Question

If work done in increasing the size of a soap film from $10cm\times 6cm$ to $60cm$ is $2\times {10}^{-4}$.
What is the surface tension ?

• A. $2\times {10}^{-8}{Nm}^{-1}$
• B. $2\times {10}^{-2}{Nm}^{-1}$
• C. $2\times {10}^{-4}{Nm}^{-1}$
• D. None of these

Answer 1

The correct option is D None of these

Potential energy stored in a surface $A$ with surface tension $T=TA$

Hence work done in increasing the area=$T{A}_2-T{A}_1=T\times 2(A_2-A_1)$

$=2\times {10}^{-4}=T(660-60)\times {10}^{-4}$

$⟹T=\frac{1}{600}N{m}^{-1}$