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The surface tension of a soap solution is ' $\mathrm{T}$ '. Work done in blowing a soap bubble of diameter $2 \mathrm{~d}$ is
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The correct answer is:
$8 \pi d^2 T$
In this case, work done = increase in surface energy, i.e.
$\mathrm{W}=\mathrm{T} \Delta \mathrm{A}$
Key point: In calculation, area of sphere have been multiplied with 2, since there are two surfaces in soap bubble.
$\begin{aligned} & \therefore \mathrm{W}=\mathrm{T} \times\left[2\left(4 \pi \mathrm{d}^2\right)\right] \\ & \Rightarrow \mathrm{W}=8 \pi \mathrm{d}^2 \mathrm{~T}\end{aligned}$
$\mathrm{W}=\mathrm{T} \Delta \mathrm{A}$
Key point: In calculation, area of sphere have been multiplied with 2, since there are two surfaces in soap bubble.
$\begin{aligned} & \therefore \mathrm{W}=\mathrm{T} \times\left[2\left(4 \pi \mathrm{d}^2\right)\right] \\ & \Rightarrow \mathrm{W}=8 \pi \mathrm{d}^2 \mathrm{~T}\end{aligned}$
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