Due to capillary action, a liquid will rise in a tube, if the angle of contact is

Options

A. acute obtuse
B. obtuse
C. `90^(@)`
D. zero

Explanation

To determine the conditions under which a liquid will rise in a tube due to capillary action, we need to analyze the relationship between the angle of contact (also known as the contact angle) and the behavior of the liquid in the tube.

### Step-by-Step Solution:

1. **Understanding Capillary Action**:
Capillary action occurs when a liquid rises or falls in a narrow space, such as a tube, due to the interplay of cohesive forces (between liquid molecules) and adhesive forces (between liquid molecules and the surface of the tube).

2. **Contact Angle**:
The contact angle (θ) is the angle formed between the tangent to the liquid surface and the solid surface at the point of contact. It determines how well the liquid wets the surface of the tube.

3. **Conditions for Rising**:
- If the contact angle θ is less than 90 degrees (acute angle), the adhesive forces between the liquid and the tube are stronger than the cohesive forces within the liquid. This results in the liquid climbing up the tube.
- If θ is equal to 90 degrees, the liquid will neither rise nor fall; it will remain at the same level.
- If θ is greater than 90 degrees (obtuse angle), the cohesive forces dominate, and the liquid will not rise in the tube.

4. **Conclusion**:
Therefore, for a liquid to rise in a tube due to capillary action, the angle of contact must be acute (θ < 90 degrees).

### Final Answer:
The liquid will rise in a tube due to capillary action if the angle of contact is acute (θ < 90 degrees).

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