1. Tardigrade
  2. Question
  3. Physics
  4. A frame made of metallic wire enclosing a surface area A is covered with a soap film. If the area of the frame of metallic wire is reduced by 50 %, the energy of the soap film will be changed by

Question Error Report

Thank you for reporting, we will resolve it shortly

Back to Question

Q. A frame made of metallic wire enclosing a surface area $A$ is covered with a soap film. If the area of the frame of metallic wire is reduced by $50\%$, the energy of the soap film will be changed by

UP CPMTUP CPMT 2008

Solution:

Surface energy = Surface tension $\times$ surface area
$E=T\times 2A$ (Since the soap film has two surfaces)
$A'=[A-\frac{50\,A}{100}]=\frac{A}{2}$
$\therefore E'=T\times 2 \left(\frac{A}{2}\right)$
$E'=T\times A$
Percentage decrease in surface energy
$=\frac{E-E'}{E}\times100$
$=\frac{2TA-TA}{2TA}\times100$
$=\frac{1}{2}\times100$
$=50\%$