Question

1.A water film is made between two straight parallel wires of length 10 cm each and at a distance of 0.5
cm from each other. If the distance between the wire is increased by 1mm, how much work will be
done ? Surface tension of water = 72 dynes/cm
(A)
288 ergs
(B) 72 ergs (C)
144 ergs
(D)
216 ergs​

Answer 1

Answer:

By increasing the distance between the wires by 1 mm the increase in area of the film. ΔA = 2 × 0.1 × 10–3 = 2 × 10–4 m2 (Film has two surfaces)

Work done = TΔA

= 72 × 10–3 × 2 × 10–4 J

= 144 × 10–7 J = 1.44 × 10–5 J

options C is correct

Answer 2

Answer:

c

it is the correct answer