1. For a liquid surface, surface energy per unit area is equal to which quantity?
A.
Surface tension
B.
Density
C.
Pressure
D.
Viscosity
Correct Answer:
Surface tension
Explanation:
Surface energy per unit area is numerically equal to the surface tension of the liquid.
2. The surface energy E of a liquid surface having area A and surface tension T is given by:
A.
E = T/A
B.
E = A/T
C.
E = TA
D.
E = T + A
Correct Answer:
E = TA
Explanation:
Surface energy equals surface tension multiplied by the surface area, so E = TA.
3. The SI unit of surface energy per unit area is:
A.
N/m
B.
N m
C.
Pa/m
D.
J m
Correct Answer:
N/m
Explanation:
Surface energy per unit area has the same unit as surface tension, which is N/m. It is also equivalent to J/m².
4. A liquid surface has surface tension 0.05 N/m and area 2 m². Its surface energy is:
A.
0.025 J
B.
0.10 J
C.
2.05 J
D.
40 J
Correct Answer:
0.10 J
Explanation:
Using E = TA, the surface energy is 0.05 × 2 = 0.10 J.
5. When the area of a liquid surface is increased at constant surface tension, its surface energy:
A.
Decreases
B.
Remains zero
C.
Increases
D.
Becomes independent of area
Correct Answer:
Increases
Explanation:
Since E = TA, surface energy increases when surface area increases, provided surface tension remains constant.
6. A soap film has two surfaces. If each surface has area A and surface tension T, the total surface energy of the film is:
A.
TA
B.
2TA
C.
T/A
D.
A/2T
Correct Answer:
2TA
Explanation:
A soap film has two liquid surfaces, and each contributes energy TA. Therefore, total surface energy is 2TA.
7. Surface tension can be expressed in terms of surface energy E and area A as:
A.
T = EA
B.
T = E/A
C.
T = A/E
D.
T = E + A
Correct Answer:
T = E/A
Explanation:
From the relation E = TA, dividing by area gives T = E/A.
8. The work required to increase the area of a single liquid surface by ΔA is:
A.
T/ΔA
B.
ΔA/T
C.
TΔA
D.
T + ΔA
Correct Answer:
TΔA
Explanation:
The increase in surface energy, and hence the work required, is ΔE = TΔA for a single surface.
9. Which statement correctly relates surface tension and surface energy per unit area?
A.
They are numerically equal
B.
Surface tension is always twice the surface energy per unit area
C.
Surface energy per unit area is always zero
D.
They have unrelated values and units
Correct Answer:
They are numerically equal
Explanation:
For a liquid surface, surface tension is equal in magnitude to surface energy per unit area.
10. If the surface area of a single liquid surface is doubled while surface tension remains constant, its surface energy becomes:
A.
Half
B.
Unchanged
C.
Double
D.
Four times
Correct Answer:
Double
Explanation:
Because surface energy is E = TA, doubling the area doubles the surface energy when T is constant.
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