MCQ
The surface tension of a liquid is $5\, N/m$. If a thin film of the area $0.02\, m^2$ is formed on a loop, then its surface energy will be
  • A
    $5 \times {10^2}\,J$
  • B
    $2.5 \times {10^{ - 2}}\,J$
  • $2 \times {10^{ - 1}}\,J$
  • D
    $5 \times {10^{ - 1}}\,J$

Answer

Correct option: C.
$2 \times {10^{ - 1}}\,J$
c
(c) $W = T \times \Delta A = 5 \times 2 \times (0.02)$ (Film has two free surfaces)
$ = 2 \times {10^{ - 1}}J$

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