Surface Energy and Surface Tension (Angle of Contact, Excess of Pressure Across a Curved Surface, Application of Surface Tension - Drops, Bubbles, and Capillary Rise...) NEET Questions

Physics - Properties of Solids and Liquids

Surface Energy and Surface Tension (Angle of Contact, Excess of Pressure Across a Curved Surface, Application of Surface Tension - Drops, Bubbles, and Capillary Rise...) MCQ Questions


13.
An air bubble of radius r inside a liquid has excess pressure:
A.
P_i − P_o = S/r
B.
P_i − P_o = 6S/r
C.
P_i − P_o = 4S/r
D.
P_i − P_o = 2S/r
😑 View Answer Rough Work Error
ANSWER :
D. P_i − P_o = 2S/r
14.
Which of the following correctly orders excess pressure (smallest to largest) for: (A) liquid drop, (B) air bubble in liquid, (C) soap bubble, all of radius r?
A.
A < C < B
B.
C < A = B
C.
A = B < C
D.
A < B < C
😑 View Answer Rough Work Error
ANSWER :
C. A = B < C
15.
In capillary rise, water (contact angle θ) rises in a narrow tube of radius a. The capillary rise height h is:
A.
h = 2S cosθ/(ρga)
B.
h = 4S cosθ/(ρga)
C.
h = S cosθ/(ρga)
D.
h = Sρg/(2a cosθ)
😑 View Answer Rough Work Error
ANSWER :
A. h = 2S cosθ/(ρga)
16.
The capillary rise formula h = 2S cosθ/(ρga) shows that rise is inversely proportional to tube radius a. This means:
A.
Narrower capillaries show greater rise — rise ∝ 1/a
B.
Rise equals zero in very narrow tubes
C.
Radius has no effect on capillary rise
D.
Wider capillaries show greater rise
😑 View Answer Rough Work Error
ANSWER :
A. Narrower capillaries show greater rise — rise ∝ 1/a
17.
For a capillary tube with a = 0.05 cm in water (S = 0.073 N/m, ρ = 10³ kg/m³, θ ≈ 0°, g = 9.8 m/s²), the capillary rise is approximately:
A.
2.98 m
B.
0.0298 m
C.
0.298 m
D.
298 m
😑 View Answer Rough Work Error
ANSWER :
B. 0.0298 m
18.
When mercury is placed in a capillary tube, the mercury level inside is LOWER than outside. The reason is:
A.
Mercury has higher density
B.
Mercury is a metal
C.
Mercury has zero surface tension
D.
For mercury on glass, angle of contact θ is obtuse (cosθ < 0) → h = 2S cosθ/(ρga) < 0 → capillary depression
😑 View Answer Rough Work Error
ANSWER :
D. For mercury on glass, angle of contact θ is obtuse (cosθ < 0) → h = 2S cosθ/(ρga) < 0 → capillary depression