A water film is formed between the two straight parallel wires, each of length \(10~\text{cm}\), kept at a separation of \(0.5~\text{cm}.\)Now, the separation between them is increased by \(1~\text{mm}\) without breaking the water film. The work done for this is
(surface tension of water =\(7.2\times 10^{-2}~\text{N/m}\))
1. \(7.22\times 10^{-6}~\text{J}\)
2. \(1.44\times 10^{-5}~\text{J}\)
3. \(2.88\times 10^{-5}~\text{J}\)
4. \(5.76\times 10^{-5}~\text{J}\)

A drop of mercury of radius 2 mm is split into 8 identical droplets. Find the increase in surface energy. (Surface tension of mercury is $0.465 \mathrm{J}/{\mathrm{m}}^2$) 

(1)$23.4 \mathrm{\mu J}$

(2) $18.5 \mathrm{\mu J}$

(3) $26.8 \mathrm{\mu J}$

(4) $16.8 \mathrm{\mu J}$

Two small drops of mercury, each of radius r, coalesce to form a single large drop. The ratio of the total surface energies before and after the change is

1. $1:2^{1/3}$

2. $2^{1/3} :1$

3. 2:1

4. 1:2

If two soap bubbles of equal radii r coalesce then the radius of curvature of interface between two bubbles will be

(1) r                                 

(2) 0

(3) Infinity                         

(4) 1/2r

The angle of contact between glass and mercury is

(1) 0°

(2) 30°

(3) 90°

(4) 135°

A mercury drop does not spread on a glass plate because the angle of contact between glass and mercury is

(1) Acute

(2) Obtuse

(3) Zero

(4) $90°$

The liquid meniscus in the capillary tube will be convex if the angle of contact is

(1) Greater than 90°

(2) Less than 90°

(3) Equal to 90°

(4) Equal to 0°

The value of contact angle for kerosene with a solid surface.

(1) 0°

(2) 90°

(3) 45°

(4) 33° 

Nature of meniscus for liquid of $0^0$ angle of contact

(1) Plane

(2) Parabolic

(3) Semi-spherical

(4) Cylindrical

A liquid wets a solid completely. The meniscus of the liquid in a sufficiently long tube is 

(1) Flat

(2) Concave

(3) Convex

(4) Cylindrical