A rectangular soap film is formed on a wire frame. The work done in increasing the size of the film from 10 cm 5 cm to 10 cm 8 cm is: (Surface tension of the soap solution is 0.04 N m ⁻¹ )

Step-by-step solution

Initial area of the soap film, A₁ = 10 cm 5 cm = 50 cm ^2 = 50 10⁻⁴ m ^2 Final area of the soap film, A₂ = 10 cm 8 cm = 80 cm ^2 = 80 10⁻⁴ m ^2 Change in area, A = A₂ - A₁ = 80 10⁻⁴ - 50 10⁻⁴ = 30 10⁻⁴ m ^2 Since a soap film has two free surfaces, the total increase in surface area is 2 A . Work done, W = T 2 A W = 0.04 2 30 10⁻⁴ W = 2.4 10⁻⁴ J Answer: 2.4 10⁻⁴ J