A soap bubble of radius r is blown up to form a bubble of radius 2 r under isothermal conditions. If σ is the surface tension of the soap solution, the energy spent in the process is

Question

A soap bubble of radius r is blown up to form a bubble of radius 2 r under isothermal conditions. If σ is the surface tension of the soap solution, the energy spent in the process is, 6 π σ r 2, 24 π σ r 2, 12 π σ r 2, 9 π σ r 2

MARKS App · Accepted Answer

Energy spent = Work done = T ∆ A Here, A is total surface area ∴ A = 8 π r 2 for soap bubble Hence, energy spent = σ 8 π 2 r 2 - 8 π r 2 = σ 32 π r 2 - 8 π r 2 = 24 π σ r 2

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