the liquid meniscus.

Circumference of tube = 2 pi r

Surface tension force along the liquid surface = T x 2 pi r

Only vertical component supports the liquid column.

Vertical upward force = 2 pi r T cos theta

Now, weight of liquid column inside the capillary tube:

Volume of liquid column = pi r^2 h

Mass of liquid column = volume x density

Mass = pi r^2 h rho

Weight = pi r^2 h rho g

At equilibrium:

Upward force due to surface tension = Weight of liquid column

2 pi r T cos theta = pi r^2 h rho g

Cancel pi r from both sides:

2T cos theta = r h rho g

Therefore:

h = 2T cos theta / r rho g

This is the formula for capillary rise.

Important Points from the Formula

h = 2T cos theta / r rho g

From this formula:

Height of rise is directly proportional to surface tension.

h proportional to T

Height of rise is inversely proportional to radius of capillary tube.

h proportional to 1/r

If radius is small, liquid rises more.
If radius is large, liquid rises less.
If angle of contact is acute, liquid rises.
If angle of contact is obtuse, liquid falls.
For water and glass, theta is small, so water rises.
For mercury and glass, theta is obtuse, so mercury falls.

Simple Diagram for Capillary Rise

        Capillary Tube
             |
             |
             |      Liquid rises to height h
             |          ↑
             |          |
             |          h
             |          |
        _____|__________
       |     |          |
       |     |          |
       |_____|__________|
          Liquid Surface

Radius of tube = r
Surface tension = T
Angle of contact = theta

Final Note

If you are searching for Physics Tutor in Sector 119 Noida, Kumar Physics Classes can help students understand Physics with proper logic, derivation and numerical practice.

Physics becomes easy when it is taught by an experienced teacher who explains every concept step by step.

Website: Kumar Physics Classes
Contact: +91-9958461445
Email: kumarsirphysics@gmail.com

40 Conceptual Theory Questions on Capillary Rise Formula with Answers

1. What is capillary rise?

Answer:
Capillary rise is the phenomenon in which a liquid rises inside a narrow tube due to surface tension.

2. What is the formula for capillary rise?

Answer:
The formula is:

h = 2T cos theta / r rho g

Where h is height of rise, T is surface tension, theta is angle of contact, r is radius of tube, rho is density of liquid, and g is acceleration due to gravity.

3. Why does liquid rise in a capillary tube?

Answer:
Liquid rises because the upward force due to surface tension balances the weight of the liquid column.

4. What is the main force responsible for capillary rise?

Answer:
Surface tension is the main force responsible for capillary rise.

5. What does h represent in the formula?

Answer:
h represents the height to which the liquid rises in the capillary tube.

6. What does T represent in the formula?

Answer:
T represents the surface tension of the liquid.

7. What does theta represent in the formula?

Answer:
Theta represents the angle of contact between the liquid and the wall of the tube.

8. What does r represent in the formula?

Answer:
r represents the radius of the capillary tube.

9. What does rho represent in the formula?

Answer:
Rho represents the density of the liquid.

10. What does g represent in the formula?

Answer:
g represents acceleration due to gravity.

11. How does capillary rise depend on radius?

Answer:
Capillary rise is inversely proportional to the radius of the tube.

If radius increases, height decreases.
If radius decreases, height increases.

12. How does capillary rise depend on surface tension?

Answer:
Capillary rise is directly proportional to surface tension.

If surface tension increases, height increases.

13. How does capillary rise depend on density?

Answer:
Capillary rise is inversely proportional to density.

If density increases, height decreases.

14. How does capillary rise depend on gravity?

Answer:
Capillary rise is inversely proportional to acceleration due to gravity.

If gravity increases, height decreases.

15. Why does water rise in a glass capillary tube?

Answer:
Water rises because adhesive force between water and glass is greater than cohesive force between water molecules.

16. Why does mercury fall in a glass capillary tube?

Answer:
Mercury falls because cohesive force between mercury molecules is greater than adhesive force between mercury and glass.

17. What happens when angle of contact is acute?

Answer:
When angle of contact is acute, cos theta is positive, so the liquid rises in the capillary tube.

18. What happens when angle of contact is obtuse?

Answer:
When angle of contact is obtuse, cos theta is negative, so the liquid falls in the capillary tube.

19. What happens when theta is 90 degrees?

Answer:
When theta is 90 degrees, cos theta = 0, so there is no rise or fall of liquid.

20. Why is the tube called a capillary tube?

Answer:
It is called a capillary tube because it has a very small radius or very narrow bore.

21. Why is capillary rise more in a thinner tube?

Answer:
In a thinner tube, radius is smaller. Since h is inversely proportional to r, the liquid rises more.

22. Why is capillary rise less in a wider tube?

Answer:
In a wider tube, radius is larger. Since h is inversely proportional to r, the liquid rises less.

23. What balances the upward surface tension force?

Answer:
The weight of the liquid column balances the upward surface tension force.

24. What is the upward force due to surface tension?

Answer:
The upward force is:

2 pi r T cos theta

25. What is the weight of the liquid column?

Answer:
The weight of the liquid column is:

pi r^2 h rho g

26. Why do we take vertical component of surface tension?

Answer:
Only the vertical component of surface tension supports the weight of the liquid column.

27. Why is cos theta used in the formula?

Answer:
Cos theta is used because the vertical component of surface tension is T cos theta.

28. What happens to capillary rise on the Moon?

Answer:
On the Moon, gravity is smaller, so capillary rise is greater.

29. What happens to capillary rise if surface tension becomes zero?

Answer:
If surface tension becomes zero, capillary rise becomes zero.

30. Does capillary rise depend on atmospheric pressure?

Answer:
In the basic formula, capillary rise does not directly depend on atmospheric pressure.

31. Does capillary rise depend on the material of the tube?

Answer:
Yes, because the material affects the angle of contact between liquid and tube.

32. Why does oil rise differently from water?

Answer:
Oil has different surface tension, density and angle of contact, so its capillary rise is different.

33. Why is capillary action important in plants?

Answer:
Capillary action helps water rise through narrow tubes in plant stems.

34. Why does blotting paper absorb ink?

Answer:
Blotting paper has tiny pores that act like capillary tubes, so ink rises into them due to capillary action.

35. Why does a towel absorb water?

Answer:
A towel has many fine spaces between fibres that behave like capillary tubes.

36. What is capillary depression?

Answer:
Capillary depression is the lowering of liquid level in a capillary tube, as seen with mercury in glass.

37. What is the condition for capillary rise?

Answer:
Capillary rise occurs when adhesive force is greater than cohesive force and angle of contact is less than 90 degrees.

38. What is the condition for capillary depression?

Answer:
Capillary depression occurs when cohesive force is greater than adhesive force and angle of contact is greater than 90 degrees.

39. Why is the meniscus concave for water in glass?

Answer:
The meniscus is concave because water wets glass and adhesive force is stronger than cohesive force.

40. Why is the meniscus convex for mercury in glass?

Answer:
The meniscus is convex because mercury does not wet glass and cohesive force is stronger than adhesive force.